Measuring Shoulder Setback?

[something vague]

I have just recently picked up a Sinclair bump gauge and am having some little issues. It is for the .223 Rem out of a bolt action.

On measuring some fired cases that I have loaded once I can see no difference in value from before I loaded them. These are brand new Hornady Cases that I went through fire forming. This is also true with some Factory Loaded 55gr Hornady V-Max bullets. The fired case gives me the same measurement as the loaded round.

The only place I get a different measurement is from some factory Remington 55gr PSP. The loaded round measures out to be smaller than all of the rest of the cases that I've measured (including Hornady's loaded round) and the fired case gives me the same measurement as all of the rest of my fired/unfired cases and Hornady's factory V-max bullets.

Could it be that all the non fired and Hornady loaded rounds have measurement that close to my chamber shoulder dimension? I bought Sinclair bump gauge insert #23 (which seems kinda big), is this the right insert for .223 Rem? It says it's for the .223 family but doesn't list .223Rem. I'm just kinda confused, I assumed that I would always see that my case shoulder would always be larger after firing and would have to adjust my new body die to set the shoulder back at least .001".

 

[243winxb]

I assumed that I would always see that my case shoulder would always be larger after firing

A flrs round can be shorter after firing, when the body of the case has room to expand in the chamber. Also measure the body right behind the shoulder, before firing, and after. Mine has .005" difference, they get shorter.

 

[Walkalong]

It's unusual to see no difference in a fully sized (shell holder against the ram) case, and then that same case fired in your rifle. Maybe you are not fully sizing your cases.

Maybe you do have a short chamber. That is not a bad thing, as long as rounds fit.

I would check and recheck my measurements though. If your measurements are good, you should get very good case life.

A flrs round can be shorter after firing, when the body of the case has room to expand in the chamber.

Yes. Case length will shorten, but he is asking about the shoulder not being any farther forward after firing. Usually it is, despite the overall shortening of the case.

 

[MCMXI]

something vague, if you neck-size only, it may take three, four or five firings of a case before the shoulder stops moving forward. This is what I've experienced with my four bolt action rifles. I use Redding Instant Indicator Case Comparators for all of my rifle calibers. Cases fired in my DPMS (24" stainless heavy fluted barrel) upper are SAAMI + 0.001" so factory brass sized to SAAMI specs really doesn't have much room at all. I neck-size and then use a body die to bump the shoulder back to SAAMI - 0.002" for all cases that I use in that rifle. I've shot hundreds of rounds resized in this manner with zero problems.

 

[243winxb]

Head to Shoulder Measurement.

Quote:
I assumed that I would always see that my case SHOULDER would always be larger after firing
A flrs round can be shorter after firing, when the body of the case has room to expand in the chamber. Also measure the body right behind the shoulder, before firing, and after. Mine has .005" difference, they get shorter.

Yes. Case length will shorten, but he is asking about the shoulder not being any farther forward after firing. Usually it is, despite the overall shortening of the case.

I am talking shoulder, not case length.

the shoulder not being any farther forward after firing.

He got lucky, the flrs die/factory ammo and chamber match.

The only place I get a different measurement is from some factory Remington 55gr PSP.

And they got bigger after firing? Same measurement as the others? Then the body could not expand and the shoulder was pushed forward. My guess a tight chamber would do that. Same as when only neck sizing, the brass has no place to go but forward.

 

[Walkalong]

I am talking shoulder, not case length.

OK, but the shoulder moves forward upon firing, not back, despite the case expanding to fill the chamber. This is, of course, assuming the cases shoulder is not up against the shoulder area of the chamber already, which is not usually the situation when full length sized cases are put in a standard chamber.

 

[243winxb]

but the shoulder moves forward upon firing, not back

I have seen/measured the shoulder moving back on M16A1 5.56mm fired brass. Using a max. loading of 21.0gr IMr 4198 w/55gr win. fmjbt. The body expands .005" right behind the shoulder.

 

[243winxb]

The bolt slamming an empty sized case that has a longer head to shoulder measurement then the chamber can get a .002" shoulder setback. The firing pin can set the shoulder back also. Bart B. said >

I used to think this was normal. Then I measured shoulder setback firing empty primed .308 Win. cases in several rifles chambered for them. Neck only sized and fired reprimed cases had their shoulders set back the same amount as full length sized cases with shoulders set back a couple thousandths when sized. Shoulder setback caused by firing pin impact was about 8 to 10 thousandths of an inch with all of them.

Every rimless bottleneck fired case I've measured has always been shorter than before it was fired. It's the sizing process that makes them longer. How much is determined by the dimensions of the fired case and sizing die.

http://www.thehighroad.org/showpost.php?p=5625956&postcount=11

 

[Walkalong]

It isn't the norm in generous factory chambers.....

 

[243winxb]

It is for the .223 Rem out of a bolt action.

Simply throw the gauge away. Put a .005" spacer between your shell holder & FLRS die when setting it up. Put a hole in the shim for the decapper pin. The sized case should fit snug with a little extra pressure on the bolt handle. If the sized brass will not chamber , get rid of the shim, your good to go.

 

[something vague]

I'm starting to wonder if my guage is the correct one. It's a sinclair that has the angle of the shoulder machined into it and is #23. When I use the guage I can no longer see any part of the shoulder as the guage sits down at the line where the body and shoulder meet. But then again, my Remington factory loaded cases showed that the shoulder was set back further than what my flrs die does and Hornady factory rounds. I'll call Sinclair just to be sure on Monday.

Ever since I bought this rifle, Ruger M77 Varmint, I have noticed some things about the chamber being fairly small. I have to be extremely picky about what kind of factory ammo I feed it as the throat length is extremely short. A lot of 55gr FMJ ammo ends up with the bullet jamming into the rifling. My COALs have to be fairly short to stay off the rifling around .010", especially compared to other factory chambers.

I just picked up a Redding body die to use in conjunction with my Lee Collet die. I will start off by not touching the shoulder and see how they chamber, and will go from there.

 

[Walkalong]

Simply throw the gauge away. Put a .005" spacer between your shell holder & FLRS die when setting it up. Put a hole in the shim for the decapper pin. The sized case should fit snug with a little extra pressure on the bolt handle. If the sized brass will not chamber , get rid of the shim, your good to go.

Yep...

 

[Bart B.]

Walkalong's comment about my statement that rimless bottleneck cases have their shoulder set back by firing pin smacking:

It isn't the norm in generous factory chambers.....

Well, I'm not agreeing with. All the factory chambers I've checked (.243 Win., 7x57 Mauser, .270 Win., .30-06, .308 Win., 8x57 Mauser, 7.65 Argentine, plus 7.62 NATO and .30-06 chambers in Garands) have had the same thing happen.

The exceptions for rimless bottleneck cases I've seen is when the chamber has excessive headspace on a case too short to safely be fired in it, the extractor holds the case rim back enough that the shoulder doesn't get slammed into the chamber shoulder.

Walkalong's remarks about shoulder's moving:

OK, but the shoulder moves forward upon firing, not back, despite the case expanding to fill the chamber.

Again, I disagree.

The shoulder on rimless bottleneck cases is slammed hard into the chamber shoulder by the firing pin. As the primer's detonation starts the powder burning, pressure builds up. The part of the case that's the thinnest starts pressing hard against the chamber. That part is the neck, shoulder and body right behind the shoulder. As those case surfaces press hard against the chamber walls, they stay there. The back part of the body doesn't' press as hard because it's thicker, so it starts to stretch back. When it's stretched back far enough, the case head stops against the bolt face.

It's this stretching backwards that last effects the thickest part of the case just in front of the extractor rim; it's called the pressure ring. Even though that's the thickest part of the case, it's the last part to get stretched and pressure's highest when that happens. This is why that part stretches too much sometimes, thins too much and finally cracks or comes apart causing head separation.

But a new case shoulder on a belted or rimmed case will blow forward when it's fired. These cases are held back by what they're headspaced on; a belt or a rim. Both are slammed against their respective chamber shoulders at the back end of the chamber.

Learning about this is easy by doing some tests with empty primed cases and reduced loads then working to max loads.

 

[243winxb]

Centering the Bullet in the Center of the Chamber.

the throat length is extremely short

This is good. Seating the bullet into the rifling will center the round in the chamber.

a Redding body die to use in conjunction with my Lee Collet die.

Sizing half of the neck works well for me in 243, even better if neck turning. The unsized part of the neck will expand to the factory chamber, centering the round.This can take 2 or 3 firings. Then on firing the case shoulder can do whatever it wants. I have No personal experence with the collet die, but have read half the neck can be sized with it. I use bushing dies in 243. Problems with the 223 might be the short neck @ .203" and the neck diameter of the loaded rounds. In the 223/5.56 there seems to be a very wide range of chambers and brass neck wall thickness.

 

[Walkalong]

I can only attest to the couple chambers/brass I have measured, such as my .222 Mag bolt gun, & my .223 auto. The shoulders go forward on both of them. I push them back just a bit in the .222 mag, and a little more in the .223.


Bart B. obviously has done a lot more with rifles than I have, (a lot more) so I listen when he posts. 243winxb likes to link and quote a lot of stuff, so I take that all with a grain of salt.

I'll bow out here. Folks will just have to do their own measurements. Perhaps I am all wet on this one. I would love to hear from some others besides folks who seem to have a bone to pick with me.

 

[243winxb]

The only place I get a different measurement is from some factory Remington 55gr PSP.

And they got bigger after firing? Same measurement as the others? Then the case body could not expand in the chamber and the shoulder was pushed forward. My guess a tight chamber would do that. Same as when only neck sizing, the brass has no place to go but forward.

if you neck-size only, it may take three, four or five firings of a case before the shoulder stops moving forward.

Very true, i learned this at a very early age using a Lee Hammer Loader that only neck sized 30-06. Soon or later the rounds will no longer chamber. I have only measured the shoulder on 1 gun, the head to shoulder measurement got smaller with a max. load was a very big suprise to me. But with a larger chamber and the case body expanding behind the shoulder .005" ,i can only guess thats why it got shorter.

 

[something vague]

And they got bigger after firing? Same measurement as the others? Then the case body could not expand in the chamber and the shoulder was pushed forward. My guess a tight chamber would do that. Same as when only neck sizing, the brass has no place to go but forward.

Yes the fired cases shoulder's moved forward. I don't have the exact measurement of how much but the fired measurement ended up being exactly what all the other cases have measured. This includes Hornady's factory loaded rounds, which must mean that my chamber is very tight. I would assume that factory rounds would be sized to fit the majority of factory chambers.

Checking shoulder setback is somewhat new to me so all the insight I can get is great. Thanks for the replies.

Upon firing, whether the shoulder moves forward or if the case head moves backward at the pressure ring point, wouldn't the measurement I'm taking always show the same result? In both instances the shoulder should be farther forward when measured from the case head, right? Therefore in both cases the shoulder would need to be set back after a few firings.

Put a .005" spacer between your shell holder & FLRS die when setting it up. Put a hole in the shim for the decapper pin.

Couldn't I accomplish the same thing by putting a feeler guage of .005 between the shell holder and the bottom of the die and tighten the lock ring?

 

[243winxb]

Couldn't I accomplish the same thing by putting a feeler guage of .005 between the shell holder and the bottom of the die and tighten the lock ring?

Yes, but the die may not be square to the shell holder. The shim will make contact fully with the die and shell holder, not just on one side. You lock the die in while the 2 are still in contact. The squaring of the die comes from an old RCBS news letter.

Upon firing, whether the shoulder moves forward or if the case head moves backward at the pressure ring point, wouldn't the measurement I'm taking always show the same result? In both instances the shoulder should be farther forward when measured from the case head, right? Therefore in both cases the shoulder would need to be set back after a few firings.

Best ask Bart B.

 

[243winxb]

Partial neck sizing with collet die

If you want to resize just a part of the neck, find a washer at your local hardware store the has an inner diameter large enough to fit over the case, and an outer diameter large enough so that it contact the collet sleeve that protrudes from the bottom of the die. Slide this washer over the case after the case has been inserted into the shell plate. Now when the ram is raised, you can still close the collet by applying force at the top of the stroke, but the case will not go up as far into the collet, and the neck will be sized less an amount equal to the thickness of the washer.

From the link below at Lees website.

 

[something vague]

Wow, thanks man. I honestly have never thought about using fender washers as spacers for any of my dies as I was just in the mind set that I could use feeler guages to set the die back the same amount. The die being square never crossed my mind, but now makes a lot of sense.

Do you really think that there is an advantage to partial neck sizing? Have you compared results side by side with standard neck sized cases? And last one, what kind of gun are you shooting these cases out of? Is it a factory rifle?

 

[243winxb]

Your results May Vary-All Guns are Different

Do you really think that there is an advantage to partial neck sizing?

Yes, using a bushing die has improved accuracy. I know partial sizing makes a difference. The more unsized neck area the better, to about 1/2 of it with the 243 win.

Have you compared results side by side with standard neck sized cases?

I tested using RCBS standard FLRS die, compared to there neck sizing die. FLRS was more accurate. The Redding FLRS Type-S bushing die is more accurate than the RCBS FLRS standard die.Using the bushing die, i tested sizing all most 100% of the neck, compared to about 50% . The ammo with the largest unsized neck area was the most accurate after the neck expanded to the rifles chamber, about 2 or 3 firings.

what kind of gun are you shooting these cases out of? Is it a factory rifle?

Factory Remington 40X rifle & Remington Model 600 Mohawk, both in 243 win. Very old like me. The 40X gets neck turned brass with bench rest preparation , no expander. The 600 unturned brass using the expander button. Both showed improvements with the bushing die & partial neck sizing.

 

[Bart B.]

This thread's got much interest from me. I've gone through all these sizing and measuring things myself. It all happened many years ago. Then someone who's probably loaded more types and calibers of cartridges getting probably the smallest groups ever (several 10-shot ones in a row) in rail guns (barreled action clamped in a metal block whose three V blocks were riding on three rods (3-point suspension; most repeatable of any mechanical system) showed me some realities of reloading fired cases.

First, proper full length sized cases gave the best accuracy. But only when the bolt didn't bind or close one bit hard on the chambered round. Any type of neck sizing (partial or complete, nothing on the shoulder or body), or partial full length sizing (full length sizing die used where only part of the neck was sized as well as the body diameters got reduced a bit) never produced consistant, exellent accuracy.

He never worked up a new load when changing powder, primer or bullet lots. Same thing when a new barrel was used; no load work up. Barrels were chambered with standard SAAMI minimum dimension reamers with standard neck, throad and leade diameters. Powder charges were metered, not weighed. Everything shot great all the time. No fancy case prep either; no neck turning, flash hole deburring/uniforming nor sorting cases by weight. The best match bullets in calibers from 22 up through 30 shot 1/4 MOA groups or better at 200 yards.

He used standard RCBS or Redding full length sizing dies with their necks lapped out to a couple thousandths smaller than a loaded round's neck diameter. Fired cases full length sized such that the shoulder was set back no more than a couple thousandths from its fired position. Nowadays, the Redding "S" Full Bushing Die with a bushing of the correct diameter is the same thing.

The people who took over his job still do the same thing the same way. Sierra Bullets' still bases their reloading processes and techniques on this man's success. He was Sierra's head ballistic tech for 35 years starting in the early 50's until he retired in the late 1980's. I recently contacted Sierra to see if they were still doing things the same old way; they responded saying it's still the same old way but they use Redding "S" Full Bushing dies when available; Redding standard full length sizing dies otherwise.

I've always got the best accuracy sizing fired cases this way. If one understands the real differences on how a rimless bottleneck case fits the chamber when it's fired, either full length, partial neck or neck only sized, the difference is microscopic. And full length sized may well align their front end better on the chamber axis when fired than any neck sized one does. None of them have their long axis dead on the chamber's long axis when they're fired anyway.

 

[kelbro]

Using the bushing die, i tested sizing all most 100% of the neck, compared to about 50% . The ammo with the largest unsized neck area was the most accurate after the neck expanded to the rifles chamber, about 2 or 3 firings.

Could this also happen due to reduced neck tension? Less surface area 'gripping' the bullet?

So many variables in this game!

 

[hokeyplyr48]

Newbie question here but does FLRS or Neck sizing push the shoulder back? Or is there a specific die that does that?

 

[243winxb]

Could this also happen due to reduced neck tension? Less surface area 'gripping' the bullet?

I am almost sure centering the bullet in the chamber is more important than neck tension in a factory rifle. As long as the tension is equal. I use the largest bushing that will keep the bullet from moving. One thing you have to watch when only sizing 1/2 of the neck is, if the bullet is seated to deep, the bullet can fall into the case. The bearing surface on the bullet is very small.