308 tight chamber vs. brass life ?

[Digger]

Here's a question gentlemen ....
finally succeeded in getting my AR-10 to function ... turns out it has a tight chamber .
Up to now been using a standard full length sizer , been happy camper in both my M1 receiver and Ruger bolt until I tried the same rounds in the AR ..
No go , would jam on occasion , even with Military surplus ...
Went to a small base die and polished the chamber and ....YES !! , it loves the ammo now , no problem.
Now with that said , can I use the small based sized ammo with out fear as far as expansion in the M1 chamber ?
knowing that it is incrementally bigger ... as far as brass life ?
The Ruger bolt I am not to worried about ...
Will be annealing when I can but ...
any input would be appreciated much
digger

[sawinredneck]

I'm not a benchrest shooter, s I may very well be corrected. But as I understand it most FL size for semi-autos, but just bump the neck back for better accuracy in bolt guns. I don't believe it has anything to do with case life.

[BK7saum]

Is the chamber tight on the case walls requiring the SB sizer or is your FL sizer just a bit too deep?

Do you have a way to get a headspace measurement to compare the shoulder bump between fired cases in your rifles? That would tell you what variance you're dealing with. If only a couple thousandths different between rifles, them load for tightest and shoot away. If more than 0.003, I'd segregate my brass for each rifle.

I FL size on every reload for consistency and only bump the shoulder 0.001"

If you can measure or mark a case and see where it's tight, that'd help. You may be able to trim a shell holder or die and get the cases to chamber. I've had to trim more than one FL Die

[StratsMan]

A case gauge will tell you how close your original FL die is to spec... You may see the difference between the FL and Small Base, too...

[ole 5 hole group]

Could maybe consider a couple other options. A body die might solve your problem and maybe setting up your FL sizing die to cam-over might just give that little extra. Camming-over with my Redding FL sizer solved my 30-06 problem in my BAR; your mileage may vary.

[308Jeff]

My DMPS AR-10 also has a tight chamber, requiring a small base die as well.

I don't plan on getting more than 3-5 firings, but I have more 308 brass than I could ever consume in my lifetime.

[EDG]

You talk about chamber sizes but you have no data - no numbers.

So to tell you the real story take 4 or 5 fired cases from each chamber and keep them separated.

measure the following with a good micrometer and record the data

1. Diameter of the fired cases at the shoulder (about .030 below the corner on the body so you are not on the shoulder radius)
2. Measure the body diameter at .200 above the case head at the pressure ring.
3. Measure the case lengths from the case head to the shoulder datum if you have a gage to do this.

Those numbers will permit you to compare one chamber to another.

You can get a SAAMI chamber drawing and compare to #1 and #2.

[Digger]

Thank you so much gentlemen ...
great words of advice to go by , have been using a wilson 308 gauge all this time but still surprised me with the 10 chamber ...
will go by your tidbits of advice , only on this site can i get such great help.
thank you
digger