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Posted: 4/10/2007 9:17:31 PM EDT
| I need to install a micor gas block on one of my rifles. I have heard the only proper way to do this is to pin it. What exactly is pinning it? Almost all of the micro gas blocks I have seen mention set screws...not pins. What if the set screw/pin holes dont line up with the notches in the barrel? |
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More then likely the screws won't line up with either one or both slots. Pinning it means drilling a hole and using either a straight to taper pin like standard A2 front sights/block assembly that was removed from the barrel. Usually (actually all I have seen) the set screw blocks have the rear hole right below the gas hole in the barrel. Is there a slot under the barrel? Which block are you planning on using. The smaller ones like Vltor and CMMG's may not cover the front slot at all depending on how far forward it was drilled. The LaRue and some of the others are extended to cover up the problems encountered with using a barrel that had a standard sight installed. Gas blocks don't come drilled for pins because there is almost no chance their holes would line up with the factory holes because thery are different on every barrel. If you dimple the bottom of the barrel correctly in the rear hole and loctite the screw there is no chance it will move. You might have room to dimple both holes or the front might fall into the forward pin slot. Set screw blocks can be pinned but most people will have to send it out unless they have access to machine shop equipment or machinist/gunsmith buddy to do it. |
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You should have at least a dimple on the rear most set screw. If there is room have the front done also if the block you choose has two screws. Pinning is just added insurance but if the screws are set into dimples correctly the bloc k will not move. With just the small gas block you don't have the leverage of a full A2 sight tower attached to the block to move it. |
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I am just a little concerned because I had my armorer put a micro gas block on another rifle of mine and the holes didn't line up so he just locktited it. 800 rounds later and I had a VERY poor single shot rifle. He drilled small holes in it and reinstalled it and so far no problems. It's just on my new rifle I don't want to take any chances. What do you mean the small gas block doesn't have the leverage...is this a good or bad thing? |
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Just using the set screws with out dimpling the barrel will cause the block to move because the screws can't bite in the barrel very well. The dimples will allow the screws to set into the hole and as long as the screws don't come loose (red loctite on the screws) the block will stay in position. I spot my barrels with set screws .030 to .050 deep with an endmill so it isn't going anywhere. The levarage I refer to is the sight tower on the standard sight sticks up and can bang on or snag things. Since it is 2 inches tall (just a guess since I don't have one here at work) it would be easier to move it out of alignment if it were set screwed in place. You can even stake over the set screws if you like to make sure they won't come out but that is over kill and makes it a pain in the butt should you want to take the block off for any reason. |
If you ever use a piton set up the pin is required to prevent the screw from deforming and cusing the gas block to shift. You can see how my gas block is pinned in this pic at the bottom of the block with a single pin. It does not have any screws installed in the threaded holes because they are not needed. Set screws can come loose from vibration (Ihad this happen) unless red loktited and then they are pretty close to impossible to remove.
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