308 80% AR bolt catch won't work

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[ARCHIVED THREAD] - 308 80% AR bolt catch won't work

Posted: 5/11/2015 5:48:52 PM EDT

So I took my finished 80% polymer80 fitted with DPMS sportical upper to the range to function test it (it had no sight so I could only fire a couple of rounds). I noticed the bolt catch won't work (I loaded one round into the mag to function test, then loaded two to make sure it cycles properly). When I place the empty mag into the gun and pull the charging handle, the bolt catch works but if I put a round in the mag, fire it, the bolt catch for some reason failed to work. Can anyone tell me if it's the mag or the bolt catch?

Posted: 5/11/2015 6:06:07 PM EDT

[#1]

try another mag, that would eliminate that

Posted: 5/13/2015 1:37:50 PM EDT

[#2]

AR-15 bolt hold-open latches won't work in AR-10 or DPMS .308 lowers. Make sure you have the right sized mag catch.

Posted: 5/13/2015 1:51:19 PM EDT

[#3]

Quoted:
So I took my finished 80% polymer80 fitted with DPMS sportical upper to the range to function test it (it had no sight so I could only fire a couple of rounds). I noticed the bolt catch won't work (I loaded one round into the mag to function test, then loaded two to make sure it cycles properly). When I place the empty mag into the gun and pull the charging handle, the bolt catch works but if I put a round in the mag, fire it, the bolt catch for some reason failed to work. Can anyone tell me if it's the mag or the bolt catch?

View Quote

it sounds like its short stroking . you should check that the gas block is in good alignment with the gas port and check for gas leaks at the gas block to barrel and gas tube to block as well as gaskey to carrier

Posted: 5/13/2015 4:40:25 PM EDT

[#4]

Shotgun the upper open and insert a empty mag.
Pay close attention to the mag catch tab against the back of the mag follower, and make sure that the empty mag follower raised the mag catch all the way up.

Now pull the mag, lock the upper back down, and pull the charging handle all the way back. Play close attention to the last inch'ish of the handle pull to make sure that the tension needed to pull the handle all the way does not increase from about the half way back pull point of the handle. If the handle tension increases for the last inch'ish of the pull, then either you have tail wedging, or the wrong recoil spring is play that is coil binding up.

Now insert the mag again, and pull the charging handle all the way back, and the face of the bolt should clear the back of the catch by about 1/4" of a inch.

As for distant of the face of the bolt in front of the back of ejection port on a 308, If you upper does not have a dust cover, then the face of the bolt should be flush, while if your upper does have ejection port dust cover, then the face of the bolt should stop about 1/8" to 1/4" in front of the back of ejection port window.

Now weeding all this out, before you shot/test the rifle again under live fire, make sure to clean the chamber with a chamber brush and CLP, and the upper receiver bearing areas have been CLP lubed as well.

Still having problems, the suspect either a gas issue (leaking or blocked), or you have a binding issue instead.

Posted: 5/14/2015 10:41:29 PM EDT

[#5]

I just tried it.

Tension does not increase at all through the range of the pull, and the bolt clears the bolt catch at least 1/4". The gas system is properly aligned and fitted... it was built by DPMS anyways.

All I can think of is perhaps the ammo was weak? I used perfecta 308 I bought from Walmart...

I coated the bolt carrier with a fair amount of CLP to see if lack of lube is the problem...

Posted: 5/15/2015 3:23:48 PM EDT

[#6]

Try some 308 white box win ball type ammo and see if you have the same problem.

Posted: 5/18/2015 8:56:13 PM EDT

[#7]

I'm thinking the rifle is short stroking.

Basically I tried again. When I load one round into the magazine, the bolt locks back properly (not always). But sometimes (about once every 10 rounds) I'd get a stovepipe. I do not know if it's bad magazine because the magazine doesn't seem to do a good job of holding the round. I've had rounds fly off the mag when I try to pack it (the round wasn't seating properly all the time).

On the other hand I was sighting in the UTG red dot sight I got (I needed a cheap sight while I save up for a good scope). It's not a precision shooting instrument, but I could get 2" groups at 50 yards. I think it's more me than the sight honestly (I couldn't get a vise to test it).

The primer has very slight cratering and some have minor extractor marks... I wonder if this is cause for concern (rough chamber or something)

Another thing is, the upper has carbine length gas system but I'm using rifle length buffers (standard AR10 buffer spring/stock). Do you think that could be the problem?

[ARCHIVED THREAD] - 308 80% AR bolt catch won't work

AR-15 » Troubleshooting

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