I am buying an LMT SOPMOD stock kit to replace the standard collapsible stock on my RRA Entry Tactical. I attempted multiple site searches looking for information on removing the RRA tube but did not have any luck.

I remember briefly looking at posts in the past where it was mentioned that RRA tubes were possibly loctited to the lower receivers.

Can anyone confirm or deny this and give me any advise on how I need to proceed with this?

Has anyone put an LMT SOPMOD on their RRA Entry Tactical?

I had to dremel off my castle nut.  Good luck.

Viseblocks+Cheaterbar. Stake the finished product.

Please clarify your problem: Are you having trouble removing the castle nut, or unscrewing the tube??

FALARAK +1 - I've never had probs either...

Put lower into vice.  Press down on buffer detent and  remove buffer and spring.
Using carbine wrench, loosen receiver extension nut.  Back the nut all the way to the end of the threads.  Now slide the receiver extension plate all the way back.  Keep an eye on the selector detent spring while sliding this plate back.  The spring could fall out.  Look into the threaded part that the lower that the extension tube threads into.  You will see a detent.  Depress this detent.  Turning the tube counter clockwise start backing it out of the receiver.  Once the tube is clear of the detent you no longer need to keep this depressed.  Continue turning the tube counter clockwise until it is free of the receiver.    Now you are ready to install the new tube.  Put the receiver nut and end plate onto the tube.  Start threading the tube into the lower receiver.  While threading on the new tube, be sure to keep an eye on the selector spring.  Make sure the spring does not get pinched between the lower and end plate.  When the tube reaches the detent in the lower you will need to depress detent and continue threading tube until it covers half of the detent.  The tube will keep the detent from coming back out.  Now slide the end plate up to the lower receiver while keeping an eye on the detent spring.  Now thread the receiver nut until it reaches the end plate and tighten down.  You will now need to swage the end plate into the nut to prevent the tube from backing out.  Replace buffer and spring.