Cliff notes: Carbon upper and lower, gas PISTON, BCM 14.5" 1/7 pencil barrel pinned and welded, Troy free float quad, Geissle trigger, ;laser, optics, bipod=6.93 lbs
In case anyone is interested, here is what i did to my custom build based on a Bushmaster Carbon 15 new model with fwd assist:
BM Carbon fiber upper and lower, BCM 14.5" lightweight barrel 1/7 twist with an X-comp blind pin welded, Adams Arms LITE piston kit,Troy 2 piece free float quad rail modified to clear the AA piston rod rear spring bushing, Upper milled(thats right, milled) to accept lower retaining lugs on Troy rail, FDE ladders for the quad rail, milspec buffer tube and H2 buffer, Ambi safety, Troy ambi mag release, Badger Ambi battle charging handle, Magpul ambi bolt release(B.A.D.), Magpul flip up BUIS,roller cam on bolt group, Geissle 3 Gun Trigger, MOE Stock, Falcon Ergo Large pistol grip(changing to Magpul MIAD), Gripod used only as a deploy-able bipod an INDEX for my grip on the quad rail, ERT Hybrid Urban Sling convertible one/two point non bungee WIDE, six Magpul Maglevel 30 rnd mags and a few clamps for them, polymer dust cover.
The rail, pistol grip and MOE stock and rear sight are in FDE.
Optics: undecided: between a CRS 1x4 scope with ffp reticle and a Burris fastfire2 with a Burris 3x on a FTS QD mount. The CRS scope is hugely versitle and good to the limits of the carbine with its reticle. The Burris has NO aiming holds but is a MUCH lighter option escpecialy with the 3x on a QD mount.
I own a CRS scope. I will be mounting it tomorrow. its a BRICK at 16.5 oz PLUS a heavy Bobro QD. It destroys my light weight concept. I have serious hesitations about this.
I will post some pics VERY soon. Its complete except for the Bagder handle and the polymer dust cover. Onlyn issues I have is the bolt lock sometimes accuates when its not supposed to. I need a stronger spring is all. Other than that...flawless operation. My first ever build and my first AR15. I never touched one untill now. It was not easy with all the machining we had to do. Cripes just getting the Bushmaster gas block off was a palaver, even in a state of the art machine shop. Yes we torched it, froze it, etc. In the end...milling machine! No damage.
We did a very careful blind pin weld using a dial indicator to square everything and used HARDENED dowel steel. It WILL pass the BATF field test of a giant pipe wrench and the barrel in a vice. Measured lenght of the barrel using a dowel rod on the bolt face is 16.45 inches. That is the way the BATF measures them. That X comp is not coming off with ANY size giant pipe wrench that the BATF uses in the field. Guys who used a bit of soft coat hanger for a pin might want to reconsider their legality. Even a peice drill bit that some guys use as a pin could shatter(brittle). Please, use ONLY hardened steel like they use in taper pins. Argon gas Mig welding on top of the pin which sat 1.65mm below the surface of the muzzle brake.
Weight with no magazine and a small NC Star reflex sight and a poweful green laser and 2 BUIS, grip pod is 6.93 lbs. Everyone who handled is remarked how noticeably lighter it was than any other AR15 out of the 25 that were in attendance of our Thursday night shoot. I am VERY hesistant to commit a 1.5lb 1X4 on it. If I loose the laser and use only a Burris Fast fire it would go 6.5lbs or less.
My Midwest drop in quad rail was much lighter than the Troy but it was not free float and wobbled a bit. The Troy is free float and locks the upper reciver in place for a MUCH sturdier build. Light weight AR but rock solid. poo poo the Carbon all you want. I have NO hot gasses going back to it now. In fact the gun was never fired in DI gas. No carrier tilt that I can tell and the roller cam seems a big help. The Geislee trigger? Everyone should try a Geislle.
PHOTOS: I have a Magpul normal grip mounted. I will have the MIAD or the Falcon Large later. The laser is light and VERY powerful. I like to mount it on the top bore axis. It is completely out of the way of my BUIS and reflex optics, and less likely to get damaged or knocked out of zero in its present location. It is VERY useful for our night shoots on close and distant steel targets. Its worth keeping for its usefulness and light weight. No pressure switch on purpose.
DISCLAIMER: Reason my SAFETY is on FIRE: I dont store my guns with my trigger hammer cocked. I do have the magazine always removed (except for a photo) and a chamber flag in the upper receiver. Always out of sight in a case locked away. It was displayed in various atypical modes for photo purposes only. Out of habit the hammer was not cocked.