Issues bumping back the shoulder on brass

Very interesting. I'm going to follow this.

Was any annealing involved?

va_connoisseur said:

I ran into a strange situation today and wanted to get feedback from the horde on what could be causing the issue. Here's the situation. I am working on a load for my 6.5 Grendel. This is what happened.
I started with 50, four time fired Hornady cases. All the cases were fired from the same AR. Using the Hornady LNL progressive press, I de-capped the case. Then I bumped the shoulders back to my standard 1.208" measurement. And that's where things got interesting.

Of the 50 cases, 31 came out at 1.208 +/- 0.001". However, 19 of the cases had a headspace/shoulder measurement of 1.212 or greater, up to 1.214. And even when I ran them back through the Hornady sizing die, the shoulder measurement did not change. I took another few cases, from another group, fired from the same gun, not the original 50, and those five all bumped back to 1.208 with no issue.

I'm baffled. Any assistance or ideas would be helpful. Truth is, I can discard the cases and move on with the 31 I need for load development, however I am curious to what could be causing the issue with these cases.

TIA

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Do you anneal after every firing? Sounds like you've got some that have work hardened and resist keeping the bump (a lot of spring back).

What was the measurement before sizing?

How do you lube?

And you are certain the die didn't back out on the last few?

Is the brass from the same case lot?
Was it fired under the same conditions as the others: same load, same bullet, same general temps?

Campguy308 said:

And you are certain the die didn't back out on the last few?

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He addressed this by trying some other ones.

va_connoisseur said:

The measurement is typically 1.214-1.216 after firing

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Going from 1.214-1.216 to 1.208 is a LOT of bump and working the brass hard quickly, as evident this happening after 4 firings. Rather than bump .006" - .008", you might want to consider just going with .003 - .004" of bump . . . even less is better. Certainly, with that kind of bump your doing, annealing would help a lot.

Don's discard those cases you said you did as they can still work just fine . . . after being annealed and then sized again.

va_connoisseur said:

Thanks. I am going to start looking at the Annealez 3.0. Seems like one of the best budget annealers. Any other suggestions?

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I've been using one for about 5 years now and it's worked just fine for me.

Are the LNL bushings loosening up?

I ended up making shims out of soda can aluminum to keep/make my LNL bushings tight. There could be some slack there. Eventually I ditched the LNL setup. It wasn‘t as convenient useful as I thought when I started and the variability on the bushing fit bothered me.

A surprisingly small amount of difference in your case lube could account for some difference but it would likely be more random than this.

You are bumping your shoulders “a lot”. Although for a gas gun, I’d rather go big on the bump to avoid any feeding issues. My standard is .004” for bolt guns and all the way back to whatever factory specs for the case are for gas guns. Some guys swear by as little bump as allows the cartridge to chamber...they will swear that .002” is almost too much. I haven’t found it to matter at all for accuracy (SDs or on paper) and I anneal every time so it also doesn’t change my case life. For an AR platform, I’d keep doing like you are and accept that you won’t get the same case life that you might get from a delicate bolt gun. My only “large frame” AR “failures to feed” trace back to not sizing the cases enough.

It’s pretty likely that some of the cases are just work hardening from the sizing/firing cycle faster and are thus responding to the sizing differently. You could anneal, or sort out and discard anything that’s not sizing as it happens, or even toss the whole batch and start over. Kinda depends on your budget, tolerance for tedious busywork, availability/cost of brass, etc.

Personally, I’d discard the brass and start over with new before I got involved in gas flame annealling. For me, it’s AMP annealer or not at all. But I’m in the minority on that. Lots of guys love the anal-ease.

I crack myself up.

Good luck. Don’t blow your face off or burn down your house.

I was in a hurry and skipped annealing once. Had to give the sizing die an eighth or so of a turn to get it to bump the shoulder back far enough. The next 50 cases I annealed, then had to adjust the sizing die back out again. 6.5CM Prime which I think is Ruag (sp?) brass. Now I anneal after each firing.

va_connoisseur said:

Thanks. I am going to start looking at the Annealez 3.0. Seems like one of the best budget annealers. Any other suggestions?

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I have been using one for a couple years with great results.

ECK said:

I was in a hurry and skipped annealing once. Had to give the sizing die an eighth or so of a turn to get it to bump the shoulder back far enough. The next 50 cases I annealed, then had to adjust the sizing die back out again. 6.5CM Prime which I think is Ruag (sp?) brass. Now I anneal after each firing.

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This is exactly why I bought a set of the Redding Competition Shell Holders. I set my bump zero on the +.006 shell holder. That gives me .004" on either side to get more or less bump with just being able to switch a Shell Holder out. I use such of a variety of brass it gives me a lot of latitude. Works well for me since all of my 308 brass was free, once fired bolt gun brass.

My 308 die has enough slack in it to do that. Some dies may not.

If you're using a standard full length sizer with an expander ball, there could be enough friction pulling the case over the expander to stretch the neck/shoulder area.