Gas fed or piston drive is a hot

This project was undertaken to see just how small a 6.8 spc II could be built without custom fabricated parts. Did not wany to chop a barrel or any machine work but the pistol brace was shaved to minimum size to fit buffer. For this AR pistol build I chose a Battle Arms Development's ULTRA COMPACT PISTOL SABERTUBE® and VERT® BUFFER SYSTEM COMBO with KAK green stabilizing brace, Superlative Arms pistol length piston kit and a Bison 7.5" 1:7 fast twist 6.8 barrel as the heart of the build. As is common for my builds a Fostech/Mag Tactical billet magnesium lower combined with a SIG upper were selectd as the foundation. The forearm is a 7.5" Gorilla Machine which is one of the fairest priced U.S.A. made models have found and works very well. It currently sports an inexpensive red dot sight on riser that is a 1/3 cowitness with the iron sights. More to come on this AR pistol build including range report and video.

7.5" BISON/SUPERLATIVE ARMS PISTON BUILD

MOCK-UP & DEVELOPING A PLAN

Often a build is so straight forward the smith can just dive into the job. The scope of this build required two separate mock ups to determine best forearm, pistol brace and modifications needed before the actual build process began. This was the first use of the Battle Arms Development buffer kit and wanted to use a Tailhook pistol brace but every place I checked was out of stock including the manufacturer so with some trial an error disobevered that a KAK Shockwave brace had enough meet to trim front almost to attachment screw and the rear without losing the sling attachment or slots for brace straps if choose to use them. This atually came out a reasonable one hand pistol. The shine of the stainless barrel was obvious the Cerakote HVLP would have to come out.

SUPERLATIVE ARMS PISTOL LENGTH PISTON KIT

ASSEMBLY OF PISTON KIT & FOREARM

On this build it was mocked up three times while decided which parts worked best for build. Tried three different forearms which meant three different barrl nut types with appropriate torque wrench adapters. idn't take long to determine I needed to Cerakote the Barrel O.D. Green to match the other accessories. If you cant buy or borrow a minimum $49 Craftsman torque wrench and hold the upper while torque items like barrel nuts and muzzle devices to proper values then buy or borrow one.

USING WHITE OAK ARMAMENT HOLDING FIXTURE TO INSALL BARREL WITH TORQUE WRENCH

As mentioned a foot/pound torque wrench for installing barrel nuts and muzzle devices, an inch/pound wrench is needed for gas blocks. The clamp on Superlative Arms piston kit gas block calls for 30 inch/pounds on screws. Many gas block leaks and broken mounting screws are directly linked to under or over torquing of fasteners. It is a myth that a properly built gun can be done on your kitchen table with a universal armorers wrench. I use at least three different holding fixtures in the assembly of most AR 15's and two or more torque wrenches. Use a Craftsman for first runup of barrel nuts but when time comes for final torque after threads relax due to streathing usually swap to a calibrated CDI or Snap-On.

SELECTING & INSTALLING TRIGGER

After several mockups finally arrived with parts that all complimented each other and was just missing a fire control group. Chose a Colt Competition Target trigger which was squared and honed using a Power Custom Hammer & Sear Jig. Used the factory springs to ensure reliable ignition and not drop trigger pull too low for an AR pistol. Trigger scale measured this trigger when finished and installed right on four pounds even. After final assembly followed the clearcut instructions that came with the Superlative Arms Piston Kit and the short 6.8 was over gassed taking almost two turns to calm it down till had perfect ejection of brass screwed on a suppresser and with a little tweaking found a setting where brass landed in the sweet spot suppressed or unsuppressed with an AAC 762SDN-6 mulitcaliber can. Considering size, cartridge and combination of parts used this gun has very manageable and comfortable recoil. Honestly I can't wait to do another an see if can build another full power AR even smaller. It is supriningly accurate and while adjusting suppressor actually had a ground hog appear about 60 yards away and took it with a single shot.

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