Need Chamber Recommendation For 308 AR Type Rifle

[jm5546]

I need some help....

I am in the process of building a .308, AR-10 style (DPMS Pattern), high precision bench rifle, utilizing a 20" Kreiger S.S. barrel, with a 1-11.25 twist. I need help in identifying a chamber/reamer that will maximize the rifle's accuracy potential (i.e. consistent <0.5" MOA). Although I will be handloading, I want to optimize the chamber/rifle for Federal 168gr SMK GMM factory ammunition. If possible (a secondary requirement), I would also like it to achieve the same accuracy using Federal 175 SMK GMM ammo.

In researching chamber reamers, I found numerous recommendations (95 Palma, Modified Palma, 2011 Full Bore, Bisley, Obermeyer 3 deg, Obermeyer 5 deg, and 308 match). Although not clearly stated, it appeared that these recommendations were specific to bolt guns.

Concerned (maybe incorrectly) that a semi-automatic will require a bit more clearance for reliable operation, I am hesitant to hang my hat on any of these recommendations. That said….Does anyone have experience with a similar build that can relate their achieved accuracy and/or a chamber/reamer recommendation?

Thank you

 

[powderBurnz]

Re: Need Chamber Recommendation For 308 AR Type Rifle

I went with a Krieger M110 barrel, 1-11.25tw, Obermeyer chamber. It doesnt like 155gr Scenars. It doesn't like being dirty. But it shoots 175SMKs and 190SMKs like a dream. It was doing decent out at 800-1000yds, I just need to hop-up the loads a bit. I have a bunch of 168SMks but haven't run em yet.

 

[Rprecision]

Re: Need Chamber Recommendation For 308 AR Type Rifle

Dave Kiff at Pacific Tool and Gauge is awesome. On my .308 build I told him what I wanted to do, what bullets, use, Etc. and he ground a reamer up.

 

[Armorer59]

Re: Need Chamber Recommendation For 308 AR Type Rifle

First off, I'm new here so howdy! Some things for consideration. Accuracy potential for any chambering will be directly affected by cartridge to chamber clearance. The more clearance the less accurate the firearms tends to be. If you reload, you can some what taylor your loads to fit the given chambering. Whether you reload or not, I would recommend cartridge headspace gages to measure your loaded ammo. Keep in mind that SAAMI dimensions on .308 are min 1.6305" to 1.634" max on headspace gages.

When I build a match M1A, I use a match pull through chamber reamer and match headspace gages and stay on the smaller side of the dims. I've found this helps reduce case growth during firing. As for trying to get 2 different loads to shoot equally well, you may or may not be able to achieve that. May have to settle on a happy medium between the two. Hope this helps.

 

[branson1369]

Re: Need Chamber Recommendation For 308 AR Type Rifle

I had Jim Ruiz @ Predator CUstom do my personal barrel and 12 more for my customers. The balnks were Rock Creek 5R 1:11.25 and all are meeting your desired accuracy if the shooter does thier job. All of these barrels are in Mega MA-TENS I sold on a variety of group buys.

Happy to share any details with you and a good ref. sheet I have that folks have found helpful

Semper Fi