98Z5V Posted May 18, 2015 Report Share Posted May 18, 2015 (edited) This is to assist with gas block alignment and spacing. How often have you worried whether your gas block is centered over the gas port in the barrel - is it off the shoulder? How much is it supposed to be off the shoulder? Did I get it right, or do I have to shoot it and find out, then take the damn thing apart again?... Don't worry about it, basically. For the most part, the port in the block is larger than the gas port in the barrel. Mostly. However, if you really want to check it all out, it's very, very simple to do, when you're using a set-screw type gas block. This info won't help for clamp-on blocks, but you can measure for that and confirm. That info comes later. Now, for the set-screw blocks... Here's the hardware for the example: Rainier Select 18" mid-gas .308 barrel, Geissele Super Gas Block. As you can see, the Rainier barrel is already dimpled, for use with a set-screw block. Not all barrels are dimpled, but that is an easy process to make happen. Next time I get a non-dimpled barrel, I'll go through it. Now, gas block manufacturers all do this same thing - on the set-screw blocks, they drill for the set screw locations, and the rearward set screw hole continues straight through, and becomes the gas port in the block. No kidding, check that out next time you get a new block. It's non-complicated machining. Here's a look THROUGH that rearward set screw hole, and you can see the gas port in the block: To exaggerate it, here's a punch, right down through: Easiest way to see how far you have to set that gas block off the shoulder, is to slide it on the barrel they way you'd install it - then flip the block 180 degrees. You'll turn the block upside down. You should be able to look THROUGH that rearward set screw hole, and center it on your gas port in the barrel. Center the block over the gas port in the barrel, and check the distance from the shoulder that it is right then. That's how far off the shoulder you'd need to mount it, to have everything centered up. Pretty simple process. ^^^ As you can see in that pic, the Geissele Super Gas Block will mount flush against the barrel shoulder on this Rainier barrel, and it will be centered. Here it is again, side view: Hope that helps somebody, somewhere, sometime. Have fun, check your $hit, build more rifles. <thumbsup> Edited May 18, 2015 by 98Z5V Quote Link to comment Share on other sites More sharing options...
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.