I had the occasion to put a new gas block on an AR-15 I’ve had for a while. I had a heck of a time pinning the gas tube to the block, despite having the proper punches. I had a sense of deja vu, as I’ve had difficulty driving these little pins in before. I’m using a bench block but the darn gas block won’t sit in it firmly. AR build gurus, what is the secret for installing these tiny things?

I use a hollow punch to start them into the gas block.


You can get a set at Harbor Tools.

I'd say it also depends on the particular roll pin and the particular gas block.

I've had some be quite frustrating, while others are almost too easy.

You may just have the perfect bad combination of tolerance stacking.

Is your problem getting the pin started? Or getting the holes lined up?

If the latter, the trick is to use a punch/pin that fits through everything to keep it all lined up, then you tap the pin in from the other side (and push it out)


(If this something obvious you already know, I apologize, maybe it will help someone else.)

I wrap the jaws of a vice grip in a few layers of duct tape.

Once you get the correct width set on the jaws, get everything neatly lined up and gently press them into place.

If needed, a few gentle taps with a hammer and punch to get them seated flush.


You can use the same method on the roll pin for the bolt catch, and trigger guard on the lower.

This will do it and save you a pile of cash.

https://www.harborfreight.com/...t-3-piece-62686.html

I have also had a gas tube with an incorrectly-placed pin hole. Not off enough that it was readily apparent, when lining up the holes to attempt to drive the pin; but off enough that the pin didn't want to go. Under closer scrutiny, the problem revealed itself.

Now that I am writing this, I can't truly remember if it was the gas block or gas tube that was deficient. In either case, this is a possibility that would cause trouble.

Thanks, I have all the right punches. Roll pin starter punches, regular roll pin punches. The problems are it’s hard to keep the gas block from moving when tapping in the pin, and I think some pins are just a wee bit too large for the hole. As mentioned above, tolerance stacking. I like the suggestion to use padded vice grips.

I put the gas block in a padded vice, the ends of the gas block against the vice jaws. Roll pin starter punch after making sure everything is aligned.

There are a number of jigs and blocks to help with specifically this task. Ranging in price, materials, features, etc.

I use this one, but it's not super universal in accepting gas blocks that aren't the more common, almost standard low profile.
https://www.forwardcontrolsdes...-Pin-Tool_p_218.html

Crush the end of the roll pin a bit to taper it.

I also suggest a roll pin starter/holder. Get ones that is the right size. Finish with a normal pin punch.

Thanks all for the great suggestions!

MILSPEC for the front sight\gas block is tapered roll pins installed from left to right IIRC. I gave up on that nonsense and just use regular split roll pins. I've removed\installed numerous front sights\gas blocks this way, and have never had an issue with anything coming loose.