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Thread: 24" 6.5CM AR-10 (upper build)

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    24" 6.5CM AR-10 (upper build)

    Really just an upper build, since I swap my uppers around on my Aero M5 lower (all .308 to-date). Upper is built on an standard Aero M5 upper, lapped the front receiver face, tried to shim the barrel extension with .001" shim stock, but the receiver bore was too tight, didn't want to resort to heat since I do disassemble every now and then. So I test fitted the barrel with several of the M5 uppers I had on a shelf until I got the tightest fit. It's tight, but barrel can be pulled out of the receiver with some effort. De-burred the barrel extension feed ramps and also the edges of the BE lugs to help the bolt lugs to slide in. I also used one of these small green rubber abrasive dremel tips to smooth out the lower edge of the feed cone, followed up by a felt cone with polishing compound, but that was done after the pic below.

    for the gas port, I measured the distance from the gas port to the shoulder edge, similarly for the gas block (SLR Sentry-7 adjustable, clamp-on), measured the gas port diameters, and then calculated how much, if any, the gas block needed to be spaced from the shoulder so that the hole in the GB is dead-centered over the barrel gas port, came out to .015". Used feeler gages to get that spacing. FWIW, the gas port for this Faxon barrel is .072".

    Completing the upper is a Brownells HP 308 nitrided BCG ($133) and it has the skinnier firing pin (HP, compared to normal 308), and smaller firing pin hole in the bolt face. Checked the headspace using Forster HS gages, GO and NO-GO, checked out good. Using an Armalite AR-10 rifle-length gas tube, because the regular AR-15 rifle gas tube looked a little short extending inside the receiver, no, it doesn't bottom out in the gas key. Painted the gas tube flat black, hi-temp engine enamel. SLR Solo Lite 16" KM handguard, I like KM, saddened that it's going away, so I'm stocking up on BCM KM pic rails (and also KM sling swivel sockets). Rainier Avalanche charging handle, my favorite ambi. Brake is a VG6 "65" Gamma, specifically for the 6.5, .264" caliber, 5/8-24. The exit hole is smaller (0.295") than a .30 cal brake hole. Brake is timed using Precision Armament shims, and also some left-over SureFire paper-thin 5/8" shims, I like to go pretty light on the MD torque, usually the minimum spec torque, to eliminate any possibility of squeezing of the barrel bore at the muzzle. Engraved ejection port dust cover is from CustomARDustCovers, special ordered, because I wanted "6.5 CM" inside and out, instead of "6.5 CREEDMOOR". I replaced the Aero-provided forward assist plunger with one from White Oak Armament, because the Aero piece doesn't reach over enough to engage the bolt carrier serrations (although the take-out FA works just fine when re-purposed in an AR-15).

    Optic is a refurbished Viper PST Gen I FFP mil 6-24x, with a Switchview/Vortex SV-2 aluminum throw lever (both from A&A Optic), in a AD Recon-S.

    Feeding & cycling was flawless right from the start, "economy" factory ammo from LGS, PMAGs and CPD 20rd steel mags. Gas block is set for 7-clicks open. I boresighted in my house to get the scope in the ballpark, 17 yds hallway-to-garage-wall. Using the mil-reticle, watching the dirt splashes, dialed the scope in "close-enough" using a dirt mound at 100yds, then got onto 600yd steel silhouette with 3 more rounds. That was awesome (for me anyways, probably ho-hum for everybody else on here).

    Lower is Aero M5, Geissele HS-NM with KNS Gen-G pins, KAK 5.3oz 308 2.5" buffer, Slash/Heavy-Buffer 308 carbine buffer spring (my go-to), Norgon ambi, POF AR-15 carbine buffer tube, B5 Bravo stock.



    mockup to check fitment, please ignore grease.




    Last edited by rpoL98; 12-06-19 at 17:09.

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