224V Federal Brass too short?

[Subwrx300]

So have some interested data for the 224V. Data listed below but essentially, new brass seems to have very different shoulder angle/depth than fired brass. So either Federal is severely undersizing their new brass (bulk bags) OR my chamber is cut with reamer that is out of spec. Based on my measurements though, it seems more like Federal brass is slightly out of spec with SAAMI print. Note your measurements WILL be different as only applicable to my gauge, but the relative changes should be repeatable with others if there is an issue.

New Federal case (unfired) set calipers to .0000 against this value using a .330 shoulder gauge.
Fired Case (unsized) +.012 longer
Sized case (set for .0015-.002 bump) +.0105 (.0015 Shoulder bump back)

Pictures below but this *could* explain some of the odd accuracy issues people have been finding with the 224V when reloading. my groups with once-fired brass have been in the .3-.5 range with very little deviation during load dev. However, just shot a several groups with virgin brass and the pressures were higher (slightly more recoil and flatter primers) plus the accuracy was good but not great (.6-.9").

Check your new brass vs fired vs resized and see if yours is any different. looking forward to feedback as it makes me curious about others. Specifically, JP/Craddock barrels vs all the others; those two seem to be reporting good results from virtually all testers but curious about all that have a 224V. Thanks!

 

[Subwrx300]

To the top... Any one with virgin brass that can try this test? In my rifle, this causes groups to open up about .25-.5 mainly with flyers but also with SD/ES.

 

[Subwrx300]

So I did some math to compare SAAMI brass vs Federal brass vs my chamber (ie fired brass).

SAAMI shoulder midpoint to base =1.258 (min 1.251)
Federal new brass at .340dia shoulder = 1.247-1.248
Fired brass = 1.260-1.261

SAAMI CHAMBER spec is min 1.255 to max 1.265 which means mine should be around 1.262/3 or so accounting for brass shrinking.

So by my math, Federal is making their own brass for the their own cartridge too small! Not just on the short side of spec but past it by .005.

Can someone else versed in chamber vs brass spec check my math and tell me if this seems right/wrong? At the very least they cut the brass for the tightest/shortest chamber possible (which seems odd) and still .005 under that spec.

 

[Scotts556]

that's how brass comes. This stuff is made the same as ammo. It has to fit in ever chamber out there down to the smallest chamber that anyone could possibly cut and still be following the reamer print. This is why you "fire form" brass to a rifle.

Scott

 

[Subwrx300]

I have checked a few others in the past (factory Hornady 6.5cm, Starline, Lapua 308 and several 223) and none of them were more than .002 shorter than SAAMI cartridge spec. I definitely understand the need to fit all chambers and fireforming; didn't expect .012+ growth from new to fired.

Seems that they would put priority on tight tolerances since only one reamer print exists and they are in the driver seat on this one. Good way to make a bunch of people think the cartridge is less accurate than it actually is.

Thanks for the reply!