AR15 receiver extension removal

[Noban]

I'm about to really apply some torque to the receiver extension on my bushmaster lower to remove it. It was screwed in at the factory without grease and is realy stuck. I have the receiver clamped in a vice using one of the hard rubber inserts into the mag well, and I've applied Kroil liberally to the threads.

I think I'm going to have to really lean into this to break the threads loose. Should I be at all worried about deforming the receiver?

Thanks

Kev

 

[gamachinist]

Imho,
If it is stuck that badly,
You may damage the mag well putting all the torque onto it by clamping on a block.If I tried that,I know it would rip the side of the mag well out, :banghead:
but you may have better luck than I do!
I would strip it down,and try the freeze heat cycle that some people recommend on the barrel nuts:
Toss it in the freezer long enough for it to get good and cold,then remove it and heat the reciever with a small torch,hopefully expanding the aluminum,then put some more Kroil on it,allowing it to soak in.It might unscrew with minimal pressure.

If it still won't come loose,try the freeze cycle again,and it might just unscrew.
Best of luck,Robert.

 

[Noban]

Thanks, Robert. The insert for the mag well is sold by Bushmaster specifically for this type fo work. It inserts and snaps into place just like a magazine, so it's a pretty tight fit.

I have since spoken with a Bushmaster gunsmith and he assures me that what I am intending to try is exactly what they do to remove extensions. He noted that I shouldn't worry if I notice the receiver flexing under the torque, that no harm will occur.

 

[Sleeping Dog]

He noted that I shouldn't worry if I notice the receiver flexing under the torque, that no harm will occur.

Did you get that in writing, is there a guarantee?

I put my receiver in a book to protect it, then put the book in a vise. Then applied the torque and it came out. But, I assembled mine some years ago, so I knew it was put in with about 37 ft-lbs, and no loctite. It broke free at about 40 ft-lbs.

Is it possible yours has loctite? If it's anything better than the "blue" stuff, it'll take some torching to heat it enough to unscrew, tricky business with a plastic extension.

Regards.

 

[Noban]

Bushmaster assures me that they do not use loctite or any other adhesive on the receiver extensions. The do however turn them in dry while military specs require lube.