Ar-15 gas block dimples

Gas blocks and barrel dimples. This seems to be the new way to install gas blocks. Companies like SOLGW, and BCM to name a few are doing this.


(Do not do this. It is for entertainment purposes only)

Every time I buy a new rifle I remove everything and re-check all the screws and headspace of the firearm. Today this is what I found!

That’s right no dimples for the gas block fasteners.

Remove your gas block and make all required measurements first.

Set up your DRO or get out a piece of paper and start recording measurements from your center finder in your chuck.

I use a Starrett center finder. Find forget to subtract the diameter of the tip of the center finder in your equation.
Set up the barrel in the vice with v-blocks.

Use a center / starter drill for this. They don’t bend like conventional drill bits do.

Use a little cutting oil and always set your depth stop on your machine.

Drill and move the table to the second position and drill again.

Don’t go to deep. Just enough to give the fasteners a nice dimple to center into and rest.

Now degrease and heat the barrel with a heat gun.
Grab a q-tip and some cold bluing. Do this 2-3 times. Wash with water and re heat or use air to dry the newly blued area.

Now heat the area once more and apply a quality oil.

Apply high strength thread locker on your fasteners.

Now torque the fasteners to the appropriate specifications.

Remember be safe and have fun!


Very good information to have.


Thank you Dan. Truth be told I was going to drill and pin this one. But given that a lot of respectable companies are doing it this way I tried it too.


I guess I never really gave it much thought. Never had one move on me. But with my gunsmith classes now going, I should pay attention to this kind of thing.


Good stuff, switchpod :+1:


Whats funny is 10 years ago a lot people wrote BCM off for not using pinned gas blocks. Now a lot of companies do not pin them.


This is true but if someone wants a truly “bombproof” installation that will take a real beating then pinning is still the way to go. Most shooters will never really run their AR hard enough to need a pinned gas block but for those who train hard and regularly then it is still the way to go.


True, no argument there. I will say that I would still like to see pins on all gas blocks.
The only defense dimples have is that there is no bayonet lug on the gas blocks, and now days the hand guard comes over the entire gas block shielding it.

As I stated above I almost went the pin route.


Makes sense, same reason I dont run adjustable gas blocks. I dont mind it either way though. My Colt is pinned.


My colts pinned gas block is very sleek, it looks like they shaved down a FSB to fit under a rail.

I remember reading somewhere that another down side to set screws is they create pressure points on the barrel.


Whoever wrote that has an interesting out looks on structural stresses. The tapered pins are pressed into the barrel and gas block. If they think that there is no stresses on that setup… I don’t think I could convince them of anything else.


The best counter argument to pinning or dimpling a gas block would be what LMT does on some of their rifles. LMT machines the barrel with a gas block in it. They also do this with the bolt carrier and the gas key. No more bolts or staking.


This is a quote from another forum from a guy who works for ADCO:

"The blocks that are pinned on with tapered pins that wedge against the barrel or the slip on type of block with set screws that push up from underneath (or directly on the barrel) can deform the bore inside of the barrel and can wreck the accuracy of an otherwise great barrel

The clamp-on gas blocks avoid creating a stress-point on the barrel. The pinned blocks don’t actually “deform” the barrel but instead create a stressed area which can impart a “bump” in the bore and/or alter the barrel’s response to the shock wave of the bullet and gasses passing through it.

Match-grade barrels are usually completely (or as close as they can get them) releived of any stresses created by the boring and rifling processes. Most top 'smiths do everything they can to prevent any outward stresses being placed on the barrel when mounting in the chassis. "


I misunderstood the quote ,originally. Obviously.


Very Nice work.


Thank you Brother!


What is your opinion on adjustable gas blocks? I feel like they might be more prone to failure , is there any reality to that thought or am I off on that? I have never really had any gb issues to base my opinion on.


I feel that they have a place. That place is not on a defensive rifle. On a range toy yes. On a rifle for first time shooters to help with felt recoil yes.
Having said that there are people who have found the gas setting that works and have used a high strength thread lock and have run thousands of rounds with no issues.

There are always exceptions to the rules, or a counter argument.


Attention to detail! :+1: