Overpressure?

S

snox801

Well-Known Member
Joined
Sep 19, 2012
Messages
5,287
Location
Spring Lake Michigan
Ok guys full story.
I have a 16" bolt 6.5 grendel, and a 18" 6.5 grendel.
Both setup as point and shoot max point blank range funds for thermals.
Anyway. When hammer cut the 99gr I did load work with those and xbr powder. Both showed pressure at the same time. Also the same spot as my brothers two grendels. Fast forward to the 97 absolute.
I couldn't get enough powder in the case with xbr to get any more speed so after looking rl10 looked like a winner. Faster burn rate and much less case fill allows more room for powder. Worked up a load in the 16" bolt and made it to just shy of 3k FPS.
Went to my ar and can't get any more speed than the 99 without creating a belt like rim at base of case. I can't even get to the same speed or charge as Barnes has in for the 100gr.
No flat primer no brass flow nothing else for pressure. I've determined it seems to be opening the bolt to early is all I can figure. I'm gonna do a adjustable gas block and hope this helps. Am I'm heading in the right direction?
 
snox801 said:
Ok guys full story.
I have a 16" bolt 6.5 grendel, and a 18" 6.5 grendel.
Both setup as point and shoot max point blank range funds for thermals.
Anyway. When hammer cut the 99gr I did load work with those and xbr powder. Both showed pressure at the same time. Also the same spot as my brothers two grendels. Fast forward to the 97 absolute.
I couldn't get enough powder in the case with xbr to get any more speed so after looking rl10 looked like a winner. Faster burn rate and much less case fill allows more room for powder. Worked up a load in the 16" bolt and made it to just shy of 3k FPS.
Went to my ar and can't get any more speed than the 99 without creating a belt like rim at base of case. I can't even get to the same speed or charge as Barnes has in for the 100gr.
No flat primer no brass flow nothing else for pressure. I've determined it seems to be opening the bolt to early is all I can figure. I'm gonna do a adjustable gas block and hope this helps. Am I'm heading in the right direction?
Click to expand...
You can go it many ways! Heavier buffer, stronger spring and/or adjustable gb. An adjustable buffer is also possible. Was it a build gun or bought complete (at least a complete upper)? Having 556 and 300bo used without any adjustable gb with 0 issues, I do use the adjustable kind for all other ar15 cartridges. Making sure the gb is centered over the port is a must, because without it will give false signs (early op signs). Odin and SI make adjustable buffers in both lite and heavy. Springco makes several spring weights (I think 5) for the ar15.
 
snox801 said:
Superlative arms on the recommendation of Texas mike. I've never had issues with needing one with any of my other ar's and hand load them all but like I said I have been very lucky.
Click to expand...

good good. i run one of those on my 6.8. actually it was a first production run one and he originally came out with. did a revision or found an issue with them and had me to send it in to him for his fix. on top of that he paid to and from shipping. good folks and a good AGB.
 

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