Thread: Sizing Question
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Old November 9, 2011, 02:50 PM   #10
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Join Date: May 27, 2007
Posts: 5,101
I typically size all my cases for hunting rifles full length, and, using an RCBS Precision Mic, take the cases (size) down -.003 less than what a fired case measures.

I've told a friend I will load him some .270 ammo for use in his Rem 7400 auto. His fired cases measure +.008 on avg. (same cases, his rifle, same factory load) .

Should I use the same approach, and size his cases down -.003 less (to
.005)? I have heard that the Rem autos are picky, and small base dies are recommended, etc.

Should I take the cases down more to account for this
You should size his cases with a small base die, there are plenty of those, and you should use a calibrated case gage and size to gage minimum.

I use Wilson gages, they are cheap and the dimensions from the lower ledge and upper ledge correspond exactly with chamber headspace gages.

I don’t know what the RCBS precision mike measures, there are a bunch of “relative” gages that are not calibrated to anything.

Your bud’s cases are long because they were fired and ejected from a semi auto. Cases get stretched because cases are extracted while there is still pressure in the barrel.

So you heard this two times now. Believe it yet?

You size those cases long and your bud may have an out of battery slamfire.

Happens even in commercial rifles.

Browning Automatic Rifle (BAR) Slamfire in 270 Win. Neck sized cases.

It's good to think you had the good common horse sense to ask that question. Some have assumed nothing is any different since the cartridge is what it is, 30-06 or what ever high powered rifle round, and then necked it as with their bolt actions. A man came into the gun shot I worked in with a really nice, well was a really nice Browning semi auto, I think it was chambered in 270 win., no matter. He said he had been necking for a while for that rifle without problems. I doubt he considered now and then chambering issues as problems. Either way, all it took was one slam fire to ruin his day and rifle, and fortunately not his life!
If I'm not shooting, I'm reloading.

Last edited by Slamfire; November 9, 2011 at 05:06 PM.
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