So a friend of my fiancee has asked me to help him install a railed handguard on his AR.

He has this: https://www.stngrusa.com/ultimate-hwk-m-lok-bundle/

I've got an upper receiver block, a vise and a torque wrench (and an AR combo tool). Will all that be sufficient for this job?

Do I need some anti-seize as well?

Seems straightforward enough, but the only unknown to me at this point is what sort of gas block he currently has on the rifle. I suspect it's a standard A2 front sight/gas block. It's a rail gas block. Looks like it might be roll pinned on? Am I good with just some pin punches and a hammer here?

Built plenty of lowers before, but never touched an upper.

I don't use anti-seize, just a good high pressure grease (I usually use Lucas Red). I've never had a barrel nut seize using it.

As for the gas block - If it has a standard A2 front, check to see if it has taper pins, find the smaller side of the pin and knock them out. Brace the barrel / FSB on a piece of wood. Don't be afraid to knock the hell out of the pins, sometimes it is necessary. Remove the muzzle device before you knock the pins out.

I prefer a reaction rod vs. an upper vice block, but it should work.

If the current barrel nut was installed without lube or with too much torque you can damage things trying to get the nut to break free. Try a bit of heat or something like kroil if you can't get it to break free without a ton of effort. I've seen receivers crack, barrel index pins shear, barrel index pins gouge into the upper, or the barrel extension loosen, any of which will pretty much scrap one or both parts. That's why a reaction rod that indexes on the barrel extension, but also distributes load into the upper receiver is the best tool, the Midwest Industries tool is one of the best for barrel work.

Similarly, the gas block can be carbon-locked on depending on how much leaking it had, how many rounds have been fired, etc. Again, a bit of heat or some carbon penetrating oil might be needed. If there are set screws they may have red loctite, which needs heat to loosen.

On the handguard you linked, the barrel nut doesn't need timing and comes with the right wrench. Lube the barrel extension lightly, use some decent grease on the threads (Aeroshell 33MS/64 is the military spec'd anti-seize grease), and torque to the specified value from the handguard instructions. Then loosen the nut, torque again, loosen, and tighten to proper torque for a third time (some recommend 5 times) - this will ensure the receiver and nut are properly mated and "seasoned" so the threaded joint doesn't relax and allow the nut to loosen in the future.

Edit:
You'll be changing the gas block as well. The gas tube can be salvaged. The most important item with the gas block is aligning the gas port in the barrel to the port in the block. Some blocks are made to not index off the journal shoulder, to allow a handguard endcap to be installed. I would check the gas block by fitting it first upside-down to see where the set screw bore is aligned with the gas port, you know the gas block port is 180° from that, and you can check spacing from the journal shoulder. There are several tricks to getting the ports aligned. If the barrel is nitride finished the set screws will have a heck of a time biting into the surface to hold. I would recommend dimpling at least one (the rear one), and using red loctite on that one.

Edit2:
While it doesn't need timing, looking a little closer, there is a small index tab on the lock plate that sets the hanguard in position relative to the barrel nut. If you get it installed and there's too much gap between the receiver and top of the rail, repeat the barrel nut torque procedure at a higher torque to seat the nut a little deeper to help close the gap (most barrel nuts have a torque range like 35-80 ft-lb, some just like a single 50 ft-lb or something similar, you can go a bit higher if they only list a single value)

Be patient and methodical on the removal of the gas block.
It could come off just fine or it may be hard, very hard.
I have had it where it had to be heated and drilled out - a real bear.
Thankfully all I install is on new barrels so I don't have to deal with it much.
Good Luck.

I wasn't able to get to his upper this weekend, but I did look at the rifle. It's a S&W carbine of some stripe.

The S&W gas block is on with a cross pin of some sort, probably a taper pin.

My concern now is that the barrel is not dimpled for the set screws that come with his new low profile gas block, and it looks like the barrel is Melonite finished.

If that's the case, I think that's beyond my capabilities to dimple for a set screw. He's OK if we tear it apart and can't complete the installation, but I feel like that shortchanges him a functioning gun, even though he'd be out one anyway in the time it takes for a smith to do the job.

quote:

I think that's beyond my capabilities to dimple for a set screw

Set the gas block up and hold it in place with blue tape for a few minutes while you find a drill bit that is smaller than the set screw holes.....use just the drill bit(no drill) and twist the drill bit to mark the spot it needs to be....take everything off....use a drill to lightly dimple the spot aforementioned....GTG.

Why do you need to dimple for the set screws? If the gas block is under the rail, it's not going to move.

I've got a couple that way, including one used hard in rifle and 3 gun matches for a long time. Never any problem and the idea that I needed to dimple the barrel has never crossed my mind, to the point where I was confused reading your post. lol

Maybe for your competition rifle you don’t care. But I have never seen anyone recommend a do nothing strategy in this area for a serious gun. The minimum I would accept is a cross drilled pin. I would prefer taper pins x2. Dimples set screws is beyond easy so why not do at least that. It’s way better.

quote:

Originally posted by hrcjon:
Maybe for your competition rifle you don’t care. But I have never seen anyone recommend a do nothing strategy in this area for a serious gun. The minimum I would accept is a cross drilled pin. I would prefer taper pins x2. Dimples set screws is beyond easy so why not do at least that. It’s way better.

Set screw alone is fine under a HG. Once you have a few hundred rounds through it, the carbon buildup will have it set so tightly it won't move with no fasteners in it.

quote:

Originally posted by hrcjon:
I would prefer taper pins x2.

Did you look at the gas block? 


Also, I have a "serious" AR and I will never in my life do to it what I've done to my match rifles in terms of use and abuse.

Of course I looked at the gas block. Which is why I suggested they at least dimple the set screws. Which is beyond simple, takes less than 30 seconds and improves the situation dramatically. I don't agree with the MikeinNC strategy for doing that, install the gas block properly, remove one screw (this one has two) dimple, install that screw remove second screw and dimple that one. Tape isn't a necessary part of this. As for relying on set screws and carbon buildup in general I don't have the ability to test durability in volume so I rely on others who do. And those include the people that mfg my barrels and handguards (always include and recommend a cross pin) and the decisions by people who actually issue these guns to soldiers. I am unaware of any issued gun that relies on set screws alone. There might be some and I am willing to learn that its a better method than I think.