First AR Upper Build - gas block question

View · by **northernbird** on Mon May 06, 2013 8:31 pm

So I've assembled several lowers, but this is my first shot at assembling an upper. I've got a 20" wilson combat SS Bull Barrel, .936 at the rifle length gas port, with no indents under the barrel. I've got a couple questions here.. Do I need to go with a clamp on style gas block, or would the set screws on a normal low profile gas block hold it correctly?

This is going to be a bench/bipod gun with optics only.. not planning on iron sights. Theres not quite the huge number of options when looking at a .936 gas block, but theres still alot of them.. other than the adjustable ones, is there really any difference in these things? The pickings are pretty slim right now for folks having anything in stock so I'm wanting to know if theres a good reason to hold out for a 'big name' gas block or if they are all more or less the same.

Thanks.

View · by **Erik_Pakieser** on Mon May 06, 2013 8:45 pm

Pin-on > Clamp-on > Set Screws

At least, that's been my experience.

View · by **AR-15collector** on Mon May 06, 2013 8:51 pm

+1 with Erik. No matter how tight you screw a set screw, it could still come loose.

View · by **northernbird** on Mon May 06, 2013 9:52 pm

Thanks guys.

View · by **Dave** on Mon May 06, 2013 10:10 pm

They all can be fitted to run reliably, but Erik's post is generally right.

In non-adjustable blocks, there is no performance difference, assuming all are manufactured correctly (location & diameter of gas port, fit of gas tube & roll pin and indexing of each, and fit to barrel). Even a sloppily made one will probably work fine though.

View · by **JFettig** on Mon May 06, 2013 11:23 pm

I always install the gas block, lightly tighten the screws to make a whitness mark, then dimple the barrel and install

View · by **Hmac** on Tue May 07, 2013 5:36 am

Set screw blocks aren't bad if the barrel is dimpled for them, and if you're going to have the barrel dimpled, you might as well go all the way and have it pinned. But I agree that getting a clamp-on gas block is a reasonable second-best choice. Bear in mind when selecting the grade of threadlocker that that gas block gets pretty hot and typical blue loctite won't necessarily hold at those temps.

View · by **UnaStamus** on Mon May 20, 2013 9:38 pm

Set screws will hold for a long time, but you have to use the right threadlocker to hold them in place. BCM uses a super high temp green Loctite that cannot come off under normal service load. They have to use a blow torch for several minutes to release their gas blocks. This is an option, but you need the barrel dimples to accommodate the set screws.

There are jigs you can buy that will allow you to either dimple or tap your barrel using either a drill press or a regular hand drill.

View · by **northernbird** on Mon May 20, 2013 10:50 pm

Thanks for the response. I found a low pro Yankee Hill Machine clamp on gas block that works great. I actually got the 15" MI hand guard today and just finished assembling the upper about 30 minutes ago. Things went well and I cant wait to head out with my dad and shoot it. Feels pretty dang good to do a complete build.. just need to find some more $$ to do it all over again.