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Posted: 8/24/2015 2:30:05 PM EDT
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I built a 308 AR with the intention of it being a nice DMR gun capable to 1000 yds. I have run it in 2 precision rifle classes with less than optimal results.
Most significantly, I am piercing primers. Over the weekend, after 1 ring at 1k, the bolt locked up due to a collection of primer bits in the bolt. I had been checking brass early on and noticed that the primers were "flowing", but no piercing. Apparently as the shooting continued (approx 200 rds), I started getting piercing. This was with Fed ADXM 118BL, This also happen regularly with FGMM 168, to the point that I quit using them. I have not seen this happen with surplus 147 ball. Specs: DPMS upper and lower Rainier Ultramatch 18" barrel DPMS chrome BCG and AIM NIBx BCG (have had the headspace checked and was told its good) Jard trigger Magpul ACSL stock Vortex Viper PST 4-16 FFP MIL YHM Phantom TI suppressor Any thoughts on why I am running into this issue and what I can do to correct it?  " />
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Firing pin aperture and pin are too large. Need to go .068" or smaller. You have a .080" right now, or thereabouts.
This is a big problem with any high pressure cartridge in the .308 guns, especially ones that push longer bearing surface pills with slower burning powders. I've pierced a lot of .260 Rem primers, or made them flow like yours. |
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Quoted:
Thanks for the feedback guys. Been around ARs for a while, but first I have heard of different aperature and firing pin diameters. After a quick googling, it seems that Armalite is the only one with the smaller diameter. Are there other options? JP makes a DPMS-compatible high pressure bolt and firing pin. |
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Quoted:
I built a 308 AR with the intention of it being a nice DMR gun capable to 1000 yds. I have run it in 2 precision rifle classes with less than optimal results. Most significantly, I am piercing primers. Over the weekend, after 1 ring at 1k, the bolt locked up due to a collection of primer bits in the bolt. I had been checking brass early on and noticed that the primers were "flowing", but no piercing. Apparently as the shooting continued (approx 200 rds), I started getting piercing. This was with Fed ADXM 118BL, This also happen regularly with FGMM 168, to the point that I quit using them. I have not seen this happen with surplus 147 ball. Specs: DPMS upper and lower Rainier Ultramatch 18" barrel DPMS chrome BCG and AIM NIBx BCG (have had the headspace checked and was told its good) Jard trigger Magpul ACSL stock Vortex Viper PST 4-16 FFP MIL YHM Phantom TI suppressor Any thoughts on why I am running into this issue and what I can do to correct it? http://<a href=http://i1131.photobucket.com/albums/m546/triharder72/Mobile%20Uploads/20150824_135244.jpg</a>" /> This might help, I had the same issue http://www.ar15.com/forums/t_3_121/678890_.html&page=1 |
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