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Orava

Replaced barrel, BCG not cycling

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Hi,

 

A little about me. I was in the Army in the early '90s, so I know about shooting/maintaining the M16 well. I'm mechanically inclined and have worked a lot on cars but this is my first attempt at gunsmithing. This is also my first AR15.

 

Anyways, I replaced the barrel and bolt on my Bear Creek Arsenal 6.5 Grendel upper with a Ballistic Advantage barrel in .223 Wylde. The rifle fired fine but the bolt carrier group wouldn't move. The gas block came pre-installed but I had to remove it to get the barrel nut on. I noticed there was carbon around the gas block and someone watched me fire it and said you could see gas coming out of the block. I think the gas inlet on the block and the outlet on the barrel aren't lined up right but the weird part is that there is a hole on the bottom of the gas block and barrel and I put a roll pin through it. (It which it originally didn't have one.) Whatever reason, gas doesn't go from the barrel to the bolt carrier group and the bolt doesn't cycle when I fire it.

 

I'm willing to send it in to have it looked at. I bought it from Arm or Ally but I was wondering if Ballistic Advantage would be more helpful or if I should take it to someone locally.

 

I was using cheap Wolf ammo 62 grain because I was just breaking it in. I had to pull the charging handle back each time I fired but kept doing it figuring I'd sort out the gas issue later. I tried some Wolf 75 grain and it became really hard to pull the charging handle back. I stopped that after 4 tries and a lot of oil. I hope I didn't damage something.

 

I was going to remove the barrel and blow into the gas tube to see if it's blocked. If it is I'll wiggle it to see if I can get more air flow. I suppose I could attach a rubber tube with a zip tie to the gas tube so that I didn't have to remove the barrel.

 

Any thoughts?

 

Thanks

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Did you take the roll pin out of the gas block where it goes through gas tube?

 

The oin in the gas block is usually a taper pin not a roll pin. The taper forces the gas block down to a tight interface with the barrel. A roll pin may not do that. 

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There are two roll pins. One for the gas tube to the block and another under the barrel to align the block to the barrel.

 

I couldn't get the original roll pin for the gas tube to fit and used another one. That might explain my problem.

 

But the carbon is mostly coming out of where the gas block mounts to the barrel. Perhaps the tube I'm using isn't lined up rather than the block. Hadn't thought of that. Thanks.

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Possibly. You can use drill bits as pin gauges to determine if the gas block has a tapered hole or not. If one side is larger than the other then you have a tapered pin. If both sides are the same size I would contact the manufacturer and ask if it is supposed to be tapered as they drill them straight and then taper drill them so they may have missed that part. 

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Interesting. Thanks for helping me out. Is there a standard size for the gas block to gas tube?

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8 hours ago, Orava said:

Interesting. Thanks for helping me out. Is there a standard size for the gas block to gas tube?

5/64 X 0.3125 (5/16) is the norm.

 

I take it the gas block is pinned only for alignment. Does it also have set screws?

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Gas block and barrel are not aligned sounds like. Hopefully they drilled the barrel correctly. Because if they didn't, you're gonna have to use a set screw block.

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Welcome to the board !

 

I have no doubt the brain trust here will get you back in business ASAP. 

 

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3 hours ago, bamashooter said:

5/64 X 0.3125 (5/16) is the norm.

 

I take it the gas block is pinned only for alignment. Does it also have set screws?

It does have set screws. I'm thinking more and more that the problem is the gas block and the gas tube. I'm going to see if I can blow air through it.

 

Thanks for the replies, everyone. Much appreciated. It's been fun to mess with this and ARs are fun to shoot.

 

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PS, why would the bolt be stuck after shooting that steel-cased Wolf 75 grain ammo? It moves back and forth just fine when I dry test it and the 62 grain didn't seem to bother it.

Edited by Orava
more detail

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Well, the gas tube is completely blocked somewhere, so there's not much of a mystery now.

 

I just learned the hard way to check the gas tube before taking a new build to the range.

 

I feel a little foolish, but, you don't know what you don't know and this was my first attempt.

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3 hours ago, Orava said:

I feel a little foolish, but, you don't know what you don't know and this was my first attempt.

Screw that shat. You'll be fine. When I check for flow, after I draw lines, etc to ensure a perfectly straight line from GB to bcg, I do the following:

Install gb and get its gas port aligned with the barrel gas port somewhat. This is simple due to the GB port being much larger than the barrel port (normally). Snug the gb enough where you can still move it to and fro.

With the bcg removed and the tube exposed in the upper,

I totally block any air flow in the barrel by plugging the barrel extension with whatever's handy. Plug it well (perfectly).

I then blow through the muzzle with a finger plugging the open end of the tube within the upper.

I will then "slide" the gb ever so slightly to and fro to detect maximum flow.

Satisfied with flow and alignment, I cinch it down.

 

Holler back regardless.

Edited by bamashooter

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I had an adjustable block that had the port drilled forward of the proper place. IT did not run any gas at all. It would have been perfect for a fake single shot as the port is blocked completely. They drilled it through the FRONT screw not the back.  I still have it in case I decide to build a dedicated straight pull sometime.

 

Greg

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Got off work early so I decided to take it out to the range and it shot great and even cycled those rounds that were getting stuck with ease.

 

Thanks everyone.

 

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