Gunsmithing Youngs bolt & carrier with Vltor upper

[Outlaw45]

I built an AR15 with the Youngs Mfg bolt and carrier in a Vltor upper. Shilen 20" barrel LaRue low profile gas block. Rifle length gas tube.

With one round in a magazine, it fires, ejects, but won't lock the bolt back. It either closes on a empty chamber or locks back on the front of the carrier.

I have noticed that when I slide the Youngs carrier back and forth in the Vltor upper with my fingers, it binds up toward the rear. Right where it would be when it locks back on the front of the carrier. Could one of these two parts be out of spec?

 

[exhogflyer]

Re: Youngs bolt & carrier with Vltor upper

That's classic short stroking, caused by weak gas impulse.Can you pull the bolt back with the charging handle? Does it release fine? If so look at the gas tube, gas block, make sure the gas block hole lines up with the barrel hole.
And make sure it's lubed like a virgin on prom nite...

 

[SpotcheckBilly]

Re: Youngs bolt & carrier with Vltor upper

Sounds like it's short-stroking. Your Youngs bolt carrier isn't one of those lightweight versions, is it?

 

[Outlaw45]

Re: Youngs bolt & carrier with Vltor upper

No, the Youngs I have is the 1/2 oz. heavier National Match version. When I cycle it manually it functions fine. It's only when firing rounds.

I do see a little powder burn marks on the gas tube where it comes out of the gas block. Maybe about 1/4" long. Gas is leaking there, but I wondered if that was normal. Maybe it's more than I thought. How would I stop it from doing that?

 

[serpnt]

Re: Youngs bolt & carrier with Vltor upper

The short stroke may bee too small a gas port on the bbl. The port size is relative to overall bbl length and whether rifle or carbine length gas tube. Any idea what size the port is???

 

[Grand]

Re: Youngs bolt & carrier with Vltor upper

Check the gas key fit with gas tube. Young recently had a recall because some of the keys had a tight fit. I sent two back myself.

 

[Hateca]

Re: Youngs bolt & carrier with Vltor upper

What stock are you running? What buffer spring and buffer tube are you running? If you have the wrong spring and or buffer tube this can cause the carrier group to stop short of its rearward movement.

If there is not a gap of approx. .25" from the bolt face to the rear of the bolt catch when the carrier group is held fully to the rear you have the wrong spring and or buffer tube in the weapon. If you have the wrong spring and or buffer tube the gap will almost be nothing and this will also cause you the issue you are having.

 

[Outlaw45]

Re: Youngs bolt & carrier with Vltor upper

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body">What stock are you running? What buffer spring and buffer tube are you running? If you have the wrong spring and or buffer tube this can cause the carrier group to stop short of its rearward movement.

If there is not a gap of approx. .25" from the bolt face to the rear of the bolt catch when the carrier group is held fully to the rear you have the wrong spring and or buffer tube in the weapon. If you have the wrong spring and or buffer tube the gap will almost be nothing and this will also cause you the issue you are having.
</div></div>
Magpul PRS stock and the buffer and spring I got from Brownells in their A2 stock completetion kit. Came with buffer, spring, and extention tube.

When I pull the charging handle all the way to the rear, <span style="font-weight: bold">there is </span>about a .25 inch of gap.

The barrel is Shilen's 20" drop in. I don't know the port size. I have a rifle length gas tube. It appears that everything is the right length. Wouldn't Shilen take care of drilling the right port size? If they drill the port out where only rifle length gas tubes can reach, I would assume they would make it the right size.

And as far as gas key fit goes, how do I check that? I took the bolt out of the carrier and slowly watched as I slid the carrier back and forth. It appears to be OK as far as I know. I'll call Young to see if I have a bad bolt and carrier.

 

[Outlaw45]

Re: Youngs bolt & carrier with Vltor upper

Just talked to Youngs Mfg. First off, great to talk, great customer service. I bought the carrier through Black Weapons Armory in Tuson. He said they don't know how to properly install the gas key and stake it. He told me to send it to him and he'd take care of it and refund my shipping. Wow!

He also said it's been a common problem with the Vltor uppers for being a tight fit with their carriers.