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ionion
10-11-2012, 2:24 PM
So i just put together a brand new AR (Adams arms evo ultra light weight upper with NFA poly lower) and went to test it today. When shooting a "full" cali legal pmag (lols full - sorry couldn't help myself) the BCG stays open while there are still rounds in the mag. I have tried this with 3 different pmags and the problem seems to come and go. Is this just the break in period of a never fired AR? the problem occurred much less at the 250ish round count. If it matters PMC bronze was used. Thanks

Munny$hot
10-11-2012, 2:28 PM
As in the bolt locks open and you have to hit the bolt hold open release to charge the weapon again? If so did you forget to install the bolt hold open spring/detent?

ionion
10-11-2012, 2:33 PM
Yes the bolt holds open and i have to press the release to chamber another round. the lower I got was complete lower.... so maybe missing parts?

FeuerFrei
10-11-2012, 2:40 PM
Swap lower with a buddy and test again.
If them problem follows the lower then you'll know.
I have seen issues with regard to the lower parts not being... correct. Reciever okay but not the guts.
PMC Bronze is also on the weak side. Gas regulator set to wide open on this stuff.

Munny$hot
10-11-2012, 3:24 PM
push on the very bottom of the bolt release. It should spring back when released

myk
10-11-2012, 3:31 PM
push on the very bottom of the bolt release. It should spring back when released

As long as there are more rounds left in the 'mag the rifle the bolt should be springing back on its own...

Dinosaur Jr
10-11-2012, 6:56 PM
Poly lower maybe a bad choice?

wash
10-11-2012, 7:12 PM
I think there was a bad batch of pmags out there.

After permanently modifying them for 10 round capacity, I doubt the person doing the work thought a warranty exchange was a very good idea. I bet there are a bunch of bad magazines out there for that reason.

First thing, try an aluminum or steel magazine like a D&H, C Products, etc.

If those still activate the BHO while you still have ammo in the magazine, carefully look to see what is pushing up on the BHO.

As others have said, the BHO is spring loaded, with no magazine in the lower it should be easy to tell if that is the case because the BHO will be pushed down by it's spring. If it moves freely you might be missing a spring but I think that is unlikely.

Magazines are my first guess.

ExtremeX
10-11-2012, 7:15 PM
I agree with wash... try a new/different magazine first and see if that resolves your problem.

tiller
10-11-2012, 7:21 PM
Poly lower maybe a bad choice?

plastic parts in a full metal gun are never good?!

ExtremeX
10-11-2012, 7:25 PM
plastic parts in a full metal gun are never good?!

While I don’t particularly care for polymer lowers, there are plenty of people using them with success…

I doubt this is the root of the problem unless something is out of spec in the manufacturing process, or the LPK was not installed correctly.

AlliedArmory
10-11-2012, 7:31 PM
Try a different brand of magazine. If that doesn't work maybe try someone elses lower to try.

ionion
10-11-2012, 7:31 PM
We tried the pmags with just the lower to see if there was anything catching, it seemed pretty impossible for the BHO to catch on something unless the magazine follower is all the way at the top of the mag.

wash
10-11-2012, 7:49 PM
Well something is pushing the BHO up when the spring should be holding it down.

You just have to figure out what that is.

Black Star Tactical
10-17-2012, 11:17 AM
We have put together at least 200+ 16" M4 type carbines using the NFA LW-15 Polymer lowers and have found two factors which will cause the problem you are having.
1. The buffer and springs which come installed on the LW-15 are designed to cycle the higher pressure 556 NATO round. We test fire ours with the same 223 ammo you are using to ensure that they operate properly with the lower pressure round which most of our customers shoot.
2. We have had customers return rifles describing your problem only to find that they operate just as they did when we shipped them. We were only able to get them to lock the BCG back by "soft shouldering" them which absorbs the recoil and keeps the bolt from traveling all the way to the rear AKA "short Stroking" and then engages the BHO. We remedied these by replacing the buffer spring with a lighter one from UTG (part#RB-T6BM-50) problem solved
Of course your upper may possibly be contributing but we'll assume you have the gas selector in the right position, but try placing the butt stock against a stationary object like a tree or fence post, while aiming at a safe target area and fire. If it cycles without locking the bolt back, you are probably holding it too loosely when you fire normally. If it continues to malfunction, try a lighter buffer spring

bob7122
10-17-2012, 11:32 AM
have you checked to see if the flux capacitor is inserted correctly on the p-mag? usually with mags modified to 10 rounds, people forget to straighten the flux capacitor.

bob7122
10-17-2012, 11:48 AM
We have put together at least 200+ 16" M4 type carbines using the NFA LW-15 Polymer lowers and have found two factors which will cause the problem you are having.
1. The buffer and springs which come installed on the LW-15 are designed to cycle the higher pressure 556 NATO round. We test fire ours with the same 223 ammo you are using to ensure that they operate properly with the lower pressure round which most of our customers shoot.
2. We have had customers return rifles describing your problem only to find that they operate just as they did when we shipped them. We were only able to get them to lock the BCG back by "soft shouldering" them which absorbs the recoil and keeps the bolt from traveling all the way to the rear AKA "short Stroking" and then engages the BHO. We remedied these by replacing the buffer spring with a lighter one from UTG (part#RB-T6BM-50) problem solved
Of course your upper may possibly be contributing but we'll assume you have the gas selector in the right position, but try placing the butt stock against a stationary object like a tree or fence post, while aiming at a safe target area and fire. If it cycles without locking the bolt back, you are probably holding it too loosely when you fire normally. If it continues to malfunction, try a lighter buffer spring

check this out OP

Jet Setter
10-17-2012, 12:07 PM
Poly lower maybe a bad choice?

I use my NFA LW-15 on my RRA ATH upper and have yet to have a problem. It has been a great lower so far.

bob7122
10-17-2012, 6:19 PM
I use my NFA LW-15 on my RRA ATH upper and have yet to have a problem. It has been a great lower so far.

me too. and it has not failed me yet with either .22lr or 556 ammo.

ionion
10-17-2012, 7:22 PM
We have put together at least 200+ 16" M4 type carbines using the NFA LW-15 Polymer lowers and have found two factors which will cause the problem you are having.
1. The buffer and springs which come installed on the LW-15 are designed to cycle the higher pressure 556 NATO round. We test fire ours with the same 223 ammo you are using to ensure that they operate properly with the lower pressure round which most of our customers shoot.
2. We have had customers return rifles describing your problem only to find that they operate just as they did when we shipped them. We were only able to get them to lock the BCG back by "soft shouldering" them which absorbs the recoil and keeps the bolt from traveling all the way to the rear AKA "short Stroking" and then engages the BHO. We remedied these by replacing the buffer spring with a lighter one from UTG (part#RB-T6BM-50) problem solved
Of course your upper may possibly be contributing but we'll assume you have the gas selector in the right position, but try placing the butt stock against a stationary object like a tree or fence post, while aiming at a safe target area and fire. If it cycles without locking the bolt back, you are probably holding it too loosely when you fire normally. If it continues to malfunction, try a lighter buffer spring

anyone know where i can get the spring by itself? or a similar spec spring?

BrassCase
10-17-2012, 7:59 PM
Similar problem with my Larue. They told me to use 62 gr. ammo for the first 300 or so rounds. I had problems out of my PMAG as well and ASC mags too.