ar-15 gas block

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Jul 31, 2010
How difficult would it be to take the standard front sight/gas block of a an ar-15, and replace it with a low profile gas block? Would this require a gunsmith or any specialized tools?
Is your present fsb/gas block pinned in place? If it is, it could be easy or it could be hard. Some of those pins are pretty stubborn. In any case, look at them and determine is one side of each pin is larger than the other in diameter. You'll want to knock them out from the smaller side toward the larger side. If you have a muzzle device, you'll need to remove this. The block should just slide off.

Most low profile gas blocks are held in place by a set screw, so all that will be needed will be to slide the new gas block on, position it and tighten the set screws; although the best way to do it is to dimple the barrel so that the set screws won't slip.

The easiest overall way to do it would be to cut the fsb into a low profile gas block. A few mintues with a hack saw and dremel tool and some alumahyde should have you where you need to be.

You can do any of the above with common tools.
I don't currently have an ar-15, but I am looking into buying one. I want a completely flat top, but some of the flat tops still have a front sight sticking up. If I could get a better deal on one with a front sight, I didn't know if I could remove the sight.

Thanks for the help.
It depends on whether the weapon has a muzzle device that has been pinned/welded in place or is simply screwed on.

You will need a taper pin starter punch, a set of barrel blocks, a good stout vice, a wrench to remove the flashider if it is screwed on or a lathe to cut through the pins and welds if it is permanently attached.
You will also need a big farking hammer to go along with the taper pin starter punch.
Brownells offers a bench block to hold the front sight/gas block assembly as you drive the pins out or in, it is another way to go.
I have one, they work very well but are also expensive.

You will need a center punch to mark the securing screw locations on the barrel for the low pro gas block and a drill press and bit to punch the screw divits on the barrel once the locations are marked.

Whether the job requires a gunsmith is dependent on your personal skillset.
With a Brownells bench block, and the right punches and mallet, it's an easy job. Without them, it can be a nightmare.
make your own. go down about 2/3 of the way

also, I made sure mine had no front sight when I bought it, thinking "I'll mount my optic lower now that the front sight is out of the way" but you can't get your head down low enough to the axis of the bore if you mount low. Turns out there's a reason the sights are jacked up so high.
Thanks for the heads up and advice. The whole reason I wanted to only have the gas block was so I could mount an optic lower. So that may have just threw all of my plans out of the window.
Depending on what type of optic you're using, you probably won't have problems with the front sight post.

If you're using a 1X optic (Aimpoint, EOTech, etc), seeing the front sight post is a matter of preference and there are different mounts to deal with this. A true co-witness (the line of sight of the optic passing through the line of sight of the irons) is still functional, and many shooter prefer this. A "lower 1/3 co-witness" mount will raise the optic some, so that the dot floats above the line of sight of the irons.

If you're using a magnified optic, you probably won't be able to see the front sight at all, except for at low magnification. And even then, it appears as a blur that is easily ignored.

If this is for a range rifle, plinker, etc. that you don't need back up iron sights for, there is no problem with grinding down the FSB. Lots of folks do this too.
Ok, thanks for the info. I plan on using a magnified optic on this configuration, but in the future I think that I would like to buy several different caliber uppers for it. I would probably use a couple different types of optics. I will try to try a a few different configurations before a buy one, to see how it works.

I plan to use this rifle mainly as a fun gun, and maybe some hunting with a 6.8 spc or 6.5 upper.
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