Help with AR BCG getting stuck

[PhillipeC]

So I just built a lower and when going to cycle and make sure everything works, it cycles fine, I can dry fire but then when I charge the bolt again with trigger pressed, when I release for bolt to go into battery and trigger reset, it returns "slowly" as it's getting stuck somewhere and dragging. When trigger is not pressed, it cycles fine with no dragging. It is all Mil-Spec.

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[JuglansRegia]

Sounds like you didn't assemble your fire control kit properly, unless its a cassette type.

 

[PhillipeC]

Sounds like you didn't assemble your fire control kit properly, unless its a cassette type.

I will double check but I'm almost 100% sure I did. I put a couple of them together this evening and the other one worked fine.

 

[Barfly]

Well, if you're pulling the trigger, is the hammer spring pushing the hammer up into the carrier, creating drag?

 

[PhillipeC]

Well, if you're pulling the trigger, is the hammer spring pushing the hammer up into the carrier, creating drag?

That is what I think is happening but I have never experienced it before and I've done several builds. Some you can feel the drag but it is just a matter of breaking it in and even though there is some drag, this one actually slows down the bolt returning to battery.

 

[v0lcom13sn0w]

ALL uppers and lowers i build go thru a break in process that includes soaking the internals with rem oil or CLP and then racking the charging handle about 200 times. about 1/4 way thru a 'grey metallic slurry" forms and essentially hones out any casting flash or any excessive coating/material on the internals.when done, i clean it very thoroughly and re-lube with a proper amount of oil. usually smooth as glass after that.

assuming everything is in spec and the trigger springs are installed correctly, id try that. i have had 1 too long gas tube that would prevent a bolt from going into battery and 1 bent gas tube slowing the bolt down as it would align with the gas key.

edit: to add to that, on real stubborn/budget builds with low QC ive even used oil and valve lapping compound to fix high spots/ poor casting

 

[gryghin]

ALL uppers and lowers i build go thru a break in process that includes soaking the internals with rem oil or CLP and then racking the charging handle about 200 times. about 1/4 way thru a 'grey metallic slurry" forms and essentially hones out any casting flash or any excessive coating/material on the internals.when done, i clean it very thoroughly and re-lube with a proper amount of oil. usually smooth as glass after that.

assuming everything is in spec and the trigger springs are installed correctly, id try that. i have had 1 too long gas tube that would prevent a bolt from going into battery and 1 bent gas tube slowing the bolt down as it would align with the gas key.

edit: to add to that, on real stubborn/budget builds with low QC ive even used oil and valve lapping compound to fix high spots/ poor casting

This...

This is the Way...

 

[PhillipeC]

ALL uppers and lowers i build go thru a break in process that includes soaking the internals with rem oil or CLP and then racking the charging handle about 200 times. about 1/4 way thru a 'grey metallic slurry" forms and essentially hones out any casting flash or any excessive coating/material on the internals.when done, i clean it very thoroughly and re-lube with a proper amount of oil. usually smooth as glass after that.

assuming everything is in spec and the trigger springs are installed correctly, id try that. i have had 1 too long gas tube that would prevent a bolt from going into battery and 1 bent gas tube slowing the bolt down as it would align with the gas key.

edit: to add to that, on real stubborn/budget builds with low QC ive even used oil and valve lapping compound to fix high spots/ poor casting

I'll try that today. Thanks for the input!

 

[Member 34319]

This may be shocking to some to hear. But the trigger is part of the recoil operations. The bolt is slowed by it as the bolt must reset it in its rearward travel. A heavy spring in a trigger can actually cause enough drag to cause the action to have malfunctions.

It can be as simple as an installation error, or as unnoticeable as a slightly off spec part.

Being that you are manually cycling the action and feeling this, not shooting the gun and seeing it operate, I'd say you are in need of some actual live fire. Stop playing with it and go shoot it.

 

[PhillipeC]

This may be shocking to some to hear. But the trigger is part of the recoil operations. The bolt is slowed by it as the bolt must reset it in its rearward travel. A heavy spring in a trigger can actually cause enough drag to cause the action to have malfunctions.

It can be as simple as an installation error, or as unnoticeable as a slightly off spec part.

Being that you are manually cycling the action and feeling this, not shooting the gun and seeing it operate, I'd say you are in need of some actual live fire. Stop playing with it and go shoot it.

I'll use this reply to you as an update to everybody as well. I just double checked the firing control group and everything seems to be fine. The hammer spring sent to me does seem to be awfully strong and I have another springs that I'll probably try tonight. I don't have a range trip scheduled anytime soon but I also think it can be better assessed with some live fire but that will take a little longer to happen.

Appreciate y'alls input!

 

[edzz]

Totally agree with @v0lcom13sn0w

Sounds like my first build that I experienced problems with, when discussing it with a buddy he asked if I was running it wet or dry. "Soaked" it down with CLP for break in and has behaved ever since. Now it runs lightly lubed as do my other AR's.

 

[Pepe-lepew]

There is something wrong if it drags going into battery when you hold the trigger back. The hammer should have no discernible change in pressure on the bolt when the trigger is pulled or not.

A new BCG with new gas rings will hang up when locking in if you ride the charging handle. You are not mistaking this for dragging?

AR's should not require break in. If parts are so rough they require break in to run reliably, those parts should be tossed and replaced with better parts.

 

[Deavis]

Take the upper off, flip it upside down and push the bolt into battery with your fingers.

Watch the interface with gas tube and key.

If the key is tight, staked and straight and its binding there the tube might be bent. Gentle bending if tube with a large flat head if its binding.

 

[PhillipeC]

There is something wrong if it drags going into battery when you hold the trigger back. The hammer should have no discernible change in pressure on the bolt when the trigger is pulled or not.

A new BCG with new gas rings will hang up when locking in if you ride the charging handle. You are not mistaking this for dragging?

AR's should not require break in. If parts are so rough they require break in to run reliably, those parts should be tossed and replaced with better parts.

Not riding the charging handle. Even when I charge and release it will drag for the first inch and then slam back into battery.

Take the upper off, flip it upside down and push the bolt into battery with your fingers.

Watch the interface with gas tube and key.

If the key is tight, staked and straight and its binding there the tube might be bent. Gentle bending if tube with a large flat head if its binding.

Upper saw thousands of rounds already. I just used it to test the lower. The lower is responsible for the drag, I'm not sure why.

 

[Unicykle]

I would guess there's either something out of spec with your trigger group, it's installed wrong or one of the trigger pin holes on the lower is out of Spec. Change the trigger group from a known working lower.

 

[PhillipeC]

Update for all that gave me their input and tried to help. Still didn't have any live fire but was playing with it last night and "fixed" the issue.
Just FYI this was a budget lower that I wanted to put together just for the sake of it. It is a PSA receiver and their cheapest parts kit. I swapped the hammer with other lowers to make sure the lower receiver itself was good to go and all was good there. The hammer caused the same issue on other lowers at the same time a different hammer didn't have the issue on the problematic build. I then narrowed it down to the hammer and after thorough inspection, the coating on it was a little thicker than usual and after sanding it a little bit and racking the bolt a few times it is as good as the other ones now. No dragging.

Thanks all!