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Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Sat Aug 26, 2017 9:32 am
by giannid
So I've read some threads about removing the old handguard off the upper. Is it necessary to change the barrel nut also for a new handguard? I know some manufacturers use a proprietary nut for there handguard. Any special tools needed to take the oem nut off the Bushmaster upper?

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Sat Aug 26, 2017 6:11 pm
by Bmt85
I believe it is proprietary, so chances are you can't swap something else on the factory barrel nut. I can't remember how to remove, but I want to say heat and a wrench similar to what you would use for an automotive oil filter (a cheap one probably won't hold up). Never tried it myself, so can't say for sure.

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Sat Aug 26, 2017 7:48 pm
by giannid
People are definitely changing the handguard on these so they must take a barrel nut from another manufacturers handguard. Hopefully someone who's swapped out hand guards will chime in. I'd like to put on a midwest rail.

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Sun Aug 27, 2017 10:05 am
by Bmt85
That's what I said, but I don't think I was very clear.
The threads for the barrel nut on the factory upper is standard. The threads on the barrel nut for the handguard are not. So to install a different handguard/rail, you need to remove the factory handguard AND the barrel nut. After that it's a standard install.
Good choice on the Midwest handguard, I run a couple different ones, and I am currently running a 15" LWMG3 on my 450B. Love it.

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Sun Aug 27, 2017 2:34 pm
by giannid
What do you use to remove the factory nut? Is it anything special?

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Mon Aug 28, 2017 9:55 am
by plant_one
an ar15 barrel nut wrench is commonly used to remove them. a standard ar-15 armorer's tool will have it. its just pins that go into the holes for the gas tube at two points.


https://www.midwayusa.com/product/77384 ... r-15-steel

thats what i have, but there are many many variety's of armorer's wrenches out there that will work.


you'll also need a vise block of some sort to hold the upper while you're torquing that barrel nut off, as well as installing the new one.

if you dont have them already, might as well jump on a kit and just be done with it. if you're gonna play ar-15 builder, you're gonna need most of this stuff eventually

https://www.midwayusa.com/product/49133 ... ntials-kit


at the very least you'll need the following

armor's wrench multi tool
torque wrench
vise block

the gas tube alignment tool is also a huge bonus for ensuring your barrel nut is properly aligned when you're torquing the new one on.

dont forget to put a little anti-seize on the threads when you put the new nut on too. dissimilar metals and all that.



also be warned - its VERY easy to blow out a gas tube hole in those factory style barrel nuts - thats just milled aluminum. as long as you keep the tool square, and fully inserted against the barrel nut you'll be ok. i found this out the hard way. as a precaution try to use the holes that are not near the 12-o'clock position when you do put the barrel nut wrench on there.




you *may* also be able to remove it with a strap wrench, but thats iffy at best. bushmaster is known for using locktite in places we usually dont want to deal with it - including these barrel nuts. a strap wrench will be handy though for removing the handguard from the barrel nut as they do use loc-tite to secure that connection and time the handguard.


hth

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Mon Aug 28, 2017 10:01 am
by Hoot
giannid wrote:What do you use to remove the factory nut? Is it anything special?


I used an AR15 Armorer's Wrench. Very important to stabilize the upper receiver before reefing on the barrel nut, so as not to distort it. I'm a big fan of the Block Worx system because it supports both sides of the receiver when clamped in a vise. You can do chin-ups on the Armorer's Wrench and not hurt the receiver. Start at 1:45 in video. I believe that These guys are the distributors for them. Remember a tool investment will last a lifetime if properly cared for. I still have a few tools I bought 50 years ago with my lawn mowing money. Still going strong.

Hoot

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Thu Aug 31, 2017 3:30 pm
by pauleberly
Are you wanting to sell your 20 inch handguard? If so send me a P.M

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Thu Aug 31, 2017 7:59 pm
by Texas Sheepdawg
I want the hand guard off my 20" so bad. I just don't know what kind of strap wrench will work and I've never seen one that small. If I can ever get that heavy ass hand guard off, I'm going to lap the receiver and put a Mason hand guard on it like I've done to my other ARs.

Re: Changing handguard on Bushmaster 91702 20 inch?

PostPosted: Thu Aug 31, 2017 8:41 pm
by plant_one
hazard fraught has them. i think thats where i got mine from.