Issues with new AR10 build

[graydog1]

Good day all
I have an AR10 build with all new parts DPMS lower, upper, LPK and BCG, YHM railed gas block, free float rail and flash hider, Rainier 16inch chrome lined heavy barrel, slash heavy buffer with modified spring, Magpul commercial ACS stock, Bravo co bolt upgrade kit. Using DPMS C-Products and Magpul magazines with Winchester USA and PMC factory ammo.
Problem is that the damn rifle MUST be almost dripping with lube to run right. If my BCG isn;t sloppy wet I get FTE stoppages after almost every round. Went to the range and the well lubed beast ripped off two magazines no issues. let it sit for a couple hours while doing some bolt gun work then the jam-o-matic returned. Any suggestions besides the obvious??
:help::help:

[High Tower]

What mags are you using? That might be a problem.

The bolt might be a problem too.

I have no experience with Ranier, but the gas port might be too big? Port not lined up with gas block?

Or buffer might not be right for the build.

Those are the things that come to my mind. Or ammo.

[graydog1]

Runs fine with all magazine and ammo combos when well lubed, otherwise it's extraction/ejection issues. Only about 400 rounds thru this rifle so far

[matemike]

Not positive on how a 7.62 bolt works, but if it's like a 5.56, check the extractor spring. Maybe add a rubber spring insert or rubber o-ring over the extractor spring.

Is the bolt locking back on every last round fired? I ask so you could rule out short or slow stroking.

[High Tower]

Runs fine with all magazine and ammo combos when well lubed, otherwise it's extraction/ejection issues. Only about 400 rounds thru this rifle so far

Gotcha. Honestly, I would buy a new bolt or entire bcg from LMT.

Edit to add: I would suggest doing this regardless. Also, try some hotter ammo.

[Suwannee Tim]

Check the fit of the cartridge rim under the extractor. Remove the BCG and put the rim of a cartridge under the extractor in the reverse of the motion of ejection. If the extractor is too tight it will bind the rim as the ejector tries to kick it out. If this is so you can free it up by putting a tiny amount of abrasive compound under the rim of a cartridge and using it to lap the extractor taking care not to lap the bolt face.

[RD62]

Gotcha. Honestly, I would buy a new bolt or entire bcg from LMT.

Edit to add: I would suggest doing this regardless. Also, try some hotter ammo.

Good luck with that.

I have never seen a .308 LMT BCG out in the wild (not saying they aren't there, but would be considerably rare).

LMT is having trouble keeping up with complete rifle orders. To my knowledge the only .308 parts they have out are barrels.

[RD62]

Good day all
I have an AR10 build with all new parts DPMS lower, upper, LPK and BCG, YHM railed gas block, free float rail and flash hider, Rainier 16inch chrome lined heavy barrel, slash heavy buffer with modified spring, Magpul commercial ACS stock, Bravo co bolt upgrade kit. Using DPMS C-Products and Magpul magazines with Winchester USA and PMC factory ammo.
Problem is that the damn rifle MUST be almost dripping with lube to run right. If my BCG isn;t sloppy wet I get FTE stoppages after almost every round. Went to the range and the well lubed beast ripped off two magazines no issues. let it sit for a couple hours while doing some bolt gun work then the jam-o-matic returned. Any suggestions besides the obvious??
:help::help:

Can you be more specific in the nature of your FTE stoppages? Failure to extract or failure to eject? Spent casing in the chamber and the bolt trying to feed a live round? Bolt not cycling? What?

[Singlestack Wonder]

Sounds like it is "under gassed" (i.e. low gas pressure). Typically 308/7.62 AR's are way overgassed. In my opinion, I would check the alignment of the gas hole on the gas block to the gas hole on the barrel. Also, what type of ammo are you using? A number of soviet block country rifle ammo offerings in 5.56 and 7.62 are underpowered.

Good luck!

[High Tower]

Good luck with that.

I have never seen a .308 LMT BCG out in the wild (not saying they aren't there, but would be considerably rare).

LMT is having trouble keeping up with complete rifle orders. To my knowledge the only .308 parts they have out are barrels.

You speak the truth. Best to get in line early in this case.

This is also why I've never attempted a .308 build. There is a lack of high quality parts readily available and fewer stores that stock them.

[Todd.K]

Because AR type 308/7.62 rifles are not all the same like 223/5.56 rifles, you should not call it an AR-10 unless it is Armalite pattern.


What length receiver extension and buffer did you use?

What action spring, and why is it modified?

What length gas system does the barrel use?