bump

I believe Mr. Harold Waterman who was the chief M16A2 program engineer at Colt's built this for me. He also held the patent on how the identical round halves of the A2 handguards would fit into either a round or triangular handguard caps.

I agree. I'd have a couple of those.

"...I use A1s on my A2s & A4s but w/ A2 buttplates..."
All part of the original plan...

Don't see a stock length issue when you can easily exchange and A1 stock with an A2 as long as you have an A1 buttstock screw. Now the A1 stock material will not be DuPont Zytel like the A2, but what friggen difference does that make to 99% of us never falling on our rifles...? The A1 takes a paint job better as well...

Was not for range finding, just reading the dial number through a hole in the rear of the handle vs the left side in the final design.

Sorry this took awhile:
1:7 vs 1:9 rifling twist discussions and decision were not significantly influenced by the twist rate recommended for the M856 tracer.  First off, the M249 SAW, which was to be the 90%+ user of tracers, maintained the 1:7 twist. Rifle use was considered, but 1:9 was considered “good enough” for tracer. But what really had the dominate element was that the new tracer round was to be the new NATO “dim to brighter” tracer. And when we tested it in the daylight, one could barely see any trace when sighting through the rifle sights. Whereas in side by side testing, the then current M196 Tracer was the hands down “winner control,” in the eyes of the troops because your eye picked of the brighter trace much closer to the muzzle.
Another was the potential cost savings by significantly reducing the quantity of 20-round boxed tracer for rifle use as it was not used very much at all. And the ammo guys saw reducing the tracer load-outs in Landing Force ammo stored aboard amphibious ships as a way to reinstate the rifle pack-out of ball ammo (1680 per case) that was being displaced by just 800 rounds of M249 SAW ammo in the exact same size wire bound wooden crate. This 1680 vs 800 rounds (in the same cube) was also the reason a large element of our Logistic Command wanted the M16A2 to be semi-auto only—and they had significant program direction leverage as they were funding my Improved Service Rifle program.  So when I found the 3-round burst control trigger mech, and ran this up the flag pole and got it approved, this allowed the M16 auto sear to stay in the lower.

There are at least three or more major factors that doomed the M249 SAW in the Marine Corps. First and foremost was the dropping of the mandatory Division SAW Gunners Schools too soon after the initial fielding was completed.  Such Schooling should have remained in place. Second maybe was the total lack of linked blank ammo during the first several years of fielding for training which forced the very unreliable use of rifle magazines loaded with blanks so the SAW gunners could play war. But this caused SAW gunners to lose reliability confidence in the weapon.
Due to manpower issues, most fire teams did not have full four Marines it was designed for. And because the SAW and its ammo load was the heaviest, it was assigned to the lowest ranking junior guy the team. This was contrary to when the older fire team’s BAR man was the second senior guy in the teams—literally the assistant fire team leader. I also remember one newsreel from Iraq that showed a SAW gunner wielding a sledge hammer—again—the junior guy getting the heaviest load.
Another was the total lack of increased logistic transport capability, i.e., more jeeps and trailers, at the organic infantry company level necessary to support the new 27 LMGs in each company. I mean that replacing 27 rifles with 27 belt-fed LMG’s were never complemented with appropriate motor transport at the company or battalion level.
In reference to the M27, numerous articles addressing its strengths and weakness are out there for you to glean an opinion on. However,I found it very ironic that when we might have rightfully expected to see massed human wave attacks coming across the North Korean border, we dumped a belt-fed for a box magazine fed. But then you also had some died-in-the-wool M16 haters (with an agenda) that saw a way to replace direct impingement rifles with those using pistons. However, there were live fire and maneuver deadly training incidents with the SAW that were being blamed of the open bolt firing nature of the weapon. This led to SAW gunners being required to completely unload numerous times during individual, 2-man, and team rushes; and thus a “requirement” for a “closed bolt” automatic rifle that was inherently “safer” while on safe and loaded with a round in the chamber during fire and maneuver than the LMG was thought to be.