Gas Block Installation

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I'm in the process of aquiring parts for my first AR build and have a question WRT to the gas block and barrel. I'm looking at a low profile YHM with set screws and one with pinch screws. Any preference here? Also, is having the barrel dimpled absolutely necessary for the installation of the set crew variety? Any chance my barrel may come pre-dimpled? I have a 14.5" Green Mountain on order from the GB if that matters.
 
What are you going to use for a forend? Some of the smaller diameter ones (a MI gen 2 SS for example) will not fit over a pinch block style gas block, You need the set screw type.
 
Pinch screws, assuming the handguard accommodates.

The only advantage to the tapered pin style is that both set and pinch screws can loosen under sustained full auto fire. Tapered pin installs in non-factory environments are generally not practical since the holes in the gas block, and the tangential holes in the barrel, are drilled in a single operation.
 
The only Green Mountain barrel I've worked with had the dimples for the gas block set screws. Really helped to make sure the alignment was correct. Use some blue LockTite on the set screw threads and you shouldn't have any issue (in semi-auto fire).

I would advise a test fit on the barrel, with the gas block, to see how tight it's going to be. You might want to take some wet/dry sandpaper to the inside of the gas block (to open it up a few thousandths). The one GM barrel (with an ICE Arms stamp on it [rolleyes]) was a REALLY tight fit to the gas block. It was a YHM gas block too.
 
I've used both. I prefer the pinch screws just because its easier. Never had it come loose as long as you use some loctite. I know a lot of people feel the set screws are more secure. The only time I used set screws was on a barrel that had the dimple, so that made it easy. It was a Wilson barrel, so not sure about GM. If you've got a decent drill press you could mark and add a dimple where you needed it pretty easily for added comfort.

I actually like to use the two-piece YHM gas blocks when I can fit them under the handguard. Easy to take off if you ever need to, without removing the muzzle break (benefit if you live in MA and weld it on).
 
What are you going to use for a forend? Some of the smaller diameter ones (a MI gen 2 SS for example) will not fit over a pinch block style gas block, You need the set screw type.


Thanks for the replies.

Not sure if anyone has any familiarity with with this unit, butI am going to be using UTG PRO Rifle Length 13" Super Slim Free Float Handguard.

http://www.leapers.com/prod_detail....el_15&level2=Handguard&itemno=MTU006SS&status=

Sounds like I should wait til I have the barrel in hand before I purchase a gas block to see if it's dimpled. I was hoping to grab all the parts beforehand so I could start assembly as soon as the barrel arrived
 
Thanks for the replies.

Not sure if anyone has any familiarity with with this unit, butI am going to be using UTG PRO Rifle Length 13" Super Slim Free Float Handguard.

http://www.leapers.com/prod_detail....el_15&level2=Handguard&itemno=MTU006SS&status=

Sounds like I should wait til I have the barrel in hand before I purchase a gas block to see if it's dimpled. I was hoping to grab all the parts beforehand so I could start assembly as soon as the barrel arrived

I'd contact Green Mountain to find out if the barrel you ordered is dimpled or not. Instead of just waiting for it to arrive (unless you'll have it tomorrow).

That looks like a nice handguard. A regular low profile gas block should work without issue (as they claim). Even if you get the gas block ahead of time, chances are you could either sell it for what you paid (as long as you don't bugger it up or mount it) or keep it for a future build. It also looks similar to the MI handguard I'm looking at. The mount system of the two differ, but they otherwise look pretty much the same. There's rumor of a group buy coming up for the MI handguards. So, if you've not already bought the UTG model, you might want to wait a little.
 
Tapered pin installs in non-factory environments are generally not practical since the holes in the gas block, and the tangential holes in the barrel, are drilled in a single operation.

I've done taper pins in my basement. It was actually a lot easier than I thought it would be. Drill press, bit (#31 I think but I could be wrong,) and a 0/2 reamer and handle. Probably took me 30 minutes and that was going slow.
 
Just got my GM barrel, dimpled for set screws. I am using a YHM low-pro block. With a little oil, block slid on with very minor interference. Hint, make sure the set screws in the block are backed all the way out, should have no problem [grin]
 
Just got my GM barrel, dimpled for set screws. I am using a YHM low-pro block. With a little oil, block slid on with very minor interference. Hint, make sure the set screws in the block are backed all the way out, should have no problem [grin]

What barrel do you have? I contacted customer service about my 5.56 14.5" carbine I have on order and they stated it does NOT come dimpled.
 
I have a YHM brake I'm using for my build. According to the YHM website, they will install the brake for free. Has anyone used or familiar with the quality of this service they provide?

Also, if I were to go this route, what would be the minimal amount of assembly that I could perform before doing so in an effort to minimize shipping costs? I assume the barrel nut for my free float would need to be slid over the barrel and the gas block(and gas tube?) installed prior to them pinning and welding? Or should I just assemble the entire upper receiver and then ship? Obviously, I'm floundering here in my newbness, any guidance would be much appreciated.
 
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I'm not sure about what YHM does for installing a brake. Do they mean they will weld it in place for you and everything? Or just thread it on and straighten it? If they'll weld it, that might be worth it, but if its just to thread it on, I'd save yourself the shipping cost and do that yourself.

If you do want to ship it, you would probably need to put on the barrel nut and gas block at the very least. Check and see, maybe you will be lucky and the barrel nut will fit over the break. I've used some breaks that were small enough diameter that the nut could clear it.

I would then make sure that your free float tube will fit over the muzzle break, otherwise you better thread that on too before the break is installed. Oh, and you would need to have the gas tube installed before that too.

If your free float tube fits over the break, I would probably wait to do the gas tube, so it doesn't get damaged. You can lightly install the gas block without loctite. Then when you get it back from YHM, loosen it up, push it down the barrel a few inches, and then install the gas tube into it and reposition the gas block to permanently install it in place. Then put on your FF tube over everything and you'll be good to go.

Not to be overly cautious, but you may want to rethink all this. If I were you, I would take your barrel, mount it to your upper receiver and torque it down. Install the gas tube and block. Then go to the range and test fire the gun for proper operation. You can test fire without the FF tube, and without the muzzle break. This way, if there is anything wrong with any of the parts, you can diagnose and fix it before its too late. Once the muzzle break is welded on, it is going to be very difficult.

I realize that this all seems incredibly unlikely, but I've had two builds (built with quality parts) that I had to take apart and replace faulty components. One was a bad gas tube and the other was an undersized gas port in the barrel. If the muzzle break was already welded, it could've been a nightmare.

One thing...IANAL but note that you are breaking some laws when you go to the range to test fire it without the muzzle break welded on. So just keep that in mind and act accordingly.
 
I'm not sure about what YHM does for installing a brake. Do they mean they will weld it in place for you and everything? Or just thread it on and straighten it? If they'll weld it, that might be worth it, but if its just to thread it on, I'd save yourself the shipping cost and do that yourself.

If you do want to ship it, you would probably need to put on the barrel nut and gas block at the very least. Check and see, maybe you will be lucky and the barrel nut will fit over the break. I've used some breaks that were small enough diameter that the nut could clear it.

I would then make sure that your free float tube will fit over the muzzle break, otherwise you better thread that on too before the break is installed. Oh, and you would need to have the gas tube installed before that too.

If your free float tube fits over the break, I would probably wait to do the gas tube, so it doesn't get damaged. You can lightly install the gas block without loctite. Then when you get it back from YHM, loosen it up, push it down the barrel a few inches, and then install the gas tube into it and reposition the gas block to permanently install it in place. Then put on your FF tube over everything and you'll be good to go.

Not to be overly cautious, but you may want to rethink all this. If I were you, I would take your barrel, mount it to your upper receiver and torque it down. Install the gas tube and block. Then go to the range and test fire the gun for proper operation. You can test fire without the FF tube, and without the muzzle break. This way, if there is anything wrong with any of the parts, you can diagnose and fix it before its too late. Once the muzzle break is welded on, it is going to be very difficult.

I realize that this all seems incredibly unlikely, but I've had two builds (built with quality parts) that I had to take apart and replace faulty components. One was a bad gas tube and the other was an undersized gas port in the barrel. If the muzzle break was already welded, it could've been a nightmare.

One thing...IANAL but note that you are breaking some laws when you go to the range to test fire it without the muzzle break welded on. So just keep that in mind and act accordingly.

LOL. You got it correct right out of the gate, after that, not so much.
 
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