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Sticky AR15 bolt

7.6K views 24 replies 10 participants last post by  Nards91  
#1 ·
I just finished my first ar15 build. When I pull back the charging handle and let it go, the bolt doesn't always go all the way forward and it will be a pain in the butt to use the forward assist to push it forward.
I bought a complete PSA upper, minus bcg and charging handle. Bought those separately from psa.
I haven't shot it yet. Is it just a break in thing or should I have a gunsmith check it out to make sure it's all good?
 
#5 ·
I built one that took a bit of cycling to 'break in'.

Go shooting it a few times. You will probably be fine.
STOP!!
Before you go and shoot it......
I had a similar problem and I couldn't figure it out. After watching a few YouTube videos on proper lubrication of an AR, I learned that the BCG has 2 small holes in it (seen through the ejection port)
Image

Put a drop of gun oil in each hole and work the bolt in and out of the carrier.
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The "O" rings on the bolt are not sliding freely and they are causing the bolt to not function properly.
After you do this, work the BCG by actuating the charging handle a few times to work the oil into the rings.
Once it works in, it should seat properly and you can safely shoot.
Enjoy the new toy and shoot true! :D
 
#9 ·
#15 ·
Wondering that since this is a new build, maybe the gas tube isn't seating all the way into the key...? Just a thought
it's a possibility....is the Key staked?
 
#16 ·
Glockinator19 said:
Did you get it figured out Nards?
I followed the advice of RRoss. It isn't sticking too bad anymore. When the bolt doesn't fully seat in the chamber, the forward assist is much easier to use to push it forward. Still not as smooth as my wife's stag model 3, but getting there. I'll keep cycling it and if it doesn't smooth out soon, I'll get it looked at.
 
#17 ·
I followed the advice of RRoss. It isn't sticking too bad anymore. When the bolt doesn't fully seat in the chamber, the forward assist is much easier to use to push it forward. Still not as smooth as my wife's stag model 3, but getting there. I'll keep cycling it and if it doesn't smooth out soon, I'll get it looked at.
Glad to hear it helped. Did you grease the other contact points of the carrier that make contact with the upper?
 
#19 ·
#20 ·
RRoss said:
STOP!!
Put a drop of gun oil in each hole and work the bolt in and out of the carrier.

The "O" rings on the bolt are not sliding freely and they are causing the bolt to not function properly.
After you do this, work the BCG by actuating the charging handle a few times to work the oil into the rings.
Once it works in, it should seat properly and you can safely shoot.
Enjoy the new toy and shoot true! :D
As an old Infantryman well versed in all things M16, I can say you are probably correct in your diagnostics. Well done!

The bolt/bcg interface is easily overlooked. Also, make sure the thin gaps on the O-rings are well offset and not in line or nearly so.
 
#22 ·
I always make sure to keep the 3 rings with the gaps spaced out like a triangle, where they are evenly spaced. Don't keep them lined up
...an equilateral triangle or isosceles triangle?
 
#23 ·
....sorry couldn't resist