AR Forward assist

[printcraft]

Gerbil! I'm a Gerbil Trainer, you fool!


Fire/Medic, hence the username (though it is pretty subtle since most don't know what Irons are)

And now I'm having trouble getting the bolt to seat, so this, again, may well be moot. Sigh.

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[ol' poke]

And now I'm having trouble getting the bolt to seat, so this, again, may well be moot. Sigh.

Might need to look at a good cleaning and lube. Mine wouldn't even close the bolt, let alone rotate/seat. A good scrubbing and lube was the ticket!

Good shooting!

 

[IronsKeeper]

Might need to look at a good cleaning and lube. Mine wouldn't even close the bolt, let alone rotate/seat. A good scrubbing and lube was the ticket!

Good shooting!

Gonna try a nice thick lube tonight and hope that frees it up. Can't even take it apart currently. The BCG was lubed as it came from another build, but not this new upper. Lesson learned.

I'm determined make it function, but for those keeping score at home I'm sticking with known good guns for my roadtrip.

til I get function AND enough rounds on this pistol to actually trust it, range toy status remains.

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[IronsKeeper]

This problem did indeed "work itself out" with enough lubrication. Literally.

One way or the other, the gas tube/key is the problem. Probably tube since the BCG came from another build.

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[T-DOGG]

Ummm. It looks like you forgot to put a roll pin in that gas block to hold the gas tube in.

 

[churchmouse]

Ummm. It looks like you forgot to put a roll pin in that gas block to hold the gas tube in.

And the tube has rotated and is hitting the BCG.....probably.....

 

[d.kaufman]

Definitely have to say you forgot the gas tube roll pin. Seems like the forward assist is the least of your worries at the moment

 

[IronsKeeper]

Wow, y'all don't give a guy credit do ya?

Slamming the BCG home finally sheared the pin because the gas tube is oversized and would not fit inside the gas key.

That isn't my favorite kind of "break" in period, doncha know.

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[T-DOGG]

Wow, y'all don't give a guy credit do ya?

Slamming the BCG home finally sheared the pin because the gas tube is oversized and would not fit inside the gas key.

That isn't my favorite kind of "break" in period, doncha know.

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What is an oversized gas tube exactly?

 

[churchmouse]

Wow, y'all don't give a guy credit do ya?

Slamming the BCG home finally sheared the pin because the gas tube is oversized and would not fit inside the gas key.

That isn't my favorite kind of "break" in period, doncha know.

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In the multitude of AR's I have owned/assembled I have never seen this. Never heard of it. Not saying it is not possible but I guess I am asking how is this possible.....

And the tube has turned 90*s...

 

[d.kaufman]

Ive built quite a few in my time and have never heard of different diameter gas tubes. 223/566, 6.5 grendel, 308, 458 socom, etc all take the same diameter gas tube. The length is whats different. If it sheared the pin then the gas tube/block must not of been clocked correctly, allowing the bcg to keep slamming the tube, and finally shearing the pin. It had to take some force to shear the pin though.
I personally have never seen this happen.

 

[T-DOGG]

Ive built quite a few in my time and have never heard of different diameter gas tubes. 223/566, 6.5 grendel, 308, 458 socom, etc all take the same diameter gas tube. The length is whats different. If it sheared the pin then the gas tube/block must not of been clocked correctly, allowing the bcg to keep slamming the tube, and finally shearing the pin. It had to take some force to shear the pin though.
I personally have never seen this happen.

Exactly. A 300 blackout uses a standard AR-15 BCG and standard AR-15 gas tubes. The same BCG and gas tubes that a 5.56 gun would use.

OP, I'm really trying to help you here. Something is not right in your build. If the gas block and gas tube are aligned correctly, the gas tube should be able to wiggle a little bit where it goes into the upper receiver and the gas key on the BCG should allow the gas tube to slide in very easily. You shouldn't have to really force anything there. Yes a new BCG will have some resistance until the gas rings get broke in and seated.

 

[d.kaufman]

From the pic i almost have to believe maybe op used a midlength tube where a carbine length Should of been used? About an 1" difference in length between the 2 and that looks to be close to how far the tube in pic is shoved out the front of the block

Edit. Just remembered it was a pistol build. Maybe used a carbine length tube but needed pistol length gas tube

 

[T-DOGG]

From the pic i almost have to believe maybe op used a midlength tube where a carbine length Should of been used? About an 1" difference in length between the 2 and that looks to be close to how far the tube in pic is shoved out the front of the block

Or carbine length tube instead of a pistol length tube. A lot of 300 blackout barrels use pistol length gas and I'm guessing that's a 8.5" barrel.

 

[d.kaufman]

Or carbine length tube instead of a pistol length tube. A lot of 300 blackout barrels use pistol length gas and I'm guessing that's a 8.5" barrel.

Yeah. I edited my post. Forgot was a pistol build

 

[IronsKeeper]

I tried to place the gas tube into the gas key. It would not fit. This was after I had removed both from the pistol.

I forget what terminology I used, but I believe the gas tube is out of spec. I know all lengths and calibers are the same diameter (or should be).

Pistol gas tube, pistol gas barrel.

Here's some pictures. This is how it came out of the rail. The tube contour seems right, so it isn't upside down. The pin is sheared. The other piece fell out of the block.

There were some confusing shadows in my first picture, but- if I'm wrong I'll own it. If I misplaced the tube alignment, I'll own it. Or anything else.

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[Ruffnek]

Just remember man, it's a learning experience, happens to everyone at some point.

 

[sig1473]

Parts ain't parts.........

 

[Hop]

I'm going for a clocking issue as well. I do not trust those dimpled barrels to put the gas block on at a perfect 12:00. It leads to a gas tube entering the upper at an angle. The gas tube will hit the gas key, cause the bolt to drag & not fully seat, etc. A delta ring style AR barrel nut helps you see the problem. Most hand guards nowadays don't use those so it's harder to see that the tube is off axis.

 

[Double T]

where'd you get the gas tube? I'm thinking you got a carbine tube and not a pistol tube.