What is "Headspace"?

[1911Tuner]

Oh Lord...Give me Strength

We ain't gonna do this, Bill...There's already been way too much bandwidth
used in arguing a simple but critical procedure that could have been verified by simply looking in the back of a reloading manual for the definition of the term...but in the spirit of good debate and reliable information, I'll outline it just once more.

SAAMI standard cartridge case length for the .45 ACP is .898 minus .010 inch.

The Minimum GO gauge was established at that length to insure that the longest case will go into battery reliably in a minimum-dimension chamber.
The directive is that: "All pistols must go into battery on the minumum gauge."

The maximum headspace allowable for the cartridge is .022 inch which sets the maximum dimension at .920 inch. Maximum.

The directive is: Any pistol that chambers and goes to battery on the
maximum NO GO is deemed unserviceable and must be repaired before being accepted.

The reasons are:

1...Possible unreliable ignition, due to the case rim and primer being located too far forward of the breechface, or the round moving deeper into the chamber before stopping on the shoulder when the firing pin strikes it.

2...Overstressing and possible premature failure of the extractor hook in the event of a condition known as headspacing and firing on the extractor. (A .45 GAP round will chamber, fire and function in a .45 ACP chamber because of this condition.)

3...Possibility of case head blowout due to the case backing up in the chamber under peak pressures when the round is fired. I've seen this occur 3 times, and in neither instance was the barrel throated to the point of a condition of insufficient head support.

Note that excessive headspace isn't necessarily dangerous...as in the case of the chamber simply being too long, and creating the condition of headspacing
and/or firing on the extractor. Here...it's mainly a nuisance and a possible source of misfires and broken parts.

HOWEVER...If the excessive headspace is created because of the location of
the barrel relative to the breechface, resulting in an excessive gap between
the rim and the slide when the cartridge is fully forward in the chamber and
stopped by the mouth of the case touching the chamber shoulder...the round
will back up under pressure until it stops on the slide. The case head then becomes unsupported, possibly to the point of blowout. The effect is much the same as cutting away the bottom of the chamber, such as we see so much as a result of the "Dude with a Dremel" syndrome doing a "Throat Job"
without understanding what is involved.

MOREOVER...The danger lies not so much in the round blowing out in front of the case head...but in the real and distinct possiblilty of sympathetic detonation of the rounds remaining in the magazine. The 1911 is strong enough to withstand one round blowing out in the port. The real fireworks begin when the ones held in the magazine become involved. Imagine, if you will...two or three miniature fragmentation devices detonating in your hand with just a panel of quarter-inch thick wood and sheet metal standing between them.

The .45 is a low-pressure round...but it still operates at some 20,000 psi.
There are also our eyes to consider in the equation...not to mention my chiseled, handsome face.

Although there are many approaches to building, repairing, and maintainng the 1911 pistol...but there are some things that just aren't open to interpretation. Correct headspace...and the methods for verifying the same...
are two of those things. Period.

Cheers all!

 

[1911Tuner]

Tolerances and the Triente y Ocho

Depends on which direction it goes. Deep chamber with no rearward movement on firing...notta biggie. Remember the days when the Super
headspaced on the semi-rim? Accuracy was the main gripe.

If the round backs out of the chamber very far, it could be a real big problem. When the game shooters discovered that they could hot-rod the Super and "Make Major" with a heavy bullet. They also blew up a few guns along the way. Enter the fully ramped barrels...which allowed for reliable feeding without resorting to dicey throating that often had to be done on the Supers.

Headspace gauges are held to pretty close tolerances. Generally plus/minus
a half thousandth...or 8975 to .8985 for the GO...and .9215 to .9225 on the NO GO. It's the chambers that vary. The .45 ACP has an allowable headspace tolerance of .022 inch...which is pretty forgiving...but the maximum is critical. The minimum is less so because very few rounds have cases that get to within the SAAMI maximum of .898 inch. Most fall well below that into the .890 inch category. Some few make maximum though...
and those won't go to battery in a shorter than minimum chamber. Even so,
very few factory chambers are minimum. Most fall somewhere between
.903 and .915 inch...which would allow for even slightly over-maximum length case. The minimum gauge is just a way to try to cover all bases in order to make the gun reliable. Since the original concept was to send the gun to war...lives depended on it. Tight lockup and match-grade accuracy were
far second considerations.

There are several variables inolved in dynamic...or working headspace. The chamber depth relative to the hood face can be perfect. Everything can be within tolerance for good headspace...and all it takes to spoil the show is
for the locking lugs to be mislocated a few thousandths. If you're so inclined,
you can fully fit a barrel...complete with finish reaming the chamber to depth
so as to hold the headspace minimum plus .005 inch...send the top end of the gun to me, and I'll return it with a near certainty of blowing a case head...
or at least bulging them to a frightening degree.

All that's required is to use a square, safe-sided file to set the front faces of the locking lugs back by .020 inch. The headspace will then be .025 inch
above minimum...or .003 beyond allowable. Dangerous...especially if the barrel throat is right on the peg. This is what happened when our friend
cleaned up the damage to the Norinco barrel that got all this started. The
lugs were squared up on the damaged thrust faces, and looked very nice...
but the already loose headspace typical on most Norincos was taken badly out of spec...and had more than .040 inch over mimimum...and about .020 over maximum. A ka-boom was very likely.

Anyway...back to the experiment. On firing, the barrel will be thrust forward away from the slide...the case will back up until it meets the breechface...and the head will be badly unsupported. A kaboom will be likely.
Maybe not today, and maybe not tomorrow...but one day for sure, given enough use, because the lugs will be set back a tiny bit with each pull of the trigger, accelerated by the slop created by filing the lugs back....and it's probably just a matter of a couple thousand rounds.

Standin' by with file in hand...Your call. If you choose to do this experiment
for the sake of science...I strongly advise rigging up a remote firing device for the gun.

 

[BluesBear]

Back to the original question....

What is "Headspace"?

Headspace is one of the most critical (if not THE most critical) measurements in a cartridge fired firearm. The only other measurement that comes close is bore diameter.


On one end of the headspace spectrum are guns that won't chamber ammunition.
On the other end are guns that are shrapnel machines.
I prefer mine to be in the middle where they were designed to be.

If your headspace is excessive, in essence your chamber is only made from ~.010" brass.
Just as a chain is only as strong as it's weakest link, a pressure containment vessle is only as stong as it's weakest area.

And don't ignore that hole in the back. If the head isn't supported by the breechface you have a built in pressure relief valve commonly caller a primer.

 

[Jammer Six]

Ooooooh!

A trigger with holes in it!

How cool! How Tactical!

I have the safety handled, now I need a Tactical Combat Trigger with Holes!

 

[1911Tuner]

Tactical and Cool...and Headspace

Jammer...You simply will not do.

Headspace!

To determine your working headspace, remove the slide...insert a minimum GO gauge under the extractor, and work it into the barrel as you push everything together, pressing the barrel firmly into the slide. Try different
thicknesses of flat, blade-type feeler gauges until you find one that will
fit between the rear of the gauge and the breechface with light drag.
Add the thickness of the feeler gauge to the length of the gauge. Voila!
Static headspace.

Now...to get an idea of how much additional headspace can be obtained with ammunition...pull a bullet from a factory round and do the test over. Voila!
Working headspace...with THAT particular round. Check 10 or 12 to get an idea of what you have within a certain lot. I don't advise doing this particular exercise with live ammunition...If you tickle the primer a bit too hard, you will have a discharge that produces all the velocity and energy of
the round being fired in the normal fashion. Fired brass tends to shorten
a bit upon firing, due to the expansion, and will produce a false reading...but adding a couple thousandths to the measured length will getcha close. Fired, resized brass is better.

SO...it's easy to see that factory brass that is at the minimum spec (.888 inch) can produce a lot of working headspace in even a closely held chamber
of some .900 to .905 inch as measured from breechface to stop shoulder.
This is why there are MINIMUM and MAXIMUM allowable dimensions. A chamber that has been reamed .010 inch too deep, along with a round that is at the minimum length on the case results in .022 inch of working headspace.
Not dangerous...due to being "out" in the safe direction...but still approaching the condition of headspacing on the extractor...just like firing a GAP round in the gun.

New gun that is barely within allowable specs...with only one locking lug
absorbing the recoil forces...and the lug sets back enough to allow the case to have excessive headspace in the UNSAFE direction...and disaster could loom on the horizon with maybe another 5,000 rounds fired, as the lugs continue to wear and set back. The more lug setback there is...the faster
the process goes, due to the slide and barrel having a "running start" at each other when the gun fires....so instead of a gradual shearing force acting on the lugs, you have an impact stress...and so it goes. Equalized lugs will
forestall the process. The stress on each lug is divided. When only one takes it all...even #1 which has the most support...the service life of the barrel is reduced...and possibly the slide as well. This is why a correctly fitted barrel will outlast a sloppily fitted barrel by a considerable margin...
and how many factory guns have well-fited barrels? Damn few.

If you're a moderate to heavy shooter...15,000 rounds a year or more with a factory gun...a headspace gauge set is a worthwhile tool to have. The fingers that you save could be your own. I check my range beaters regularly...and when one closes easily on my homemade .910 "Field" gauge...the gun is either retired from hard duty or rebarreled. No exceptions.

 

[Bill Z]

We weren't taling about losing digits or going .40 over minimum, at least I wasn't. I was asing about the roughly .010 headspace a guage set leaves you with. Like you said, a .45ACP is fine with a max of about .020, which is two football fields and a driving range to me and is totally unacceptable, even for a service grade firearm.

ow, Bluesbear hit the target with thuis statement, we might have a mastersmith in the making.

If your headspace is excessive, in essence your chamber is only made from ~.010" brass.
Just as a chain is only as strong as it's weakest link, a pressure containment vessle is only as stong as it's weakest area.

And don't ignore that hole in the back. If the head isn't supported by the breechface you have a built in pressure relief valve commonly caller a primer.

This will make a huge difference in something like the .38 super, or any high pressure round. "Because of the high pressure in this latter case, the primer sets back and extrudes a little into the firing pin hole. The little piece of extruded primer, extending into the firing pin hole, gets sheared off when the barrel moves down as part of the ejection sequence. This small sheared off piece of extruded primer can cause a number of problems, the most common being that the firing pin motion is impeded and ignition becomes erratic. So, IPSC/USPSA 38 Super shooters do exactly as you do: use a new unfired case as a gauge to produce a chamber with zero head space. When that new case is loaded, the bullet expands the case slightly, which causes the case to shorten slightly, which allows for reliable operation. Subsequently, the case shortens slightly more during each resizing, allowing the rounds to continue chambering reliably, with minimum head space."

Now, we have another whole ball of wax, don't we?
If it's that way for a high pressure round, it certainly won't hurt for a low pressure round.

Cat skinnin', there's more than one correct way to do it, some just are help to higher tolerances than others.

 

[1911Tuner]

Well....

Lemme see...Where do I start?

First...I know that .020 inch of workin' headspace is a bit loose. Never said that it was a good thing. I only went that route to show what could result from tolerances stacking up in the wrong directions.

Second...I wasn't describing the method(s) for hard fitting a match-grade barrel into a match-grade gun...I was offering SAAMI/ordnance specs only. Yes...It's common practice for some smiths to set headspace at bare minimum, or even a tick below...for whatever reason deemed appropriate buy the builder. While I don't want .020 inch of working headspace in anything, safe or not...I'm perfectly happy with .005 inch over miimum. (.903 chamber shoulder to hood face)

Third...We were asked what headspace is, and a good description was given
as well as how to verify the same...and then it went off on a tangent...somehow....again.

Headspace is: The distance from the breechface to the chamber stop shoulder with the gun fully locked in battery. This distance is checked and
verified by the use of SAAMI standard headspace gauges and accurate shims or feeler gauges...OR...in a pinch...by using an empty case of KNOWN length, and the use of feeler gauges to determine the total distance between the shoulder and the breechface. Not the preferred method, but it'll do in a mad rush ONLY when proper gauges aren't available. There is no other way. It can't be verified by eyeballing or guessing at it...and it can't be verified by dropping a gauge or loaded round or empty case into a barrel. A barrel manufacturer can tell me that I don't need to gauge their barrel...but I'll do it anyway because they only have control over the chamber's finished dimension...and that's only half the story.

Question has been answered. Anyone have anything to add?

 

[Bill Z]

Although there are many approaches to building, repairing, and maintainng the 1911 pistol...but there are some things that just aren't open to interpretation. Correct headspace...and the methods for verifying the same...

You brought this up so I had questions on the matter that I thought were worth exploring. The matter is more in depth than just an arsenal check. I was hoping it would lead to the discussion of manufactureres going to the use of a 38 super/ 9mm firing pin to more fully explain the 'phenomenoum of headspace' that it has become. I'm waiting on the call from Niagra's power generating plant about their concern of all the lightbulbs starting to come on and taxing the national power grid. The only thing that is absoloute is that there is no absolute one way of doing things.

I wish I didn't have to go to work, better yet, I wish we could get a chat room going to discuss this deal in real time, but alas, I must leave this good company until the morn. Good evening to all!

 

[jefnvk]

Just a quick addition to the question, I have heard that you can simply use a live round in place of the GO gauge. Is this true?

 

[1911Tuner]

Live Round

'Twas asked:

I have heard that you can simply use a live round in place of the GO gauge. Is this true?
************

Nope. You heard wrong. Cartridge cases can vary in length as much as .010 inch...or more. The SAAMI GO gauge...for the .45 ACP... is standardized at .898 inch long. NO GO is .920 inch.

As noted...In a pinch, you can use a fired case if you measure it and use
feeler gauges between the rim and breechface to determine total working headspace...but that's known as a "Field Expedient" and should only be used
when a gauge isn't on the scene.

 

[Old Fuff]

It is clear that this issue isn’t going to go away …

On one side we have those that claim that headspace in a 1911 pattern pistol can be determined and/or fitted and adjusted using an unfired cartridge case, or a cartridge itself.

On the other those who believe that the only correct way to determine proper headspace is by using industry-standard “go†and “no-go†gauges, with possibly some “in-between†gauges for working purposes.

And at the end of the arguments the real core question remains – “who are you going to believe?â€

The Internet is filled with advisors on any subject you can imagine. The problem is that usually the advise will come from someone you don’t know, and who’s qualifications are a mystery. Any adviser may claim all kinds of expertise and experience. But how do you confirm the truth, given that some have more mouth then brains, and sometimes the worst sound the most plausible. So unless you’re getting the word from someone with an unchallengeable and unquestionable reputation, there is always some element of doubt.

As I traveled to the SHOT Show late last month I thought about this, and the issues surrounding headspace and the 1911 pistol. Then I decided to see if I could find a way to resolve the matter. I would have an unique opportunity, as a substantial number of truly qualified people would be there from all over the country, and with my press credentials I would be able to walk through doors and talk to various individuals that otherwise might not be accessible.

So when not attending to other duties I discussed the headspace matter with about a half-dozen people, ranging from the president of a small company that manufacturers this kind of arm, to the individual that I’m about to bring up.

Dave Bennetts works for Brownells in Montezuma, Iowa. As they are the largest purveyor of gunsmithing tools, supplies, parts, and endless miscellaneous related items, in the world I suspect they need no further introduction here. Their creed is “Selection, Service, Satisfaction†and they live up to it every day. Throughout this forum I have seen uncounted posts referring to Brownells for one reason or another, and I have never noticed a negative one.

Mr. Bennetts title is “Tech Support Gunsmith.†Part of his responsibilities is to answer telephone or e-mail requests for advice or information. The callers range from all levels, from big-name professional gunsmiths to pure amateurs with little or no experience. All are treated with the respect they deserve, and it goes without saying that the guidance that’s offered is backed by Brownells own impeccable reputation.

I should mention that The High Road was unknown to him. He is not a member, has never lurked, and has no known connection with anyone here. Thus he has no preconceived notion concerning the past discussions that have gone on here or the people involved.

At the time I spoke to Dave the Brownells booth was crammed with visitors, and he was up to his eyeballs with folks seeking to get his attention. Never the less he took the time to explain the ins and outs concerning headspacing, what worked, what didn’t and why. He quickly and easily reduced the more complicated technical parts to common English.

At the end of our discussion he made a generous offer. He said that if anyone on this forum, be it some of the staff, or a moderator, member, or even a lurker wanted his views or advise they could simply call or e-mail and he would answer any questions they might have. The necessary contact information is listed at the bottom of this post.

I am well aware that some are so fixed in their opinions that even Mr. Bennetts' position won’t sway them. But I believe that Brownells’ reputation for excellence will be good enough for most of you that may inquire. I am well satisfied with what he told me, and I believe that if you talk to him you will feel the same way.

Dave Bennetts – Technical Support Gunsmith
Brownells, Inc.
(800) 741-0015
[email protected]

 

[P95Carry]

Useful post Fuff. Have to say, very often with some things we read, there can be a ''that makes sense'' element within - often is ... sometimes not.

I may be advantaged thru my engineering background... but usually only accept what is made understandable and logical.

 

[Old Fuff]

P95Carry:

I agree, but some can make the illogical sound logical …

If that wasn’t true a lot of senators and representatives couldn’t get re-elected …

 

[Dean Taylor]

Old Fuff,

I did not know you were going to the Shot Show. I would have liked to have met you. I would have liked to buy you lunch (or dinner) like I posted to Tuner.

I also discussed the .45ACP headspace topic with multiple individuals including an individual at the Brownells booth, several different manufacturers represenatives, and multiple pistolsmiths at the Shot Show. I have not posted the results of my extensive survey effort as I do not like to post anything where an indivual is banned from commenting when things are directed at that individual.

Did you see my Custom Caspian ShortSword01 at the Caspian booth? .45ACP Ed Brown barrel.

Dean
[email protected]
410-952-7848

 

[Old Fuff]

Dean Taylor:

While I was at the SHOT Show, I was also there on assignment and therefore my time was tightly scheduled. Consequently I probably couldn't have met you for lunch, because in my case meals were also assigned for purposes of getting interviews.

I agree that one should not post someone elses views without giving that person an opportunity to comment. Also of course anyone who might be the object of those views or comments. Consequently I carefully avoided identifying the people I spoke to except Mr. Bennetts. I had his express permission to reveal his identity, phone number and e-mail address. However anyone who wants to know his feeling on the issues will have to get them directly from Dave. That said, no names of any individuals came up in our conversation so I am sure that whatever Mr. Bennetts may have to say it will be directed expressly toward the issue and not any particular person.

Unfortunately I didn't get to see your Caspian Short Sword # 01. Because of the size of the show (over 1730 exhibitors) and the fact that other duties kept me off of the floor some of the time, precluded me from seeing everything that I wished I might have. Since my return I have been informed by several parties that I missed something that I shouldn't have.

 

[1911Tuner]

Fuff at the SHOT

That's the thing about the Old Fuff...He's like a double-naught spy...incognito. You mighta even met him without knowin' that was who you were shakin' hands with.
It coulda been one of those: "OMG! What an honor to meet you sir!" moments...and you'd never know, 'cause he'd shake your hand and tell ya the he was glad to see ya there amongst all those fine folks at SHOT.

And so...we keep tryin' to figger out: "Just who IS that masked man?" Who knows? Maybe de Shadow do...

I can't tell. He said he'd hafta come kill me if I did...

 

[Bill Z]

So unless you’re getting the word from someone with an unchallengeable and unquestionable reputation, there is always some element of doubt.

You are right on the money Fuff, you hit the bullseye, and couldn't get closer.

Part of the comment I posted above was from someone that I would be certain that you would respect as one of those people with an unquestionable reputation. Here is the entire text of the reply that I got in an e-mail from this gentleman. This wasn't about the barrels he produces, this was about fitting, headspacing in particular.

Hello Bill,

The use of head space gauges usually produces roughly 0.010 of head space. This allows the primer to set back when the cartridge is fired. This isn't much of a problem with a 45 ACP. It is a large problem with the high pressure 38 Super loads common in IPSC/USPSA shooting. Because of the high pressure in this latter case, the primer sets back and extrudes a little into the firing pin hole. The little piece of extruded primer, extending into the firing pin hole, gets sheared off when the barrel moves down as part of the ejection sequence. This small sheared off piece of extruded primer can cause a number of problems, the most common being that the firing pin motion is impeded and ignition becomes erratic. So, IPSC/USPSA 38 Super shooters do exactly as you do: use a new unfired case as a gauge to produce a chamber with zero head space. When that new case is loaded, the bullet expands the case slightly, which causes the case to shorten slightly, which allows for reliable operation. Subsequently, the case shortens slightly more during each resizing, allowing the rounds to continue chambering reliably, with minimum head space.

The shooting community roughly gravitates into two groups, one of which is, more or less, superstitious, and the other is, more or less, scientific. You belong in the latter group. You are reading reports coming from the other group.

Hang in there. Your brain is working just fine.


Now, I will forward the original e-mail to Tuner or to Fuff so you can verify who this was under the agreement of confidentiality. I am sure you will vouch for this mans integrity, experience, and expertise in the matter, whether you agree with him or not.

Now, in speaking to many people in the industry at Shot, I did pose this question to a few of them. These were manufacturuers and smiths alike. The main conclusion that they came to went about like this.

The go/no-go guages were absoloutly indespensable on their production lines as one of the final checks. They were concerned that the barrels were within spec. The custom shops and smith's however used new cases to get a closer tolerance, and this was the preffered method for a fitted barrel.
The go/no-go guages were indespensable at an armory, military or otherwise as these firearms typically had to be safety checked en'masse' so the troopies could use them for training or duty. It was also the most expedient way to check the rebarrel of a firearm as drop-ins are the norm and used wasn't unusual.
The go/no-go guages were unheard of being used by the GP at gunshows, but wouldn't be a bad idea, just highly unusual.
Fitted barrels were alomost always checked against new cases for a perfect fit.
At the end of the day, when the consumer picks up his new pistol, whether it be from a fellow like me, or a retailer, or a private sale, he's going to grab a box of Whincheter whitebox/Golden Sabre/Corbon Powerball/S&B whatever and load them up in his Chip/Wilson/Tripp/47DPower mag, insert it and go shooting. Now, how many of you go around case guaging all of the new ammo you buy?


BTW, I have spoken to dave at Brownell's several times on the phone, about anything from night sights to bolt carriers to magazines and tools. He is a very nice fellow and a jack of all trades. I didn't know he made Shot, but my business at Brownells was with Jeannine, and like everyone else with appointments, we were pressed for time.

 

[Bill Z]

It coulda been one of those: "OMG! What an honor to meet you sir!" moments...and you'd never know, 'cause he'd shake your hand and tell ya the he was glad to see ya there amongst all those fine folks at SHOT.

You think? I met everyone that I really wanted to meet that would impress me in the business, including the press people.(You see, we too had a press pass) Could he be Roy Huntington, John Taffin, Jim Scoutten, Ichiro Nagata, hmmm.
Was that you we ate dinner with at the Sahara, or breakfast with at McDonalds Fuff? Geeze, if we would have known that we would have bought.

Now, since it did stray, the topic I mean, and I didn't steer it down this road, I did meet some really neat people while I was there. Ken aka Wildalaske from here was one of the most colorful people I met there, he's in real life like he is here on the boards, really enjoyed the chat we had. Roscoe Benson, from 1911 forums, had some neat stories to tell and info to pass along. Heck, Sunday we should have just hung around the whole day, we kept popping up at the same places.
Besodes meeting all of our suppliers and the great group of guys over at Louder than Words, one of the neatest people I met was Bob Marvel. The man is dedicated to the perfection of his work, and the examples of the work he had on display at the Caspian booth was incredible.Be on the lookout for a new .22 conversion and another nice jig.

Since you did miss the Caspian booth Fuff, you missed acouple of nice pistols by Terry Tussy, including a tiny little concealable 1911, about the size of a Colt pony, Dick Hienie had a great 9mm there. Bruce Piatt spent a couple of three days there and Matt Mc
learn had one of the nicest open guns I've seen. It was kind of like the place all the cool kids were hanging out at. It's worth a look next time your there.

Oh well, I rambled on, someone's rubbing off on me.

 

[Old Fuff]

Bill Z:

>> The shooting community roughly gravitates into two groups, one of which is, more or less, superstitious, and the other is, more or less, scientific. You belong in the latter group. You are reading reports coming from the other group. <<

So if I understand correctly, those that determine headspace by using an unfired cartridge case are "scientific" in their approach, while those who use precise gauges are "superstitious?"

Perhaps your source might enlighten the voodoo folks about what particular make and lot number the “headspace case†should be drawn from. I suppose thereafter it would be advisable to use only those particular cartridge cases.

While Tuner has address this issue from the point of view of commonly owned .45 pistols, you seem to be focused on exotic game-guns that are custom made for the express purposes of firing loads which exceed all recognized industry standards for the round you mentioned. In fact, I can remember when these pistols were the rage among some gamers, magazines such as “American Handgunner†refused to print the specifics of some of the powder charges that were being employed because they were so excessive.

The only way you can have true zero-headspace in a firearm is to either use a case that has been fire-formed in a particular (bottlenecked) chamber, or have a chamber made slightly short for a (straight) case and then trim each case to length.

We have already had a situation involving a Chinese-made pistol where the headspace was supposedly correct when it was checked using the “scientific†/ cartridge-in-the-chamber method to ascertain the headspace was O.K. that later has repeatedly failed to pass the test when a “superstitious†no-go gauge was used. Fortunately the true condition was discovered before any damage was done to the pistol, or a user was injured.

In closing I would point out that if the chamber is long enough – or for that matter too long – you can place an unfired case or loaded cartridge into that chamber and the gun will close and go into battery – regardless of what its headspace really is. If someone who is inexperienced tries to check the headspace of THEIR pistol using nothing but a new, unfired case or a randomly selected cartridge they will learn exactly nothing of value. And if, as was true in the above-cited instance, the headspace is really excessive someone might get hurt.

Now forget about gamer-guns and think about those consequences.

 

[Bill Z]

It's not just about gamer guns. The above would be true about all 1911's. If it works for high pressure rounds it would work for low pressure rounds. The guages leave more of a headspace than an unfired case.

This is an e-mail from a top manufacturer, you have an offer on the table, I'm just not going to drag this out because of this verocious attempt to try to drag people in the mud that don't agree with your viewpoint. I've not been condecending to anyone, mearly pointing out different sides of a coin. I have not been afforded the same courtesy here. Like I said, this fellow, a specialist in his field, who knows more about this than a general smith, answered this question. As you notice, he didn't degrade either method, but he pointed out some facts. Are you saying that the 38 Super is just for gamers? Remeber when it was what the FBI/Treasury carried?

Once again, you may not agree with this fellow, obviously you don't but I'm certain you would would have to admit he falls better into your criteria than any general smith.

(BTW, it's no one that really knows me from Adam's housecat, I've only installed one of his barrels and it was supplied by the customer, so I don't have any business dealing with them to this point.)

BTW, how many headspace guages has anyone fired out of their pistol? Remember, it's ammo you shoot out of them, and no one has said if they case check all of their new ammo. If you are that concerned about tolerances of new ammo, why isn't this a big priority?

 

[1911Tuner]

And they're OFF!

Have I missed somethin' here. Howdahell did we go from a discussion on
verifying safe headspace in general-purpose, ordnance-spec production guns to arguing the methods for hard-fitting a barrel into a special-purpose game gun that is meant to fire hand-tailored ammunition loaded to near proof levels? Bill...Are you tryin' to confuse the issue?

We've fought over the Custom Bling Thing vs the Warhorse issue...comparing if you like, a Ford pickup truck to a Coupe de Ville.
I guess now we'll have to argue about the Truck vs a Lambourghini Countach. We're still Apples and Oranges, no matter which fruit stand
we're in.

Okay...We'll talk about the IPSC .38 Super "Cheater Guns" if you want to,
but first...my standard disclaimer...for about the 353rd time.

I don't build custom guns. Can do, but don't.

I don't build comp guns. Not interested.

I don't build raceguns. They're wonderful toys, but for my purposes, you couldn't throw one at me.

I don't build very many match-grade pistols. I do dabble with rifles a bit, but that's another forum.

And I sure don't have any interest in building or owning anything that
is headspaced so that it requires carefully controlled length of the brass or
that once required the use of small rifle primers to keep from blowing one out.
Maybe they still do...I know that once upon a time, I couldn't find a brick of small rifle primers because these gamers were buyin'em up as fast as the dealers got'em in. I also heard about a lotta blown guns in those days...even WITH the ramped barrels that they ushered in.

A builder/purveyor may use anything that he wishes to set the chamber length from breechface to shoulder...as long or as short as he deems acceptable. I occasionally use a .895 gauge to set that dimension
in a .45 ACP pistol...for a variety of reasons, depending on what I run into
on the lugs, and whether they're bearing the thrust load evenly.

But I digress...I can use a length of .885 inch, and hold that to within a
,001 inch tolerance if I'm very careful. Not a problem if I trim the brass that is to be used in the gun to just below that length. On the other hand, if I
go into any given gun shop or Wally World and buy a box of off-the-shelf
ammo...I might just have a big problem in getting the gun to chamber the rounds and fire. Not a problem if the chamber dimensions are within
SAAMI standard specs for the caliber. Go buy any old decent brand of ammo, and the gun will very likely work...and .010 inch of working headspace won't mean a thing. When the pressure levels go off the scale
for the SAAMI limits for the caliber...and .010 inch could blow something up.

When you next talk to the scientific gentleman, ask him a simple question for me. Would it be more precise to use a randomly-selected case with which to set his headspace at X dimension...or would it make more sense to simply make a gauge to that predetermined dimension so that all chambers would be the same...gun after gun? Sorry...but grabbing a
new brass case and using it to set a critical dimension on what is supposerd to be a precisely-built gun seems to me a bit haphazard...

One final point. The comments:

>The go/no-go guages were indespensable at an armory, military or otherwise...<

Exactly what the argument started over in the first place. The gauges are used to verify safe headspace so that the gun can be either accepted or rejected for issue...and that was my only point.
*******************

And:
> safety checked en'masse' so the troopies could use them for training or duty.<

Not tryin' to pick a fight...but that touched a hot button with me and probably several other active and inactive military people here, even though
I'm sure that you meant no disrespect...but these "Troopies" have
offered up their lives...bled, suffered and died so that you could call them what you will, and would do so again any time, anywhere at the drop of a hat...but I feel that they'd appreciate it if you'd come up with a term that all of them have earned and richly deserve.

Soldiers...Sailors...Airmen...Marines...or just plain "Troops" works well...but
please, Almighty God, don't call them...us..."Troopies." We've bled too damn much for too long to earn something a little more fitting of our sacrifices.

Now...back to the original topic...which had nothing to do with hard-fitting
a special purpose gun with a limited application...and no...it doesn't have anything to do with the FBI or whoever who issued the Super for a time. They didn't carry the ported, compensated game guns, nor were they issued ammunition that approached rifle pressures. The whole question was...and is...What method is the industry standard for verifying safe and serviceable headspace in a service-grade weapon? Hint: It ain't droppin' a randomly-selected live round into a chamber and callin' it good just because it sits flush with the chamber hood. If you want to discuss hard-fitting a barrel in a match-grade or limited application-arm...we can do that. There are several methods...and everyone has thier own technique. Start a thread on it. Ah'm ya Huckleberry...

 

[Bill Z]

Tuner, I too was military, so was my Dad, 28 year veteran of three wars, ret CSM, deceased. The term Troopies is not an insult, it's one he used, quit making a mountian out of a molehill, even if your good at it. BTW, the 38 Super was an issued caliber and in some parts of the world still is. I personally never mentioned a comp gun or game gun, did I?

I guess my offer will not be taken up on, hopefully the one's you suggest that endanger peoples lives and limbs won't be either. At least my offer was one that wouldn't get anyone hurt, read: much more responsible than your suggestion for someone to blow up a gun. I have sought professional opininions of people with actual experience. Of course, they must not be as experienced as you or live in the 1911 hotbed of the US. None of them, after making their sole living at it for 12 to 20 years have ever seen 72 Norinco's or 100 Springfileds for armory checks and are quite amazed at your numbers, especially for one years or less work by a non professional not making their living at it. (Was amazed the word used?) Why you cannot admit that there is more than one way to do this is beyond me. My question still hangs out, do you caseguage all new ammo? Why not if the answer is no?

 

[1911Tuner]

Mountains

Okay Bill...didn't know you were ex-military, so you get a free pass on the troopie thing. it's like somebody callin' a marine a "Jarhead" having never
paid homage to Iron Mike. No harm, no foul...

As for the comp gun/racegun issue...you brought it into the argument a few posts ago...where the builder stated that using a new case to set headspace was his method. I've already aquiesced that that can be done...but that wasn't the original question, nor was it the topic of discussion. The question was: "What is Headspace?" The questions were(mainly) How does one
verify correct headspace. Not..."How do you set up a racegun/match gun/comp gun/ etc. The question was answered, and correctly so...until it went into overtime comparing the methods of custom pistolsmiths when hard-fitting a barrel into a hand-fitted gun.

Headspace is: The static distance between the breechface/boltface with the weapon locked fully into battery. Very simple.

The answer to the secondary question as to how to accurately measure headspace is:

By measuring it with known, standardized devices known as Headspace Gauges...the dimensions of which were long ago set by the SAAMI. This
has no bearing on actual working headspace because factory ammunition case lengths vary from lot to lot and from round to round within the same lot.
The only way to insure the same headspacing with each round fired is to
trim all brass to the same length...and even that will have a plus/minus tolerance. No such thing as a perfect dimension, I'm afraid. Any engineers following this thread are welcome to comment...Please!

These dimensions pertain to standard-spec chambers...caliber specific. They don't cover an enterprising individual's "improvements" or interpretations.
We can turn Grandma's station wagon into something very different than what
the Society of Automotive Engineers had in mind for Grandma...and the same goes for Grandpa's old pistol that he carried into the interior of Guadalcanal...
but that doesn't mean that it's standard OR better. it just means that it's possible.

As for the Molehill/Mountain comment...I didn't start this fight, and I didn't provide what could POSSIBLY be a dangerous method for verifying headspace.
I only corrected what could POSSIBLY have turned into a disaster had somebody who is inexperienced used that method, believing that all was well, when it in fact MIGHT NOT have been.

Why don't I gauge every factory round? Because good quality, modern ammunition is made to certain specifications and tolerances, engineered to work in standardized chambers under less than ideal conditions. While anything can go wrong during mass-production, it's rare for metallic cartridges to get to the shelves in an out-of-spec condition...and has been for over a century. Now, if we're gonna go back to discussing tighter than SAAMI-spec chambers in guns that were never meant to see real service, all bets are off. Ordnance specifications...Concentrate on that term. That's what I adhere to, and only deviate when the gun is to be used strictly as a toy...and I don't do very many toys...but, please do carry on.

 

[ken grant]

Headspace

Old DumbA** me don't know a whole lot about Gunsmithing but I have fooled with guns all my life and have read many books( even stayed at a Holiday Inn express)
I have had several friends who were gunsmiths and did all sorts of re-barreling and I have spent many hrs. in their shops.
Now in my humble opinion trying to set headspace in a 1911 with out the slide would be like trying to headspace a rifle with no bolt!

 

[BluesBear]

back up the bus.

Because of the high pressure in this latter case, the primer sets back and extrudes a little into the firing pin hole.

Primer cups are made of metal.
They ain't made from paper mache, Play-Doh, Peruvian Yak toenails or recycled Glock frames/K-mart shopping bags.

They're made from metal. Metal of a certain thickness.

And yes in high pressure cartridges the primer often backs out of the case a wee bit until recoil reseats it. That's how primers end up flattened and flush with the case head. That's no big deal almost every .38 Special +P does it.

But...

If you have a primer extruding INTO the firing pin hole, YOU HAVE A PROBLEM.

Either you are way over pressure,

or

you have an improperly fitted firing pin.


Don't try to tell me that primer flow is normal.


I started handloading .38 Super in 1977.
I personally have loaded .38 Super hot enough to bulge the case bases into the feed ramp.
I then resorted to cut down commercial .223 brass and loaded them even hotter.
But even then I NEVER had the primers extrude into the firing pin hole.
And I never pierced one. (CCI #500 small pistol primers exclusively.)


Perhaps that is because back in the 1950s Colt new how to properly machine a slide and fit a firing pin?