Hello all; hope all is well. Can someone please enlighten me? I want to buy an adjustable, rifle length gas block and tube system for my 18 inch barrel dpms .308 win. What is the gas block journal, and is it the same for an AR 15? Thank you.
I believe you are asking about barrel diameter? You need to match the gas block to the size(profile) barrel you have. There are quite a few different sizes and some of the common ones I see often are .750 and .625. If you don't know you can simply measure your barrel where the gas block sits(with it removed) with a set of calipers. Also depending on how your gun is set up you will need to know the outside dimensions of the gas block too. If it's exposed it's not a big deal but if it's under the handguard you will need to know to make sure it will fit. There are also different gas port sizes. I could be wrong on this but i think they are different for different size gas blocks and I'm pretty sure they should all come they way they are supposed to unless you're doing some sort of custom system. I have always just made sure i had the right barrel size and outside diameter to fit under my hand guard and never had any issues with port sizes.