The Adams Arms gas piston upper arrived a couple of days ago, so the first thing I did was to take it apart to see what made it tick.
Compared to the previous project, the M4E2(economy), it has a mid-length handguard which covers the operating rod, but otherwise the same 16.1 inch barrel. At first I thought it was a medium-heavy barrel, but when I took the handguards off, I found the only real (and minor) disappointment of the whole project.
The bolt head is identical to the original AR15 concept, except there are no gas vent holes, no piston rings used, and a slight spring on the tail of the bolt to keep everything in a forward position. The bolt carrier has several differences, including redesigned glide pads, and a noticeable rounding of the bottom rear, to assist in getting the upper receiver closed despite the spring pressure that tends to push the entire assembly to the rear. This may also be the source of the "bolt tilt" mentioned by some sources.
After spending most of today getting the trigger pull down from 20 pounds to 11, it finally dawned on me that one of the trigger components might be the culprit. I put in another hammer and spring, and the trigger pull immediately dropped to a bit over seven pounds, with plenty of potential for Nanolube to continue to work its magic. I looked at the old hammer, and it seemed a much cruder forging than the new one. I had just grabbed parts from my stash, but that old one went into the trash. Trigger work can now continue as normal.
Here's the rifle so far. I'm still waiting on a titanium firing pin, rear iron sight, scope, and other minor items like sling and swivels. But at least I have enough to begin testing.
The handguards are not identical between top and bottom, and seem a bit flimsy. I can probably adapt a Midwest Industries cantilever-type quad rail handguard, but I'm not ready to make that investment, yet. The other piece of New Technology is the GG&G "install from the outside" rail on the bottom half.
I wasn't ready to take them at their word, so I removed the handguards just to see how the mechanism works. It's vey ingenious, but due to the variations in quality and design of handguards, you might achieve better results by removing it. Here's what things look like from the inside.
No heat shield in the top half, but there's no hot gas tube up there, either. The heat shield in the bottom is a bit flimsy, and the rail's toggle clamps scrunched things up a bit and pulled the heat shield out of its slots when everything was tightened enough. Your mileage may vary due to the type of handguard you have.
Overall, I'm impressed with the concept, and have a second piece of rail I'll try on the "glacier guard" handguards on the M4E2.
That's the project status as of now. If I don't find the time to fire it this week, next week for sure. I want to compare it to the accuracy of the M4E2, and then I'll put a PWS buffer tube on it, and test it again. That way I'll be able to tell if the increased rigidity adds anything to accuracy. In one sense, I hope it doesn't make much difference, one way or another. Otherwise, if it provides a significant improvement, I'll have to replace the buffer tube on all my AR15s.