neck sizing vs. full length sizing - bolt guns

[Bart B.]

Poper asks about my lapped-out full length sizing dies:

Interesting. Does this mean you outside neck turn or inside neck ream all of your brass to get uniform neck wall thickness and thus uniform tension on the bullet? If so, what is the min/max neck wall thickness you find acceptable?

The case used in this test wasn't neck thickness uniformed; neither outside turned nor inside reamed. Its wall thickness from the factory was about .013- to about .014-inch. I don't outside turn case necks that are within a thousandth inch in thickness spread. Used to, but there's other things more critical to 1/2 MOA accuracy at 600 yards than perfectly uniform case necks.

There's six regular RCBS full length sizing dies at my bench with necks incrementing from .332- to .337-inch. I just use the one that works best for the batch of cases I'm sizing.

Something vague comments:

Who says that a Ruger M77 can't shoot?

The 1992 US Palma Team says so. At least for the 20 M77 single shot versions in .308 Win. Ruger built for them as a gift. Their barrels were made by Green Mountain; a New England barrel maker catering to black powder folks. Ruger didn't know back then what a top quality match barrel needed nor did they show any knowledge of custom barrel makers who were that might offer some advice. Ten were 4 groove and ten had 6; the 6-groove ones were the worst for accuracy. 19 of them had "improved cylinder bore" accuracy as coined by one team member disgusted with the horrible accuracy his produced and the name stuck.

Poor stock design, triggers and bedding along with poor barrel quality of these 19 is why all but one team member chose to use his own rifle. They only one used was so-so at best but the team member who used it had his own rifle break and that was the only one he had available at the time.

 

[something vague]

I believe Ruger has tackled the out of house barrel manufacturing. It is too bad that the reputation has stuck with them to this day. But then again, i'm not trying to shoot 1/4MOA at 600yrds either. I am by no means trying to make comparisons of my accuracy, of what is really no more than a hunting rifle, to Palma class rifle competition.

 

[jon_in_wv]

Is it ok to have cases that are longer than the 2.015 spec? My lee cutter will trim them down to 2.005. I know that headspace in .308 is important, if the neck is too long, it'll pinch the neck in the chamber upon firing, pressure skyrockets, which equals a bad day

You answered your own question friend. Max lengths are there for a reason. Play it safe.

 

[Redneck with a 40]

Yeah, I'm keeping my cases well below the 2.015 spec, no point in messing around with that, as it could destroy my very nice rifle.

 

[flashhole]

I think Bart B's assertions of FL sizing holds truer for guns with tight or match chambers than is does for generous chambers. I see no difference FL or neck sizing with my 221 Firball or 223, both with very tight chambers. Not the same for my 25-06. That chamber is overly generous (it happens to be a Ruger 1V). It benefits greatly from neck sizing only. It also benefits from re-formed brass 30-06 to 25-06 because the neck thickness increases and reduces blow back. The re-formed, fire-formed brass made a significant improvement in accuracy in my gun. My neck sizing die is the Lee Collet Neck die. It works great.

 

[Bart B.]

flashhole comments:

I think Bart B's assertions of FL sizing holds truer for guns with tight or match chambers than is does for generous chambers.

My assertions hold true for any chamber size; generous, SAAMI spec and tight.

Tight (match) or generous (military and often factory) chambers don't hold a loaded rimless bottleneck round any better than a standard SAAMI one. They all have the loaded round's back end pressed off center in the chamber by the extractor and center the case shoulder in the chamber shoulder (and therefore the case neck in the chamber neck, too) when the firing pin strikes the primer and fires the round. A couple thousandths inch up or sideways difference in the round's position at its back end for each chamber type is insignificant.

 

[MCMXI]

Bart. B, I've read your comments here and on an older post where you state that full-length sized cases give better accuracy than neck-sized only cases.

http://www.thehighroad.org/showthread.php?t=441672

I just read your previous thread again and have taken the liberty to cut and paste the relevant sections and use bold type to highlight the pertinent sentences.


"Firing pin force sets the case shoulder back a few thousandths of an inch as it dimples the primer cup crushing the priming compound detonating it like a hammer on a match head. And the neck gets a tiny bit longer, too. Now the case head is further away from the bolt face by the same amount the shoulder was set back. This is the only time the loaded round is in the most critical position for firing. Any variable in how the bullet’s positioned at this time effects accuracy.

Both neck-only and full-length sized cases will be, for all practical purposes, fit the chamber the same way. The exception is full-length sized ones will have their back end a tiny bit further off center and the neck-only sized ones may not have their case necks holding the bullet as perfectly aligned with the chamber. If bullets are seated out enough to set back a few thousandths when pushed into the lands when chambered, this will help a tiny bit with their alignment to bore center providing the case necks are well aligned and centered with the shoulder.

From these situations, it should be easy to see than the only significant physical difference between neck-only and full-length sized cases when they’re fired is back at their pressure ring. Neck-only sized cases will have a body diameter a couple thousandths of an inch larger than a full-length sized one. Either one has their case shoulders’ centered just at the chamber shoulder when fired. Their back ends will be pushed off center by the extractor about half their difference in diameters at the pressure ring. Full-length sized case with its smaller diameter will be off center by only a thousandth of an inch; maybe two at the most. At the bullet’s tip, it’ll be tilted off center by about one-third that amount at the most; not enough to make a difference which doesn’t matter much any because whatever angle it is at will typically repeated for each shot.

I’ve noticed one interesting difference between neck-only and full-length sized cases in one very important area. Remember how the case shoulder centers the front of the round in the chamber, especially the neck holding the bullet? Measuring sized cases for neck runout showed me that full-length sized cases can have straighter necks than neck-only sized ones. Which makes sense to me as neck-only sizes the neck on a case whose body is not supported by anything to keep it in alignment with the neck during the sizing operation.

Setting the fired case shoulder back only a couple thousandths with the case body held tight in alignment with its neck tends to keep the neck straighter and better oriented with the shoulder. I’m convinced that when the full-length sized round fires with its shoulder hard and perfectly seated against the chamber shoulder, its straighter neck lets the bullet enter the rifling with less distortion therefore shooting more accurate. I’m also convinced this is why fired cases properly full-length sized in dies with lapped out necks typically shoot more accurate than neck-only or partial-neck sized fired cases.


In summation, you contend that full-length sized cases produce better results in terms of accuracy because a full-length die (with a lapped out neck) does a better job of maintaining concentricity between the neck and the body of the case as well as producing a straighter neck. Your whole argument is based on the single assertion that neck-sizing dies don't adequately support the body of the case during the sizing process. Would this be a fair synopsis?

OK, now I've made sense of your posts, I will respectfully disagree with your argument that ALL neck-sizing dies don't support the case sufficiently based on empirical evidence. I use Redding neck-sizing dies and the runout of my .300 Win Mag cases (W-W Super) fired three times and neck-sized only after each firing is +/- 0.0005". Now if that's not sufficient concentricity then I don't know what is. Personally, I've always found that neck-sizing only produces better results than full-length sizing for all of my bolt action rifles without exception. Then again, I do use what I consider to be top quality dies.

This is a very interesting discussion and I will add that IF the majority of the long-range benchrest world records are set by shooters that full-length size their cases rather than neck-size only, then I will certainly consider packing my neck-sizing dies away. However, many of the shooters don't specify what they do so it's hard to know what's going on. I know that Ken Brucklacher used brand new, unsized Norma brass when he set his 100-8X heavy gun world record!!

 

[fguffey]

45Badger, I use one die to size cases for perfect chambers (go-gage size), I use the same die to size cases for a field-gage length chamber, the difference, my dies have threads, I do not have to decide either/or (neck size/full length size), I have 9 choices between go-gage and field-gage length chambers. Again, I use a feeler gage to adjust (or limit) the amount of sizing, I can not control ram travel but I can adjust the gap between the die and shell holder by adjusting the die.

The best of all worlds when sizing is neck sizing with case body support and limited shoulder set back, if the chamber is perfect and the gap between the shell holder and bottom of the die is .004, the shoulder set back is .001. Again, I have an Eddystone M1917 that has .016 head space, when sizing fired cases from that rifle the gap is at least .014.

Neck sizing only with a full length sizer has an advantage, the portion of the neck that is not sized AIDS in centering the case in the chamber.

Neck sizing with partial body sizing and limited shoulder set back cuts down on case travel (stretch between the web and body of the case).

Bad habit: Guesstimates, guessing the gap in fractions of a turn, purchase a machinist feeler gage, most start out at .001, other start at .0015. the gage allows for repeatable adjustments, this helps when head space is known (to the thousands) instead of go, no and beyond, with a feeler gage I have 9 options, with short chambers I have 17 options.

F. Guffey

 

[Bart B.]

1858 remarks:

This is a very interesting discussion and I will add that IF the majority of the long-range benchrest world records are set by shooters that full-length size their cases rather than neck-size only, then I will certainly consider packing my neck-sizing dies away.

I'm basing my assertions on what top high power match rifle shooters have done properly testing their rifles and ammo for accuracy. 98% of their 15+ shot test groups with proper full length sizing are smaller than 98% of any benchrest discipline records for groups of 10 shots or more using any neck sizing technique.

I don't consider 5-shot groups statistically significant for comparisons as they are more luck than typical. These and the single 10-shot ones are rarely, if ever, repeated by the same rifle/ammo combinations. If a batch of ammo shoots ten 5 shot groups, the smallest one represents what the ammo does only 10% of the time. A single group with 20 or more shots is a much better measurement and is much closer to reality and what one can count on all the time. The best of these from high power match rifles using full length sized cases are smaller than the aggregate of several 5- or 10-shot benchrest ones.

But high power competitors don't shoot tiny groups stoolshooters make all the time. Few people realize how accurate their rifles and ammo have to be to do as well as they do. In their steadiest postion (prone) the best ones are holding a 3/4ths MOA area on target trying to break their shots inside a 1/2 MOA area watching their aiming point bounce around from their heart's pulse beat while doing their best with a 1 to 3.5 pound trigger. And making wind corrections based on heat waves wrinkling across their spotting scope's field of view just before each shot. And they're trying to shoulder the rifle at the exact same position with the pressure and tension between body and rifle the same for each shot. At the longer ranges where wind, muzzle velocity and ballistic coefficient spread open up groups, they throw parties if they keep all their 20 record shots inside a 1.5 MOA area. A benchrester shooting his rifle virtually untouched in free recoil with a 2-ounce trigger would hide his head in shame if that was the best he could do.

 

[something vague]

Wouldn't a 20 shot or more group be less of an accurate measurement of the rifle's and ammo's accuracy capabilities? Aren't we testing what our ammo could potentially produce with as little outside influence as possible? In my experience, which is limited btw as I am still new, I have found myself to grow tired at about the 15th round and beyond. My eyes don't focus as well and my steadiness begins to be comprimised. It may be very little but is noticeable. Not only do I become the issue but my rifle does as well. Fouling begins to increase and barrel temp begins to rise, even with long breaks between shots. My goal for testing my loads is to try and evaluate what it is capabale of with all things as perfect as possible. My procedure then becomes shooting 5 shot groups, with plenty of rest in between. I will also clean the bore every other group to keep conditions fairly constant. Once I find what I believe to be the best, then I will start shooting groups without worrying so much about the other influences that could comprimise accuracy. I try to run my testing as if it were a scientific experiment. Like I said though, I am still new to this aspect of shooting. This may not be the correct way to go about testing but has worked for me. BTW, sorry as I may have gone slightly off topic.

 

[MCMXI]

Bart, your last post was all very interesting, but can you answer my question at the end of my "summation" as to why you believe full-sizing results in better accuracy.

"In summation, you contend that full-length sized cases produce better results in terms of accuracy because a full-length die (with a lapped out neck) does a better job of maintaining concentricity between the neck and the body of the case as well as producing a straighter neck. Your whole argument is based on the single assertion that neck-sizing dies don't adequately support the body of the case during the sizing process. Would this be a fair synopsis?"

In other words, if a neck-sizing die could support the case body properly during sizing, wouldn't a neck-sized case produce equal or even superior accuracy compared to a full-length sized case?

 

[Walkalong]

Interesting stuff...............I don't know much about High Power or F Class etc, but I do know a thing or two about 100/200 yard Benchrest. It is in a category all by its self IMHO. The big dogs routinely shoot aggs under .2500 (1/4") range in any but the worst conditions. If you agg in the two's, it better be tough conditions that day, or you won't be top dog, usually. (Oh, and I'm just a little dog, although I shot like a big dog some days)

 

[Bart B.]

1858, a fired case solidly held by its body when neck sized may work well. One would need a floating die tapered exactly like the fired case body to do it.

The issue, to me, seems to be the way the case fits the chamber when it's fired as that's the only place where things differ. I'm aware of some of the differences but probably not all of them. I'm not sure anyone knows all the reasons why their full length sized reloads shoot more accurate than any neck only sizing process.

First learned about this from National champions and record setters in the high power rifle game as well as Sierra Bullet's ballistic technician who reloaded their test cases to shoot their bullets for accuracy tests. Testing was done with rail guns in Sierra's test range or shooter's complete rifles clamped at fore end and butt stock in machine rests; both methods eliminate all human influences.

My own tests with Neil Jones' neck sizing dies and RCBS and Bonanza standard and neck-lapped full length sizing dies making reloads then tested shooting prone with the stock's fore end and toe on sand bags shooting 20 to 30 shot test groups were almost as accurate as those from mechanical devides.

Regarding bullet runout, depending on how one mounts the case against the dial indicator, different amounts and directions of runout will be seen.

The way one tests their shootin' stuff makes a big difference in results they get. Few people shoot heavy recoiling rifles with 1 or more pound triggers accurately when the rifle's held atop rests of any kind on a bench. I don't and know the sights zero at different places between bench shooting and standing. Even the benchresters know that and their rifles are shot in free recoil; untouched by humans except for light finger pressure on their few-ounce triggers.

 

[MCMXI]

Bart, some excellent points and much to think about ... thanks.

 

[Bart B.]

1858, there's another thing that's at issue: How one measures accuracy.

I couldn't care less about what size the smallest group of several is. The reason is every other group is bigger. How much bigger is the only thing to me that counts. I ain't impressed by those lucky, tiny 5-shot groups benchresters drool over. Tiny 10-shot ones interest me. And tiny 20-shot ones get my attention. 30- to 40-shot tiny ones impress me.

My accuracy standard is what the largest group for a given load is. I know all the rest are smaller. The largest one is what I can expect or count on all the time. Anything smaller is fortunate; the smallest one is 99% pure luck.

 

[Walkalong]

I wouldn't go as far as 99%.

 

[Bart B.]

Walkalong's comment on my percentages:

I wouldn't go as far as 99%.

Well, how often does one best his smallest of the last 100 groups he's shot in a benchrest match?

 

[MCMXI]

Bart, I'm not obsessed with group size but it's important to me during load development. My main interest is the ability (rifle, load and shooter) to put a hole in a 1 MOA target on the first attempt, under all conditions, anywhere from 0 to 1000 yards.

But you make more excellent points. How do we measure accuracy? Most of us don't mount our rifles in a rigid rest during load development so there's probably a lot of human error in the data. I know my load development suffers from human error but I can see trends from week to week and I use the same technique for load development that I use when shooting matches.

 

[Walkalong]

how often does one best his smallest of the last 100 groups he's shot in a benchrest match?

That is picking nits. How often can one shoot a little bug hole? Much more often than you can best your best ever obviously. You can't just throw out the little ones any more than you can ignore the big ones.

That is why we shoot aggregates, and not just one group. Same as the High Power guys don't shoot one target and call it good. A combination of groups or targets will bring the best shooters to the forefront. That is why some names are always in the running at the end of a weekend, or week.

 

[Bart B.]

Walkalong, I may be picking nits but it's the nits that luckily set all those benchrest records. But after all the reloading's done, one will stand a better chance of shooting tiny groups when his biggest one is as small as possible.

 

[Walkalong]

one will stand a better chance of shooting tiny groups when his biggest one is as small as possible.

Can't argue with that part. We all want a rifle/load that gives us a chance to shoot great every time. If we don't shoot well we want it to be us, not the rifle. The more variables we can eliminate, besides the nut behind the trigger, the better. (Oh, and some shots do blow "into" the group accidentally, same as they "blow out" of the group due to error.)

I still disagree that it is entirely luck when one shoots a tee tiny bug hole, which I agree is almost impossible to replicate at will, and very hard to do at all, but it keeps getting done. I mainly discount it being all luck because it's always the best shooters that do it regularly. I have a couple of screamer patches, but I know folks with buckets full of them. It's probably 30% luck, 40% determination, and 30% skill for me. Give or take some percentage points.

Are all your great scores luck, I doubt it.

 

[Horsemany]

Bart B. wrote

I couldn't care less about what size the smallest group of several is. The reason is every other group is bigger. How much bigger is the only thing to me that counts. I ain't impressed by those lucky, tiny 5-shot groups benchresters drool over.

I can't believe you are discrediting benchrest accuracy in a discussion about precision reloading. I believe the discipline of benchrest is a far better indicator of accurate loading techniques compared to highpower. Benchrest eliminates more of the human element IMO.

For years the benchrest technique was neck sizing with Wilson bushing hand dies. Now about half I talk to full length size after every firing instead.

There is no greater indicator of precision reloading technique than that of top benchrest shooters. Highpower isn't even close.

 

[Bart B.]

Horsemany, high power match rifles tested for accuracy with full length sized cases at 300, 600 and 1000 yards shoot groups equal to or smaller than any bench rest rifle. Compare these to what match winning benchrest rifles do.

For example, one test had several 10-shot groups at 600 yards ranging from 1.5 down to 0.7 inches. One of the smaller ones was published in the American Rifleman for a bullet ad.

Another had 30 consecutive shots inside 7 inches at 1000 yards, half with new cases and half with full length sized ones.

40 consecutive shots with full length sized cases went into 1.92 inches.....at 600 yards.

20 shots with new Winchester cases, metered charges with a 3/10ths grain spread and bullets with up to 3/1000ths runout loaded on two Dillon 1050 progressive reloaders.......2.7 inches at 600 yards. Handloader magazine had an article with a picture of this group.

The above were done with Win. 70 actions.

7.62 NATO M1 and M14NM semiautos built by military armorers have shot 8 to 10 shots under an inch at 300 yards and with good ammo typically stay under 4 inches at 600 yards.

Here's one of mine from a Palma rifle with full length sized WCC60 cases:



Then if, by now, you're not a believer, call David Tubb, Mid Tompkins and all the other National Champions and tell them the sub 3-inch 600-yard groups they get testing their rifles and ammo with full length sized case are not very good.

In spite of good high power match and service rifles having these accuracy levels, the best groups they typically shoot winning matches are 1 to 3 MOA (or more) on bull's eye targets. Not what benchresters do, but usually the comparison made. With the physical environment high power rifles are shot in, that's all one can expect. If you don't already know what these physical issues are, then I'll be glad to explain them. But a good shot already knows what they are.

 

[Horsemany]

high power match rifles tested for accuracy with full length sized cases at 300, 600 and 1000 yards shoot groups equal to or smaller than any bench rest rifle. Compare these to what match winning benchrest rifles do.

B.S.

I've shot both and been to matches for each. A custom benchrest gun will put a highpower gun to shame all things being equal. Sorry but an iron sighted gun fired freehand will not compete with the level of precision a full blown bench gun can produce.

My Stolle Panda 6ppc with Krieger barrel will shoot 5 shot groups that look like 30 caliber holes. THis is not uncommon for benchrest guns. I've never seen a highpower rifle that can do that. No offense to highpower guns or competitors. It's just a different game. No shooting discipline puts more precision into the loading of ammunition than benchrest. By the time I expand necks, turn necks, ream primer pockets, and fireform I'll put easily 10 hours into 100 cases. And that's just case prep. Sorry Bart, it is what it is. That's not an opinion but fact.

Think about it Bart. Do you see anyone using highpower guns at benchrest matches? You know, the matches where groups are measured in thousandths of an inch?

 

[MCMXI]

I have to agree with Horsemany on this one until I see the current world records for non-benchrest high power rifles at 1000 yards. Here are the two latest world records for 1000 yard heavy gun benchrest ... both 10-shot groups and close to 3" at 1000 yards!!

April 18th, Joel Pendergraft of Durham, NC put 10 shots into 3.048″ to set a new IBS 1000-yard Heavy Gun World record.

Ken Brucklacher, current President of the Original Pensylvania 1000-yard Benchrest Club (Williamsport), joined the immortals this Sunday, May 3rd. Shooting a .300 Weatherby Mag with 240gr Sierra MatchKings, Ken set a new 10-shot Heavy Gun World Record score of 100-8X. The group size was pretty amazing too. A measured 3.137″