Different brass mfr. Different dimensions?

[Sgtsideways]

May be a a stupid question, but here goes. I was measuring the shoulders on 2-3x fired brass from Peterson, BHA, and Lapua. No resizing and the measurements were taken on fired 338LM using Redding dial comparator.
Correct me if I'm wrong here in what I'm doing. I separate the brass by mfr. and take the measurements with all rounds having had the same charge of powder. Peterson brass measured shoulders +- 0.003". BHA/Lupua measured +- 0.001" for the fired shoulders. What really struck me was how different the fired shoulders were from the 3 mfr's. with regard to measuring the headspace. There was a spread of 0.008" difference on headspace between the 3 sets of brass. I known the 3 are all different in how they are made and brass thickness'.
My confusion is how do you which headspace is the one to go with for setting the shoulders back 0.020" or more? I guess I was expecting the fired brass to expand the shoulder to match the chamber +-0.001" no matter what manufacturer the brass came from. BHA brass had the longest head space, Peterson the shortest of the 3 brasses.
Appreciate any help.

 

[918v]

Did BHA/Lapua have the longest shoulder measurement?

 

[SonoranPrecision]

All my brass ends up the same dimension after being fired (or extremely close). Did you deprime all the brass before measuring? If so, what method did you use?

 

[Sgtsideways]

Did BHA/Lapua have the longest shoulder measurement?

Lapua=2.270", BHA=2.273".

 

[Sgtsideways]

All my brass ends up the same dimension after being fired (or extremely close). Did you deprime all the brass before measuring? If so, what method did you use?

All deprimed. Measurements with dial comparator and Hornady comparator to double check.

 

[918v]

I’m guessing it’s due to different shoulder thickness/hardness between brands.

 

[jakelly]

Same loads in all brass?

 

[supercorndogs]

You are trying to set the shoulders back .001-.004, not .02. The ones you use to set the die, are going to be the longest ones. Test them to make sure they chamber with some resistance, or wont chamber, and you will be sure you have the ones you want to set up your die with. Move your die down slowly until you have achieved the desired bump, then make sure the case chambers freely.

 

[flyright]

All brass has different metallurgy. I have one die set up for Hornady brass and another set up for Lapua that happens to also work with Peterson. If I run the Lapua or Peterson through the die that's set for my
Hornady brass, it will not set back at all. If I run the H brass through the die set up for L&P it sets back .004 or more. This has made me settle on one or two brass types going forward.

 

[Graye2]

With some brass it may take several firings to get to “chamber length”. As said above size from the longest and process them the same for bump. After 2-3 firings they should all be the same and you’ll start to bump shorter ones as well.

However neck wall thickness may also (likely) be different. Are you using a full length sizing die, bushing, collet, etc? I would be more concerned around neck tension across different brass than shoulders as they will grow.

 

[Sgtsideways]

Same loads in all brass?

Yes. All at 83g IMR 4350

 

[Sgtsideways]

You are trying to set the shoulders back .001-.004, not .02. The ones you use to set the die, are going to be the longest ones. Test them to make sure they chamber with some resistance, or wont chamber, and you will be sure you have the ones you want to set up your die with. Move your die down slowly until you have achieved the desired bump, then make sure the case chambers freely.

Another senior moment....................DAAH! Yes, you are absolutely correct. I meant to say .002".

All brass has different metallurgy. I have one die set up for Hornady brass and another set up for Lapua that happens to also work with Peterson. If I run the Lapua or Peterson through the die that's set for my
Hornady brass, it will not set back at all. If I run the H brass through the die set up for L&P it sets back .004 or more. This has made me settle on one or two brass types going forward.

I starting to learn this the hard way. Thanks and yes I am rather new to reloading.

With some brass it may take several firings to get to “chamber length”. As said above size from the longest and process them the same for bump. After 2-3 firings they should all be the same and you’ll start to bump shorter ones as well.

However neck wall thickness may also (likely) be different. Are you using a full length sizing die, bushing, collet, etc? I would be more concerned around neck tension across different brass than shoulders as they will grow.

Thanks for that 1st paragraph, because that was going to be my next question. I do full length resize with Redding S type dies. Then use an expander mandrel for the necks. I shoot for 0.002" neck tension for the bolt action that I am using.
Since the BHA ammo shows the longest shoulders, I will set my die for that dimension and let the other brass "grow" to chamber length. I guess my only concern will be that the "short shoulder " brass will neck tension properly.

 

[Graye2]

The S die will be fine...they don’t size down all the way anyway. I have the competition set with the micrometer and I only size the top half or so of my necks as it allows the shoulder junction to align in the chamber. Just measure your wall thickness and use an appropriate bushing to accommodate and then run your mandrel through. In order to ensure you have expansion you will need to use the tightest bushing (for thinnest walls) or change bushings for each manufacturer if walls differ.

FYI - I also use SAC’s 6 Dasher die and his is set the same way (static)...only sizes the top half of the neck. I’m waiting on his new expander mandrel option to replace the decapper and if I like it I’m selling my Redding dies to accomplish everything in 1 step. (No .338 option though)

 

[Sgtsideways]

Great Graye2. I'll look them up.

 

[SonoranPrecision]

Wait. You are shooting 338 lapua with only 42 grains of Winchester 760? That sounds like an extremely light load. Is it possible that the load is too light to expand the brass fully?

 

[Sgtsideways]

Wait. You are shooting 338 lapua with only 42 grains of Winchester 760? That sounds like an extremely light load. Is it possible that the load is too light to expand the brass fully?

Yeah, I've been working on the 6.5 Creedmore loads and I had that on the brain. Thanks for catching that. That would be an interesting round.....Just call me squibby. Corrected to 83g IMR 4350 above. I'm wondering if I need to up the charge to 84g to fireform the shorter shoulder brass?

 

[SonoranPrecision]

Yeah, I've been working on the 6.5 Creedmore loads and I had that on the brain. Thanks for catching that. That would be an interesting round.....Just call me squibby. Corrected to 83g IMR 4350 above. I'm wondering if I need to up the charge to 84g to fireform the shorter shoulder brass?

That would completely depend on what weight bullet you’re shooting