Newbie here.
Wanted to thank the folks in this thread for all the information regarding the tube removal and install.
Just got a M4 and it was stupid easy to remove the OEM tube on mine.
Heat gun on low setting (450 F) and I only had it on the receiver for like 2 minutes as I wanted to test if it would move at all and it turned just using my hands.
The red lock tite didn't even melt but pretty much crumbled off. 99% of it was on the tube threads and basically nothing on the receiver threads.
Wiped off all the crumbled pieces and the new tube (DMW) went on easy.
Also, DMW tube is great! Got it in like 4 days after ordering on his site and while it may not be as nice as the FFT, CC or Briley, for 115 bucks, you can't beat it and he actually had them in stock.
I'm sure the titanium tubes from FFT (honestly think they are way over priced) and CC (reasonably priced but 3-4 month wait) are nice but DMW tube is exactly what I wanted at a price that is very reasonable.
For any other newbies like me, here are the parts to make it 922r compliant.
DMW tube - 115
DMW follower - 19
FFT forend - 70