AR Front Sight Block & Flash hider removal

**WVneighbor** · February 26th, 2009, 01:27 AM

My friend has a Stag Arms Model 2 that he wants to put a red dot sight on. After a short discussion he decided he does not want to co-witness with the FSB. He also does not care if the FSB is cut, filed, mangled or destroyed in the process. He did purchase a gas block with a rail on it that he would like to install in the place of the FSB. He wants the option of some time in the future being able to add flip-up iron sights.

I have not yet inspected the specific rifle, but I'm relatively sure the FSB is held in by pins. Removing them doesn't pose any significant challenge.

The part I'm not sure about is removing the flash hider. It is my understanding those suckers are screwed on pretty tight. Is there a specialty tool required to remove it? Or will an appropriately sized wrench and some elbow grease work? Or are we talking a vise?

Does the crush washer need to replaced or can it be reused?

Regarding the gas block, is there any special voodoo chants or does it pretty much line up?

We are pretty much committed to doing this ourselves in the near future, unless wiser heads strongly discourage it.

I am relatively mechanically inclined. I do my own car maintenance to include all mechanical and electrical repairs. I've done everything from carb to tailpipe, crankshaft to pinion gear, master cylinder to wheel cylinder and everything in-between, so I know this task is well within my abilities.

Any suggestions, tips, or tricks would be much appreciated.

**Lycanthrope** · February 26th, 2009, 09:43 AM

The flash suppressor comes off with about 30ft/lbs of torque. I have friends who have wrapped blocks of wood in towels and then vised the receiver, but I use a plastic ar15 action block and a vise. Works perfectly. You can reuse a crush washer, but they are dirt cheap so I rarely do.

The gas block is a bit more tricky. When you take off the front sight base the gas tube will come with it (take off the handguards). Lube up the barrel hard so you can pull it forward and not scratch the finish. Then you will need to tap out the gas tube roll pin (I recommend buying another one of these in case you bugger it) and install the gas tube on the new block.

Setting the new gas block is critical, but not hard. The gas port in the barrel needs to align with the gas port in the block. The gas block port is bigger so you have some leeway for leveling it (if it's railed, you want it level with the receiever so you could mount sights on it). There is often a step in the barrel under the handguards and people want to push the gas block back into that shelf.....it will look like you should....but don't. The gas block holes will align perfectly if the block sits forward of the shelf a small margin (the gap is designed in to work with the regular handguards). I use calipers and do some math if need be.

Finally some gas blocks are pinned on, some are held by set screws and some are clamped on with screws. For set screw blocks I dimple the barrel with a drill press just a bit so that the set screw is recessed. Not necessary for a range gun, but it makes the gas block to barrel fit stronger.

Lycanhopethathelpsthrope

**egon12** · February 26th, 2009, 08:34 PM

I agree with Lycanthrope 100%, and I would like to add my two cents worth. If the front sight gas block is pinned on I would suggest that you add a bit of penetrating oil to the pins and let it sit for a few hours. It makes the job a lot easier. I have used Kroil with a lot of success. Also some of the pinned front sight gas blocks use a taper pin and can be only driven out one way and vice versa when installing. They need to be driven out left to right when you are looking towards the muzzle from the rear. Don't ask me how I know this because it is a long painful story. Good luck with your project.

**WVneighbor** · February 27th, 2009, 12:37 PM

Thank you gentlemen. As I said this is going to be a project to be completed at some time in the near future, so I've got times to get another crush washer and roll pin(s).

I'm going to check out YouTube to see if there are any demonstrations, but from the tips that have been posted I'm confident this isn't above my pay grade, so to speak.

Again, thanks for the responses.

**Kaos** · February 27th, 2009, 12:41 PM

Originally Posted by WVneighbor

Thank you gentlemen. As I said this is going to be a project to be completed at some time in the near future, so I've got times to get another crush washer and roll pin(s).

I'm going to check out YouTube to see if there are any demonstrations, but from the tips that have been posted I'm confident this isn't above my pay grade, so to speak.

Again, thanks for the responses.

I swapped a gas block without instruction or video on my first try on my first build. You should be fine.