head space question and shoulder set back question

[biggdawg]

I am in the process of setting up my sizing die.

i am using my hornady head space gauge with the .375 bushing and measuring the shoulders of my fireform cases. I am getting quite a bit of variance on the shoulders of my once fired lapua brass. ranging from 1.1935-1.198. a new unfired case measures 1.185

then i have some hornady factory ammo i bought and fired it was 1.191 before firing and after they are very consistent at 1.197


i also have some 2 fire ppu wolf brass. don't have a before but fire form it goes from 1.1955-1.1965

my question is do i have a head space issue because of the variance in the lapua cases or is it because the shoulder started off so low?

my thoughts are to set back to 1.195-1.194

what are your thoughts? thanks

[stokesrj]

I think the issue is that the .375 bushing is to large, which moves you into the radius of the shoulder which results in inconsistent measurements the proper bushing is the .350 bushing which puts you in the middle of the shoulder.
Bob

[biggdawg]

thank you, i had the 350 and didn't know if it was right so i switch to the 375 i looked up on hornady and it said 375 for the 7.62x39 so that is what i used.

will recheck with the 350 and set back .002-.003 from there.

thanks again.

[Lead Chucker]

I use the 350, but I would bump the shoulder back .003-.005 for a auto depending on how tight your chamber is. .002-.003 is ok for a bolt gun. Just my .2 cents.

[biggdawg]

I use the 350, but I would bump the shoulder back .003-.005 for a auto depending on how tight your chamber is. .002-.003 is ok for a bolt gun. Just my .2 cents.

i set back .002-.003 for my other 2 ar's with out issue on is a 556 the other is a 7.62x40 so i will see. if i have problems i will bump them back more. I want to know why the new lapua brass is below minimum spec in length when new. my new cases measure 1.510-1.515 oal min is supposed to be 1.520

[Lead Chucker]

If .002-.003 is working ok for your gun and isn't having extracting issues then stick with it. I havn't even messured mine, but I would rather have them few thousandths short rather than long. They will grow as shot and sized.

[rg1]

I had the same confusion after buying Lapua new cases, Hornady 123 A-Max factory loads and sizing fired cases in my J&T upper. Here's a thread talking about headspace. My measurements using the .350 insert are at the bottom of the 1st page: (my 1st post, I didn't deduct the length of the case gauge--scroll to the bottom of the page for true dimensions)

http://www.65grendel.com/forum/showthread.php?633-Measurement-to-datum-line

[biggdawg]

i just remeasured some cases with the 350 insert and am getting similar results as everyone else.

new aa lapua cases 1.201-1.202 ave
new unfired hornady factory 123 amax ammo 1.207 average
i only had one case not sized after last night it is a wolf 1.2135
my sized cases are 1.209-1.21
i don't like to bump the shoulder anymore than i have to. it works in my 223 and 7.62 just fine.

will see what i get next trip, on a side note looks like 3 loadings is all i will get on the wolf. the primer pockets are getting pretty loose.

[bwaites]

i set back .002-.003 for my other 2 ar's with out issue on is a 556 the other is a 7.62x40 so i will see. if i have problems i will bump them back more. I want to know why the new lapua brass is below minimum spec in length when new. my new cases measure 1.510-1.515 oal min is supposed to be 1.520

There is a misprint on data, and everyone seems to have propagated that misprint. The actual minimum is 1.51, as I understand it. All new Lapua brass I have ever checked is on the small end of the spec, regardless of caliber. Hornady is closer to max spec.

[biggdawg]

There is a misprint on data. The actual minimum is 1.51. All new Lapua brass I have ever checked is on the small end of the spec, regardless of caliber. Hornady is closer to max spec.

thank you for that i was wondering why they were so short. so do you recommend trimming to 1.51?
max is still 1.526 right?

[bwaites]

I've never trimmed a piece of Grendel brass, period. I have 20+ firings on some Lapua brass and I've never trimmed.

IF I were a hypercompetitive shooter, I might consider it, but if it fits my chamber gauge after resizing, I load it and shoot! I've never had a piece grow out of the chamber gauge with any of the Grendels I've shot.

[bwaites]

There is a misprint on data, and everyone seems to have propagated that misprint. The actual minimum is 1.51, as I understand it. All new Lapua brass I have ever checked is on the small end of the spec, regardless of caliber. Hornady is closer to max spec.

I should clarify, as it wasn't really a misprint, so much as an understanding. The original data was set at 1.20-1.26. However, Lapua brass was considerably shorter than this, as noted. The 1.51 figure is consistent with NEW Lapua/AA brass, and AA has repeatedly said that new Lapua/AA brass does not need any prep before loading. That figure works under that understanding.