I was having a conversation with a gunsmith I know and got on the topic of gas blocks. On builds I do for others and some of my own I use set screw gas blocks but for my serious use rifles they are all pinned. I do not have the equipment to pin myself so I either buy a barrel that has one already pinned or send it out for that. He brought up an idea I haven't really heard about and that was staking the the set screws. After you secure the set screws (adding a dimple in barrel if you see fit) add a thread locker and stake the screw. He said if you buy quality gas blocks made from similar steal as the barrel that they won't budge or back out. After thinking it over I think he may be right on this. If you buy steal gas blocks that will expand at the same rate as the barrel as it heats up the screws have less of a chance of moving on you as opposed to using aluminum blocks that will expand faster than steal. Now if you stake the screw there is no possible way for the screw to back out, therefore, not coming loose. The only way, I THINK, the gas block would come loose is if the nubs of the screw eventually wore down, which i think is rather unlikely because there is no movement or rubbing taking place. Add the fact that most are under rails, I really don't think they are going anywhere even under sustained fire.

Have you, or anyone else here, ever had properly torqued and loctited screws back out to begin with?

I was doing some reading on this the other day, and I noticed some guys saying they tighten the screws down with some blue loctite, then they tighten the screws down a bit more when they are shooting and the barrel has heated up.  They were on other sites, so I couldn't point out to them that all they are doing when the do that is breaking the "lock" that the loctite is providing once it has cured.

And people wonder why their gas blocks come loose.

I haven't personally. I have always used pinned blocks during courses but I am going try a pinned with the method I described next time to see what happens.

I agree that all those people did was break the loctite once they decided to tighten the screws a little more once it was set. I always loctite mine and torque down as hard as I can by hand without stripping the screw or breaking the allen wrench and none have moved. I have run them under some decent sustained fire but nothing compared to what I have done to others. I think if you stake the screws it is, for sure, not moving on ya.

You might want to invest in some torque wrenches.  Those screws are rated at something like 68 inch pounds max, so you should only be torquing them to something like 50 inch pounds at most.

I am still curious to see how many people have actually ever installed them properly and had them come loose.  I am not 100% sure.  But I do not think that a gas block is made from the same softer steel, as other components which are routinely staked, which would lend itself to staking, and without actually creating a stress point which would have a higher propensity to crack.  This might be why you don't see it done.

Another ARFCOMer described using two screws in a single-screw gas block.

He loctited the first one in, and then put the second screw in over the first one.

I've had my low profile gas blocks pinned, but that's just me.

I just dimple the barrel for the setscrews on the low pro gas blocks.. then use red loctite.. no issues.

I've had them come loose.

The heat generated by firing makes loctite unreliable. (How do you remove a screw with loctite? - heat, right?)

The staking is a good idea and has been discussed here before. The torque stress is still on the screw, so it does not take much to simply provide a little resistance on the screw to keep it from backing out.

That being said, having had them come loose (not staked), and having recently did my own chop job on a pinned FSB, I'll take the chop job every time.

It isn't just heat.  It is a certain amount of heat.  And the heat alone is not what makes the loctite give.  It is the heat, which has softened the loctite, provided it has hit the proper temperature point, and the act of turning the screws or bolts, overcoming the torque.

Leads me yo another question. I have carbine length bcm barrel on one of my builds and am wanting to put a midlength rail on. The front sight is pinned so I was contemplating taking a dremel to it. Is there any problems with weakening the metal or causing possible stress points by cutting one down.

In my opinion staking the screw on set screw type would be extremely effective because it prevents the screw from moving even if the thread locker melts away.

There is not an aluminum gas block made that belongs on a AR-15.


High pressure, extremely hot gasses forced through a small orifice tends to cut through aluminum like a gopher in soft dirt.





ETA: Steel not steal (unless you steal a steel gas block)

yeah about that.......Work habit. The word "steal" comes up a lot and I type it a lot. Force of habit hahaha

Who advertises/sells steel versus aluminum gas blocks?

If that is true, why has every after market gas block I could find in the past few minutes been made of aluminum?

It seems to me that aluminum works just fine for the application.

A lot of people sell aluminum gas blocks. Here is one example and there are countless others...

http://www.brownells.com/.aspx/pid=40265/Product/AR-15-M16-GAS-BLOCKS

That is what I am saying.  If they were not suitable for the application, why do they dominate the market?

Not sure. I know people that use them. I prefer steel ones, personally.


For people who cut there front sight base down to use under rail. Are you cold bluing them after taking a dremel to them to keep them from rusting???? Something needs to be done to keep them from rusting up especially if it is a duty rifle.

The FSB does not get that hot during the cutting. I cut a little, check the line, let it cool some, and cut some more. I had a can of computer air that I could flip upside down and use to cool it off faster if I thought it necessary, but it's not really a hardened, hi strength hi stress part.  I believe it gets much hotter during firing.

On a side note, I don't think you'll be happy with only a midlength on a carbine gas system. The end of the handguard would basically come to where the front end of the (now cut off) gas block would be. I'd go at least 11". I have 3 13" rails on my 16" guns and think they're great.

Well I have all the stuff here available to me now. I may change out the rail at later date. But I have a couple midlengths I like already