Buffer tube STUCK on my new JP?

[Smokin]

I bought a new JP SCR11 this month. Ordered it with a UBR stock, changed my mind and decided to change to a PRS. Well JP sent the new PRS which arrived today (Friday after they closed). Well I thought removal of the UBR would be pretty straightforward. Take the spring and bugger out. Did that. Take the UBR butt stock off. Did that. Then it came down to unscrewing the buffer tube from the lower. Damned impossible. Put a 5/8" wrench at the end of the tube, wont budge. Hit the threaded section with a heat gun to soften any loctite that might be there (dont know if they use locktite on this part- shouldnt need to), and tried the 5/8" wrench again. Wont budge. Then I tried a strap wrench, nothing either. Who has a JP? is this normal? I wish I could call and ask, but obviously they are closed for the weekend. Any ideas?

[Biloxi23]

Does the UBR use the carbine lower extension (buffer tube) 0r the rifle extension? I've never seen a UBR up close, but the bextension that are used ot mount an M-4 type stock have a plate with a tab that fits into a groove on the bottom of the buffer. This keeps the collapsible stock from spinning on the tube. The back side of the plate also has a raised area that fits into the lower receiver to stabilize it. Could this be your problem?

[Smokin]

No there are 2 Tubes essentially on the UBR. The one underneath is a proprietary buffer tube (that's stuck). The other tube which the butt stock slides on, is attached via a screw similar to a rifle stock on an A2 with a screw at the end of the tube. The only thing remaining on the rifle is the "inner" tube.