Post by curlymaple42 on Jun 3, 2011 9:50:46 GMT -8
OK, I just finished three 264lbc-ar builds. Went to the range today with two of them and am noticing pressure signs. Namely, flattened primers and brass smears near the base of the case where the extractor is. Here are the specs on ammo and the two builds I shot today:
#1 Mega billet upper 18" BHW 264lbc-ar barrel midlength gas port. bolt from BHW railed gas block (ie not adjustable) Carbine buffer system Stock AR trigger group
#2 A2 upper 18" BHW 264lbc-ar barrel midlength gas port bolt from BHW PRI adjustable gas block rifle buffer system Mega skeleton trigger (love it by the way!)
On #2 I adjusted the gas system down so it did not cycle, then tuned it back up until it just cycled the ammo. On that gun I actually had a couple primers back out a little. There are brass smears on the bolt face too. Here are the ammo specs:
Hornady 123 Amax factory 6.5Grendel ammo
Handloads: 120gr Berger Match Tactical bullets, Lapua 6.5G brass, 30gr BL-C2 powder which is on the lower end of the scale.
Oh, I had a receiver face truing tool made to make sure the faces of the receivers were perfectly square which has been reported as being an issue possibly in higher pressure AR calibers. They needed a little truing, but not much.
Post by toolsofthetrade on Jun 3, 2011 13:20:41 GMT -8
My upper is currently at BHW with Carl working on it, having same issue, hopefully they get this figured out. I have been talking with carl as recently as yesterday, he is eliminatng variables trying to get to the root cause. I personally am wondering now with youre two as well, if it is a bore diameter issue, or chamber dimension issue, but I will await the verdict of those more knowledgable than myself. I have a hunt coming up soon and still have to do load developement......hope it gets resolved soon.
Post by curlymaple42 on Jun 6, 2011 4:21:55 GMT -8
Used some Hornady 123grAmax factory ammo. I was using factory data from 6.5G for that particular bullet. I never had problems with 120grSMK's and I think I have some of those left, so maybe I will try a few of those.
The third gun has not been shot yet but it is the same as mine with the adjustable gas system.
Post by thesilent1 on Jun 11, 2011 19:31:19 GMT -8
Which of the two types of ammo was causing the pressure signs? Did you get it from both types or just one of them?
Glad that Carl is looking into this issue for you. Double check your reloading data-sometimes there are typos that can cause big mistakes with handloads. Also, please post whatever you discover was causing the problem, so that the rest of us can learn what to watch out for? Thanks and good luck
Post by guncollector on Jun 23, 2011 0:18:37 GMT -8
The Alexander Arms reloading data that I have shows 30 grains of Blc2 to be the max load with the Berger 120 gr. Match Tactical bullet. I have had similar pressure signs in Alexander Arms barrel with Blc2.
Retired law enforcement officer and law enforcement firearms instructor.