Advice on Removing a Tight Receiver Extension

[D.O.A.F.S.]

Looking for some tips/advice on removing a tight receiver extension. I'm looking to lighten up my sbr and want to swap out the Magpul UBR that's currently on it for a CTR. I have had no luck even with heating the receiver to loosen it up, ideas? I personally installed the stock years ago, it was torqued to 35 ft lbs with "NO" thread locker.

[wigbones]

You could hit the threads with some WD40.

[26 Inf]

Take the upper off the lower. Place the lower tail up. Dribble KROIL around the castle nut. Eventually you should see KROIL on the exposed threads of the receiver - by the buffer detent. Try to remove it then.

Before KROIL, I used PB Blaster to good effect in removing rusted/corroded parts.

Both should be available at a hardware store or industrial supply.

Other than that you may need to sacrice the castle nut and tube - dremel at angle in two places opposite of each other on the castle nut. Make sure the angle is step enough you don't contact the receiver - you may not be able to dremel the castle nut completely in two. If you are the patient type, apply the KROIL again, if not then try to remove the nut. The ide is you've weakened the nut enough to allow it to flex and move.

That's all I got.

Good Luck.

[ScottsBad]

I've never played with a Magpul UBR, so forgive my ignorance, but does the UBR use a castle nut? I don't believe it does.

Hang the receiver with the buffer tube down and put some penetrating lube where the tube threads meet the receiver threads. Let it sit for a few hours.

Put the receiver in a vise using an appropriate method. Use the wrench that was supplied with the UBR kit to turn the buffer tube counter clock wise. You may have to press the buffer retaining pin down at the same time if the buffer tube is notched.

If this doesn't work try heating the receiver and not the buffer tube to get a differential expansion so the receiver expands slightly while the tube takes time to catch up. While warming it try to turn the buffer tube... You could fill the buffer tube with ice and water to cool it while heating the receiver. Always use penetrating oil at the same time.

If you are at your wits end, you may consider clamping the end of the buffer tube securely in a vise (do not collapse it) and try turning the receiver instead. Put a piece of wood through the magazine well for leverage and gently try twisting the receiver.

Thats all I can think of right now.

[D.O.A.F.S.]

Thanks guys, unfortunately those are things I've tried. The ubr does have a proprietary buffer tube with out a castle nut. I'm at work now, hopefully with soaking overnight it will come loose in the morning. If it doesn't I'll cut off the receiver extension and split what's left in the receiver so not too damage the lower. I'd rather loose the receiver extension then the lower.

[MegademiC]

You got the stock off, right?

Id secure the lower, with firm padding and as much surface area as possible, soak threads in penetrating oil overnight, and take an impact wrench to the stocks rear.

If it destroys the lower, i doubt anything else would have gotten the tube out. Just my 2 cents.

[Smokin338]

What exactly is stuck ?? The one screw on back of buffer tube that holds the upper cheek rest part or the buffer tube itself to the lower ?

https://www.youtube.com/watch?v=RUXK_VntVB0

[D.O.A.F.S.]

Buffer tube to the receiver.

[Smokin338]

Mag block the lower and a strap wrench will do the trick... you were only suppose to hand tight the tube to began with.

[HeruMew]

You got the stock off, right?

Id secure the lower, with firm padding and as much surface area as possible, soak threads in penetrating oil overnight, and take an impact wrench to the stocks rear.

If it destroys the lower, i doubt anything else would have gotten the tube out. Just my 2 cents.

Agreed, but damn; busting a SBR'd lower would chap my ass in all the worst places.

ETA: In all reality, you could try everything short of destroying something.

Turn around, pull the UBR back on. SBR another lower.