Measuring shoulder setback findings

[Bartojc]

As I load for more and more different calibers and rifles I finally bought a set of the Hornady headspace comparators. I'd like to make sure dies are adjusted correctly and keep shoulder setback to a minimum when doing full length resize.

Been messing with 30-06 reduced recoil loads, and I've probably shot upwards of 50-60 rounds in my rifle. These were shot once in someone else's rifle, and then resized and loaded with a reduced charge and shot by me in my rifle.

I also have a hand full of factory brass shot once (Remington) in my rifle.

When checking the cartridge length to the shoulder I notice the reduced loads are a little shorter up to .004 ish than the full power factory loads. Is this because the reduced charge is really not stretching the brass the full length of the chamber ? Keep in mind the first time I resized I also did not set up and compare using a comparator.

Also when comparing fire formed brass what kind of variance do you see ? Is it normal for the different lengths to vary .001 +/- ?

I resized some fire formed brass and pushed the shoulder back ~.002 as measured. Not sure it'll help my groups at all, but at least it'll be a little easier on the brass.

-Jeff

 

[Walkalong]

When checking the cartridge length to the shoulder I notice the reduced loads are a little shorter up to .004 ish than the full power factory loads. Is this because the reduced charge is really not stretching the brass the full length of the chamber ?

also when comparing fire formed brass what kind of variance do you see ? Is it normal for the different lengths to vary .001 +/- ?

Yes, and yes.

 

[Bartojc]

Thanks Walkalong. Any issues I should watch for with reduced loads premature case failure ? I'm using 4895 at about 80-85 percent of max.

Thanks

Jeff


Sent from my iPad using Tapatalk

 

[Walkalong]

Not really anything different from normal loads, it just isn't as hard on brass.

Do realize it isn't filling the chamber on the first shot, so if you simply keep the shoulder there you will be OK.

If you want to get an idea where the shoulder is when the case is close to full chamber length, then hammer one case with three or four full power loads and measure shoulder position. That is where you want to be about .003 from.

 

[MtnCreek]

If you wanted to, you could increase cartridge headspace length with a full length sizing die set up to stay off the shoulder.

 

[Bartojc]

If you wanted to, you could increase cartridge headspace length with a full length sizing die set up to stay off the shoulder

I've set my resizing die to push back the shoulder of a case fired in my rifle ~.002. Measuring a good handful of cases fired with reduced loads I see that I will not touch many if any shoulders of those cases. So, you are saying they would like grow a little with the resize since I am off the shoulder slightly ?

Thanks for the info guys.

-Jeff

 

[MtnCreek]

They might. When the FL die squeezes the case body in to reduce it's dia, that moves the shoulder slightly forward.

 

[Bart B.]

Compare the case headspace on a new round before and after firing. They grow a little when fired.

Rimless bottleneck case loads reduced more than 10% from max typically end up with less case headspace after firing. The impact of the firing pin drives the case hard enough into the chamber shoulder to set the shoulder back a little. More than .005" has been observed with arsenal .30-06 cases.

If there's not enough pressure to expand the case so its back half stretches back against the bolt face, the primer will end up sticking out past the case head and case headspace will be less than it was before firing.

I've noticed this with 30-06 and 308 Win cases. So I don't think cases headspacing on their shoulders should be loaded more than about 10% less than maximum; no less than 45 grains of powder if 50 grains is listed as maximum.

 

[Walkalong]

When we were "fireforming" neck turned .220 Russian cases in 6 PPC rifles many folks said to use midrange loads. I always said to use full power loads to more fully form them. Most used midrange loads though.

 

[HankC]

When we were "fireforming" neck turned .220 Russian cases in 6 PPC rifles many folks said to use midrange loads. I always said to use full power loads to more fully form them. Most used midrange loads though.

If midrange load fire-forms, why 10% from max cannot stretch brass back to length and end up shorter?

 

[fguffey]

If midrange load fire-forms, why 10% from max cannot stretch brass back to length and end up shorter?

Shorter from the case head to the shoulder or shorter from the case head to the end of the neck?

F. Guffey

 

[fguffey]

If midrange load fire-forms, why 10% from max cannot stretch brass back to length and end up shorter?

Because there is a belief the case is not fully grown until it has been fired at least 4 times and by that time things have gotten complicated. By the time the case has been fired 4 times the case has work hardened and the ability of the case to resist sizing has increased. And then there is that old saying the reloader must start over by full length sizing.

The ability of the case to resist sizing and the ability of the press to overcome resistance to sizing become obvious when the shell holder no longer contacts the bottom of the die when full length sizing to minimum length.

So I ask when measuring the case are the measurements taken from the shoulder to the case head or from the case head to the mouth of the case?

F. Guffey

 

[HankC]

Because there is a belief the case is not fully grown until it has been fired at least 4 times and by that time things have gotten complicated. By the time the case has been fired 4 times the case has work hardened and the ability of the case to resist sizing has increased. And then there is that old saying the reloader must start over by full length sizing.

The ability of the case to resist sizing and the ability of the press to overcome resistance to sizing become obvious when the shell holder no longer contacts the bottom of the die when full length sizing to minimum length.

So I ask when measuring the case are the measurements taken from the shoulder to the case head or from the case head to the mouth of the case?

F. Guffey

Rimless bottleneck case loads reduced more than 10% from max typically end up with less case headspace after firing. The impact of the firing pin drives the case hard enough into the chamber shoulder to set the shoulder back a little. More than .005" has been observed with arsenal .30-06 cases.

I believe it refers to measure from the shoulder. I ask because I like to reload to reduced load and multiple times.

 

[Bartojc]

I believe it refers to measure from the shoulder. I ask because I like to reload to reduced load and multiple times.

In the original post, yes I was measuring from the shoulder. I assumed the replies were as such as well.

-Jeff

 

[fguffey]

Rimless bottleneck case loads reduced more than 10% from max typically end up with less case headspace after firing. The impact of the firing pin drives the case hard enough into the chamber shoulder to set the shoulder back a little. More than .005" has been observed with arsenal .30-06 cases.

I believe it refers to measure from the shoulder. I ask because I like to reload to reduced load and multiple times.

I would suggest you decide what is meant by a maximum load and a starting load. If the maximum is 50 grains 45 grains could be considered a starting load; I would not call the starting load a reduced load. The difference between 50 and 45 is 10%.

A shooter called me from a range; he wanted to know what is going wrong with R-P ammo, I suggested he call R-P. It was not long after that he shows up with 5 rounds that failed to fire with 15 cases that did fire. The 5 rounds that failed to fire were passed around to every shooter on the range that had a 30/06. The shooter made 3 attempts at firing the 5 cases and at least 3 attempts were made by 3 other rifles. Outside of the big dents in the primers the ammo looked good. I measured the failed to fire ammo in all of the usual ways, I compared the failed to fire rounds with the fired cases and was surprised the chamber in the new rifles kept the cases on the minimum length side. The fired cases would chamber in my chamber gages.

We pulled the failed to fire ammo down and checked the components; I was impressed with dimensions and weight. I removed the primers and then reinstalled them; after installing the primers I chambered the primed cases into one of my M1917 rifles with killer firing pins and busted the primers one by one. After busting the primers I measure the length of the cases from the shoulder to the case head again and my killer firing pins did not shorten the case from the shoulder to the case head.

Before that I chambered 8mm57 ammo in one of my 8mm06 chambers and then pulled the trigger. For the shoulder of the 8mm57 ammo to get to the shoulder of the 8mm06 chamber shoulder the cases would have to travel .127" forward. And after firing the shoulder and neck would still be there; that did not happen, I ejected the case after firing and found the case only had a hint of a neck and the case head never left the bolt face; meaning the shoulder on the 8mm57 round did not move.

Back to the failed to fire ammo; the failed to fire ammo was hit with firing pins at least 5 times each, after all that pounding the cases did not shorten between the shoulder and case head. The rifle was a new Ruger and the shooter was using new R-P ammo.

I would like to know if you are using starting loads or reduced loads, if you are using reduced loads as in "I like using reduced loads" I would like to know how much you are reducing them. I personally think reduced loads are cute; I have a narrow window when measuring powder, the narrow window is between starting and maximum.

And I would like to know what rifle, make and model you are shooting. A friend called and said he just experienced case head separation and I asked; because? He said he could not close the bolt on his reloads so he continued to shorten the case between the shoulder and case head until the bolt would close.

F. Guffey

 

[Bartojc]

In my case max for H4895 in my book ( not sure which one off hand) is 52.7 gr under a 125 grain bullet. 15% down is 44.8 grains. I'm loading at 43.5 gr to 45 grains. My best groups were at 45. No chrono so I'm not sure what velocity is but my POI is approximately the same as 150 grain Remington Core-Lokt factory loads @ 100 yards. Rifle is a Winchester Model 70 XTR Featherweight with 22" barrel. Kicks like a mule with factory loads. Not so bad with my loads. The whole idea was to be able to shoot it more often, and to be able to enjoy it. With load development I've been able to do that so the recoil must be less If I can get consistent groups at ~1" -1.5" @ 100 yards it'll be good enough for me for Deer hunting. I'm close

-Jeff

 

[fguffey]

The whole idea was to be able to shoot it more often, and to be able to enjoy it. With load development I've been able to do that so the recoil must be less If I can get consistent groups at ~1" -1.5" @ 100 yards it'll be good enough for me for Deer hunting. I'm close

As long as you understand the lighter bullet and reduced load can create problems with sealing the chamber. You claim the case is not forming to the chamber; that is indicative of low pressure and to finish the story you should have protruding primers. That is not to say the case shortened when fired; if you do not know the length of the chamber from the shoulder to the bolt face you do not know the difference in length between the case from the shoulder to the case head and chamber from the shoulder of the chamber to the bolt face.

I do not use reduce loads, when I want less recoil I choose 7.65mm53, 7mm57, 257 Roberts etc. I understand choosing a rifle based on recoil is not an option available to everyone.


F. Guffey

 

[ssyoumans]

In my case max for H4895 in my book ( not sure which one off hand) is 52.7 gr under a 125 grain bullet. 15% down is 44.8 grains. I'm loading at 43.5 gr to 45 grains. My best groups were at 45. No chrono so I'm not sure what velocity is but my POI is approximately the same as 150 grain Remington Core-Lokt factory loads @ 100 yards. Rifle is a Winchester Model 70 XTR Featherweight with 22" barrel. Kicks like a mule with factory loads. Not so bad with my loads. The whole idea was to be able to shoot it more often, and to be able to enjoy it. With load development I've been able to do that so the recoil must be less If I can get consistent groups at ~1" -1.5" @ 100 yards it'll be good enough for me for Deer hunting. I'm close



-Jeff

I worked up some reduced loads this weekend using my Winchester model 70 with 22" barrel.
125 gr Nosler Ballistic tip, 3.170", CCI LR primers and H4895 powder.
5 shot averages
42gr H4895 gave 2,327 FPS
43gr gave 2,499 FPS
44gr gave 2,486 FPS weird
45gr gave 2,583 FPS
46gr gave 2,647 FPS

With the 30-06 case and reduced loads you are very susceptible to powder forward, powder back velocity swings.

These were my results without any issues. Groups were under an inch at 50 yards.

Work up any loads carefully and verify any data before following it.

 

[Bartojc]

I worked up some reduced loads this weekend using my Winchester model 70 with 22" barrel.
125 gr Nosler Ballistic tip, 3.170", CCI LR primers and H4895 powder.
5 shot averages
42gr H4895 gave 2,327 FPS
43gr gave 2,499 FPS
44gr gave 2,486 FPS weird
45gr gave 2,583 FPS
46gr gave 2,647 FPS

With the 30-06 case and reduced loads you are very susceptible to powder forward, powder back velocity swings.

These were my results without any issues. Groups were under an inch at 50 yards.

Work up any loads carefully and verify any data before following it.

I know it's been a few weeks, but ssyoumans which load out of the above had the best groups, or were you not paying attention to that ? Right now all mine are close, but 45 seems to be most consistent. It's the highest I've gone, thinking of going 45.5 and 46, although I've already went ahead and loaded 20 rounds "in case" for hunting season

Can we ever be happy ? There is always another load to try isn't there ?

-Jeff

 

[ssyoumans]

I don't have the targets with me but they were all sub-1" at 50 yards I think the best in my rifle was at 45gr. I'll look this evening.

 

[Hummer70]

You might think about annealing the case necks as expanding/contracting is rough on the thin material which is likely about .014" thick.

I have a 30.06 case I loaded as you have and it had 157reloads on it when I stopped the test. It is still on my bench (somewhere) waiting for me to get back with it.

Also if you are lucky enough to have got a rifle chambered with a reamer at the end of its life you are lucky and the dimensions will be smaller thus less case stretch.

 

[Bart B.]

A friend and I both ran tests with a Federal .308 Win case shooting max loads in SAAMI spec chambers.

I got 47 reloads on mine; he got 57 on his. We stopped when our batches of IMR4895 powder ran out. Our load was 42 grains; under 168's for his, 165's for mine. No annealing whatsoever and we both used RCBS standard full length sizing dies I honed their necks out to about .335".

Our cases shortened about .002 inch after firing then grew that plus another .001" after full length sizing setting shoulders back about .002". We trimmed 'em back to 2.000" after they grew to 2.010" long.

Some people have got over 80 reloads on WCC58 .308 match brass that weighed about 150 grains; thinnest walled cases for .308's I know of.

 

[Walkalong]

If you don't work the brass much it will last a long time. If you work it a lot, it won't. Annealing can help in those instances.