Too much brass stretching?

[Viperdoc]

OK, so maybe it's not such a great idea to work up loads in winter, there's always trap shooting. Anyway, my fired 223 AR cases measure 0,253, unfired but loaded are 0.249 with a minimal neck turn to 0.0125 walls, and my necks are run through a 0.0246 type s die, which ends up being a hair less than 0.0247, yielding a neck tension a little less than 0.003.

So, the brass is going from 0.0246 to 0.253 every firing- is this so much to be too much? The reamer was a SAAMI min.

 

[RonAKA]

I suspect you can't go as tight in an AR as in a bolt gun. Also you need neck tension to keep the bullets from moving in the magazine. Probably what you have is very good, and better than most factory bolt guns. If you anneal every 4-5 loads or so, the neck should not split. I stretch my .264 WM necks close to double that, and they still last about 20 firings without annealing.

 

[fdshuster]

viperdoc: I spec'd my Pacific 223 Rem. reamer with a .253" chamber neck, just a few thousandths smaller than a standard 22 centerfire ( 222 Rem, 223, 22-250, etc), that I find to be in the .256"/ .257" diameter range. If your fired cases are measuring .253" I would think your chamber is .254", allowing for the .001" of springback, so they are really moving from your sized diameter of .246" to fired at .254". Still better than going from as sized (before using the neck expander) using a conventional one piece FL sizer of approx. .244" to the fired .256"/.257", a difference of .013". My Lapua 223 brass has a loaded neck dia. of .250", and I use a .248" bushing. I can say with confidence that I do get .001" case neck springback after firing because with all my chambering reamers, that's the measurement of the fired case necks: .272" 6BR reamer: fired brass is .271". .251" 22BR reamer: fired brass is .250". .262" 6ppc reamer: fired brass is .261", etc. Using Lake City brass in the AR's with factory chambers and a non bushing FL sizer, I get 13 to 14 loadings before the small neck splits begin. The Lapua in the tighter necks, with a bushing die have yet to show any splits and some of them are up to 16 and 17 loadings. I do not anneal.

 

[Viperdoc]

Thanks for the great response.I have been turning my 223 Lapua brass to 0.0125, although the last digit is sketchy of course. I have been running the brass over an expander mandrel first to fix the neck dings, turning (if not done already), then resizing with a 246 bushing.

Going from the 246 bushing to a 254 fired case seems like working the brass a lot each firing, but it sounds like the Lapua brass can take it, which is really encouraging.

 

[fdshuster]

viperdoc: You could use your Lapua as they come out of the box, without any outside neck turning, and like mine, the loaded neck diameter would be .250", size with a .248" bushing, and you would be saving a couple of thousandths. I really don't think there is any accuracy advantage in trying for a closer/tighter fit when using the ammo in an AR. As accurate as they can be they still have their limitations based on stock design, (the round handguard), the drop angle on the underside of the buttstock, etc. I save my tight fitted neck chamberings for the dedicated benchrest bolt-actions. Actually, I've compared carefully prepared 223 Lapua brass vs. the same carefully prepped Lake City in my Krieger barrelled uppers and have yet to see any advantage in using the $$$$ Lapua, so the AR's get a steady diet of LC and any quality Winchester I can find.