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I built an LR-308 on a CMMG lower. I got the complete upper from Midway, put it on the CMMG lower with an A2 stock (the regular non-collapsable stock) with standard buffer tube. I used the buffer and spring that is SUPPOSED to be the correct one for an LR-308. The upper is a 24 inch stainless steel bull barrel, flat top, no ejection port cover, no forward assist. I also installed a JARD 2 pound single stage trigger.
So I took it to the range to test and sight in the scope. I first loaded a single round in the MAGPUL magazine, in case the trigger caused a double fire or fully auto. Rifle shot fine. Then I loaded 2 rounds, shot fine again. Then loaded 10 rounds and shot one more to finish a group, shot fine. I adjusted the scope and started shooting again but the rifle would jam every 2-4 rounds. It was always a failure to feed that caused the jam. I would find a round partially stripped from the magazine but not properly fed into the chamber. The rifle always ejected properly and every chambered round fired properly.
When I look at a cartridge that didn't feed properly it looks like it got scraped by the bolt rather then pushed by the bolt. The side of the cartridge that was next to the bolt is badly scratched, sometimes even dented, but the bolt is on top of the cartridge rather than behind it as it should be. If I manually cycle the bolt it always feeds fine, it only has trouble when the gas system is cycling the bolt.
As many people have said about the DPMS upper, it seems very tight. The bolt head is much harder to turn in the bolt carrier than the one in my new Rock River .223 upper. The bolt carrier on the LR-308 doesn't hang up anywhere when I cycle it manually but it moves with much more friction than the one on my Rock River.
So my questions are these: Is it possible that excessive friction on a new LR-308 would cause the gas system to not push the bolt carrier all the way back, and therefor not properly pick up the next cartridge? Would having the wrong buffer or spring (as in I possibly have a buffer and/or buffer spring from an AR-15) cause the bolt carrier to not go all the way back? How would I know if I have the wrong buffer or spring? If the cause of the incomplete cycling is due to excessive friction will that get better over time? Am I completely on the wrong track here? Could the problem just be a few lousy magazines?
One last thing. I tried three different kinds of ammo: Some mil surplus 150 grain (I believe it is Prvi Partizan), some Federal 168 grain Match ammo (says on the box that it is good for M1A) and some Prvi Partizan 168 grain hollow point boat tail match ammo. All of these had the same issue, failure to feed with the bolt laying on top of the un-fed cartridge.
So I took it to the range to test and sight in the scope. I first loaded a single round in the MAGPUL magazine, in case the trigger caused a double fire or fully auto. Rifle shot fine. Then I loaded 2 rounds, shot fine again. Then loaded 10 rounds and shot one more to finish a group, shot fine. I adjusted the scope and started shooting again but the rifle would jam every 2-4 rounds. It was always a failure to feed that caused the jam. I would find a round partially stripped from the magazine but not properly fed into the chamber. The rifle always ejected properly and every chambered round fired properly.
When I look at a cartridge that didn't feed properly it looks like it got scraped by the bolt rather then pushed by the bolt. The side of the cartridge that was next to the bolt is badly scratched, sometimes even dented, but the bolt is on top of the cartridge rather than behind it as it should be. If I manually cycle the bolt it always feeds fine, it only has trouble when the gas system is cycling the bolt.
As many people have said about the DPMS upper, it seems very tight. The bolt head is much harder to turn in the bolt carrier than the one in my new Rock River .223 upper. The bolt carrier on the LR-308 doesn't hang up anywhere when I cycle it manually but it moves with much more friction than the one on my Rock River.
So my questions are these: Is it possible that excessive friction on a new LR-308 would cause the gas system to not push the bolt carrier all the way back, and therefor not properly pick up the next cartridge? Would having the wrong buffer or spring (as in I possibly have a buffer and/or buffer spring from an AR-15) cause the bolt carrier to not go all the way back? How would I know if I have the wrong buffer or spring? If the cause of the incomplete cycling is due to excessive friction will that get better over time? Am I completely on the wrong track here? Could the problem just be a few lousy magazines?
One last thing. I tried three different kinds of ammo: Some mil surplus 150 grain (I believe it is Prvi Partizan), some Federal 168 grain Match ammo (says on the box that it is good for M1A) and some Prvi Partizan 168 grain hollow point boat tail match ammo. All of these had the same issue, failure to feed with the bolt laying on top of the un-fed cartridge.
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