Disclaimer: I know nothing about AR pistols but I've assembled plenty of rifles though. That said, please forgive me if my questions come across as sounding stupid.

If you're a P516 owner, I'd really appreciate your feedback.

What I'm curious about is the P516's buffer tube. I noticed that it doesn't use a castle nut. How is it secured to the lower? Is it loctited in place or just screwed in hand tight? If the former, what type of loctite; red or blue? I'm asking because I'm curious to know if the lower is compatible with the KAK or Phase 5 buffer tubes?

Secondly, how does the handguard come off and how is the piston gas block secured to the barrel? Set screws, pins, or cross bolts?

Finally, any issues with the 7.5" P516? I like the idea of a piston driven pistol. If it's problematic, I'll just build my own I guess using a standard pistol DI setup or utilize another piston system from Adams Arms.

BTW, I can't seem to truly determine Sig's 7.5" barrel specs. Is it chrome lined or melonited (gen 1 vs gen 2)? Also, what steel is used(4140, 4150, stainless)?

And if you're reading this and have no idea what a P516 actually is, see the picture below:

TIA for any guidance provided.