ar15 won't cycle.

4

4seasons69

New member
Okay so I took my freshly built by me ar to the range today. It shoots but won't cycle. So I have take the upper apart. It seems like everything in the gas system is aligned correctly.

With the hand guard end cap in the hand guard the last 1/2 of sliding the gas block and tube in gets a little tight. Not sure if this could be the cause.

My next idea is that possibly the gas port in the barrel is not large enough and not letting enough gas through.

Now here is what I think it is. When you cycle the bolt carrier there are a couple tight/sticking points. It take a little force to in tall it in the upper receiver. Not a ton but it doesn't seem right to me.

I'm assuming the bolt carrier should be able to slide smoothly and easily through the upper? Should I take some emery cloth or fine grit sand paper and try and polish off those sticking points?

Any thoughts, ideas,or opinions are appreciated.
 
How is it failing to cycle? Failing to open at all? Partially cycling? Failing to feed, extract? What is happening?

Does it cycle normally when actuated with the charging handle?

Are you sure that the gas port in the barrel is properly aligned with the port on the block? Is the gas tube port properly aligned with the block port? Does the gas tube fit properly into the gas key in the action?

Do you have an adjustable gas block, and if so, is it closed?
 
Originally Posted By: VarminterrorHow is it failing to cycle? Failing to open at all? Partially cycling? Failing to feed, extract? What is happening?

Does it cycle normally when actuated with the charging handle?

Are you sure that the gas port in the barrel is properly aligned with the port on the block? Is the gas tube port properly aligned with the block port? Does the gas tube fit properly into the gas key in the action?


Do you have an adjustable gas block, and if so, is it closed?


The bolt carrier will open partially. Where it stops is one of the tight spots. To me it seems like it is either A. Not getting enough gas or B. The bolt carrier fits to tight.

For the most part it would cycle manually with the charging handle. I would say %30 of the rounds shot I had to use the forward assist to fully close the bolt.

the gas tube and gas block alignment look good to me. I can blow through the tube easy with no resistance. The roll pin in the gas tube was a tight fit. So it would require a new gas tube if that's the problem.

Based on the marks on the barrel it looks like the gas port in the barrel was close to the edge of the port in the gas block. It could be off a tiny bit that I can't really see.

The gas tube and gas key slide together in the action nicely. No signs of them contacting each other.

it is not an adjustable gas block.
 
Yip more details to determine how bad the problem is. Will it extract partially but not eject? Eject but not pick up the next round or lock back? No bolt movement at all?

The bcg dragging issue could be it dragging on the hammer. I use RRA 2 stage triggers and I've had a couple where the tolerances with certain uppers paired with certain lowers caused the bcg to drag hard on the hammer. A quick check is to pull the hammer and see if it cycles much easier.

May not be your issue but it is one not too many have experienced or would think of till it happened to them.
 
Yes. If i try and install it without the charging handle it will actually get stuck. The charging handle guides it enough that it doesn't completely get stuck
 
The bolt should slide easily. Is it the carrier binding or the bolt lugs binding. When you say wont cycle do you mean it isnt ejecting the spent case or short stroking?
 
Last edited:
Very surprising that it's binding so badly that it stops upon firing, but you're able to actuate it by hand. My gut reaction would be that if it's binding so much that a healthy DI gas punch is failing to overcome it, then you should never have fired it, as you've have felt substantial resistance to cycling by hand. You said you built this thing, you shouldn't have just now gotten surprised that it's binding, and you shouldn't have fired it after feeling that bind.
 
Originally Posted By: SteveB22250Did you maybe tweak the upper while you tightened the barrel to spec???

Anything is possible. I used an upper vice block and followed yhm's instructions on free float tube installation
 
Originally Posted By: Widow maker 223The bolt should slide easily. Is it the carrier binding or the bolt lugs binding. When you say wont cycle do you mean it isnt ejecting the spent case or short stroking?

When you fire it the bcg only moves back about a quarter inch. And it wouldn't always completely seat the round in the chamber. I would have to use the forward assist
 
Originally Posted By: VarminterrorVery surprising that it's binding so badly that it stops upon firing, but you're able to actuate it by hand. My gut reaction would be that if it's binding so much that a healthy DI gas punch is failing to overcome it, then you should never have fired it, as you've have felt substantial resistance to cycling by hand. You said you built this thing, you shouldn't have just now gotten surprised that it's binding, and you shouldn't have fired it after feeling that bind.

Cycling the rifle manually without ammo it cycled and felt fine. The bolt would always close completely and felt okay that's why I brought it to the range. I don't have any .223 snap caps and wasn't going to try cycling live ammo through it in my apartment.
 
Originally Posted By: 204 ARSo cycling it without ammo it seems fine still?

Here's where I'm at now. Spent most of the day at my buddies messing with it. I think having the hand guard end cap in was causing the gas tube to be misaligned. We were very careful about installing the gas block and gas tube making sure they were properly aligned. We took the rifle in his back yard (which is wooded) and manually ran some ammo through it. It feels much smoother with and without ammo in it now. The only time it won't completely feed a round sometimes is the first round with a full magazine.

There is also what looks to be over spray from the camo coating on it in the inside of the reciever. I'm going to try and polish some of that out and see how it feels.
 
Also I did have the rifle in to a local shop that specializes in ar's yesterday to have the head space checked and they didn't bring up any issues with the way the bcg slid in and out of the reciever
 
Back
Top