This project is finally wrapped! After getting all the parts, making those which were specialty items and doing the assembly work, we finally got to test fire our new AR-10s. Since Steve had wanted these set up as 1,000 yard guns, we went with the smallest possible gas holes and adjusted from there. Initial size was .076", but our first trials resulted in some failures to pick up a round out of the magazine, and failures to lock open on an empty mag. This past weekend, we went up to the shop and reworked the holes to .082". Problem solved, and the guns are working fine now; locking open on an empty mag consistently and stripping rounds from a loaded mag properly. Since the normal gas hole diameter runs somewhere around .093", we knew these guns would be a bit lite in the gas volume department, but for this application, that's what we wanted. Have some pics to follow, detailing the work and the changes.
In the above pic, my fellow LCSA team mate Greg Meredith holds his AR-10 upper, in prep to opening up his gas port. Greg's normally an M14 shooter (one of the few left on the lines today) so an AR in any configuration is a departure for him!
Last edited by Kevin Thomas; 10-29-2012 at 10:55 AM.
One minor feature (but much appreciated by those of us who are aware of it!) that Satern puts on his gas gun barrels is a small dimple on the underside of the gas port. This corresponds to exactly 180 degress opposite of the gas port, and allows you to precisely position the gas block over the port for maximum gas transition to the tube.
Proof in the pudding. Test firing the guns from the bench to make sure the bolts would lock on an empty mag, and would cycle (strip) rounds from a loaded mag. These rifles will be used almost exclusively as single shots (single loaded for slow fire), but we needed to make sure that they were completely reliable as to function. Greg is in the grey sweatshirt, and that's me in the blue.
Reason I was asking Kevin. When I shot on the Navy team at Perry. We use to rotate the front sight down to make up on what we could not get from the rear sight. It was like fileing down the front sight on my old M-1a so your rear sight wasn't sticking up so high.
Attached are two of the mods that Steve did to our AR-10s to get us to 1,000 yards. The first is a hole drilled into the upper receiver, directly under the rear sight post to give it a complete run, making use of all adjustment available.
The second is a front sight base, actually one for the AR-15. There's a height difference between the two, with the AR-15 front tower giving the AR-10 considerably more range adjustment for 1,000 yard shooting. Sort of like Palma type rifles using an adjustable ladder front sight. Steve marks these to differentiate them from the standard product. He does some other work on the front post as well, adding a positive lock to the underside that eliminates any movement after it's been zeroed.