Can brass shrink after firing, depriming, and resizing??

[Jamie]

As per the heading folks. I'm after some constructive advice concerning reloading my .223 Rem, with Remington brass for a 1 in 8 Tikka T3.

Either I'm going mad or some of my brass is shrinking!??

Is it possible for brass to shrink rather than stretch after firing, resizing and measuring again? I'm using a "Clarke" vernier, (which is accurate and consistent) with a Hornady comparator, which is accurate and consistent most of the time, if left as originally mounted for that batch of reloads. Although I appreciate their not as good as could be, but I do make sure they are flat on the vernier fingers.
Firstly, after de-priming and where possible just neck sizing, I always TRY and trim my brass back to 1.747".

However, before and after prepping, the brass always seems to vary from 1.750" down to 1.744".

Now if I just reloaded as is, with varying length brass from 1.750" to 1.744" surely this would affect pressures and distance from or to the lands???

Also would this make much of a difference in a consistent and accurate P.O.I from 100 yards, out to 250 yards?
I appreciate consistency is one of the keys to accuracy. And I've read a few posts stating that I should cut all my brass to the shortest length. But should I really be cutting them right down to 1.744"!!? Would this be a problem? Just to add that this wouldn't be a problem with powder compression, and the powder loads are the same, 25.1 grains.

As a side note, I do have around 200 pieces of once fired PPU brass, would I be better with that, as apposed to the Rem brass??)

Jamie

[Jagged 77]

When you fired the case it expands outwards to fit your chamber. The fired case could end up (by a few thou) slightly shorter then you originally trimmed it. By neck sizing only at this point you are leaving the body alone so therefore length will not change much. If you body or full length size you will see the cases lengthen.

 

I'd say don't get hung up about trimming at the ranges you are shooting at, just don't get them too long. A slight variation isnt really going to hurt much.

[Brummy Mark]

My 223 lap brass has shrunk too, dont worry about it, just keep an eye it.

Im on my 5th loading of cases now, i have 20 out of 100 that measured between 1.755 and 1.760 and they will need a full length/bump-back after this next firing, the other 70 odd cases are at 1.748 to 1.751 and will probably be good for just a neck size again.

I have only neck sized with lee collet die.

[Jamie]

Cheers folks,

So I presume you wouldn't recommend trimming all of them to the shortest then?

Cheers

Jamie

[gunner]

Hi jamie RE cutting to 1744 will be fine - i trimmed all my 223Ai brass 3 days ago to 1741 , the longest was 1755 i think . Iv had factory ammo that was only 1735 seriously ( back in my STD 223rem days ) dont worry ! besides if your after the best accuracy - then you allready know about uniformity

[Jamie]

Hi jamie RE cutting to 1744 will be fine - i trimmed all my 223Ai brass 3 days ago to 1741 , the longest was 1755 i think . Iv had factory ammo that was only 1735 seriously ( back in my STD 223rem days ) dont worry ! besides if your after the best accuracy - then you allready know about uniformity

Cheers Gunner!