Cycling Issue

**a376z** · 11-30-19, 07:41

Hello
I had dropped off all the parts for a AR build with a local 'smith in August. Most of his reviews were positive but I'm thinking I might have given him something that's not in his expertise. After several attempts to get some info out of him this is what I got ......

"I thought the gas tube was too long so I ordered a new one. That is not the case.
The gas block has been fitted to the shoulder of the barrel, at its correct point. When the bolt is dropped down, it will not seat fully into battery, making me think there is something to do with the gas tube/bolt. When the bolt does seat completely into battery, it forces the gas tube ever so slightly forward that it turns the rifle into a single shot. Now, I am trying to figure out what the actual issue is. Is it the gas key, gas tube, or bolt itself. "

The barrel did not come with a gas port. Could he have drilled the port too small?

Any suggestions much appreciated.

**dmd08** · 11-30-19, 10:07

My guess is the gas block is not supposed to be on the barrel shoulder. If that's the case it could push your gas tube into the receiver too far and he may have drilled your gas port in the wrong spot.

ETA: What barrel and gas block are you using?

**a376z** · 11-30-19, 10:24

Originally Posted by dmd08

My guess is the gas block is not supposed to be on the barrel shoulder. If that's the case it could push your gas tube into the receiver too far and he may have drilled your gas port in the wrong spot.

ETA: What barrel and gas block are you using?

The barrel is a 16" 6.8 SPC:

https://columbiariverarms.com/produc...-configurable/

The gas block is:

https://www.brownells.com/rifle-part...prod80559.aspx

Before I gave him all the parts I dry fit it all together and it the only issue I saw was that the gas tube was too long based on the tick mark on the side of the receiver. I marked it and showed it to him when I dropped it all off.

**dmd08** · 11-30-19, 12:05

That gas block is kind of unique for a regular AR build and I don't know anything about it. I don't know what to tell you. Are you sure it's compatible with what you're trying to build?

**Clint** · 11-30-19, 12:10

Link doesn't work.

Is that a 308 barrel?

The gas tube is for the Colt LE901, which is likely a little different that standard mid length.

**a376z** · 11-30-19, 12:32

Originally Posted by Clint

Link doesn't work.

Is that a 308 barrel?

The gas tube is for the Colt LE901, which is likely a little different that standard mid length.

It's a 6.8 barrel

Try this

https://columbiariverarms.com/produc...-configurable/

**a376z** · 11-30-19, 12:47

As far as I know the only unique thing about it is the sight is mated to it. Other than that it's just a GB. It's the same FSB on the Colt 901's and 6940's.

The only thing I can think of causing issues would be the inside diameter of the gas tube but I don't think they are different, are they? The proper gassing is dependent on tube length and port size, no?