I am looking to purchase an extremely compact SBR for Home Defense, and possibly to serve as a truck gun. There are four things I wanted to run by you gentlefolk for approval and input.

The rifle I've been looking at is the Robinson Armament XCR-L Micro, chambered in .300 AAC BLK. This rifle is so small it could easily be fired from inside a vehicle if need be, and with the stock folded you could even keep it in a bedside table. I love the ergonomics of the weapon, especially the bolt catch. It's basically a built-in ambidextrous Magpul B.A.D. Lever, so I can chamber a round with my trigger finger! The brass deflector is nice, as well as the non-reciprocating charging handle. A 7.5" barrel is exactly what I'm looking for, and .300 BLK is still quite capable in that configuration. Just to make sure, ".300-221" is .300 BLK compatible, right?

http://xcr.robarm.com/xcrl.php

As far as sights were concerned I decided I wanted to keep it simple and go with some Troy Industries Micro DOA Tritium BattleSights. The Micro Set was designed for weapons with higher top rails, and the XCR is listed as one of the compatible platforms. They're nice and small, and the magic glow stuff is pretty cool too. The wonderful world of optics is too scary and foreboding for me, so I think I'll stick to BUIS unless the overwhelming opinion of you guys is that a red dot/reflex is always better.

http://troyind.com/%20/battlesights/...-now-available

I wanna run some rail panels so I don't tear up my hand, and I think Magpul XTM Rail Panels are the way to go. I'm planning on getting enough to cover the bottom and both side rails. Should I get some for the top too, behind the front sight?

http://store.magpul.com/product/MAG410/174

Lastly, do all 5.56 magazines accept .300 BLK? Do you have to fiddle with the feed lips or mess with the spring assembly? I was thinking of using either Troy BattleMags or Lancer L5 AWMs. Do you think those would work, being polymer and all?

If you're still reading, I truly appreciate it. If you have any advice at all I would love to hear it, I have so much to learn. Thank you and happy holidays!