About a year ago, I began experimenting with the Vltor A5 system. My rifle is a 16.1" DDM4 midlength gas, and I used the A5H2 buffer and mil-spec action spring that came with it. Both suppressed, and unsuppressed, with a variety of ammunition, I felt that the function was very smooth. Follow-up shots were honestly faster, and recoil was perceived as less.
The first carbine course, however, that I took the rifle to, I began to get malfunctions once the magazines got dirty. Specifically, the BCG would fail to fully strip a round from the magazine on reloads, or the BCG would fail to fully seat having stripped a round. It was never an issue that presented during live fire, but only on reloads. Still, it irked me.
Today, I cleaned my rifle, and lubricated it lightly with Weapon Shield. The BCG is a Fathom Arms QPQ'ed BCG with a Colt ejector spring and a Ken Elmore "Green" extractor spring (of note, some failures at the course I attended involved the round not fully leaving the magazine, removing "over-spring ejector/extractor" from the equation as the culprit).
I brought two lowers with me. One is a factory DDM4 lower with a Sprinco Blue spring and H buffer, and one is the factory DDM4 lower using a Vltor A5 with H2 buffer and mil-spec spring. After I got home, I measured the spring. It is exactly 12.5" long, which is directly in the middle of the specification for a M16 action spring. It has roughly 2,000 rounds on it, and had less than 1,000 when I first began having issues.
During my testing, I had 3 failures with the Vltor A5 system to fully strip and seat the first round in the magazine. Two of these are seen in slow motion in the videos to follow. Using the Sprinco Blue spring, and H buffer, shot-to-shot was a bit more "bouncy", and there was more muzzle-dip upon dropping the bolt on a fresh magazine. Of note, all initial shots show the bolt-release being depressed (fully and swiftly), and the magazines are fully loaded G2 PMAG's. I will let the following videos speak for themselves, as I use IMI MK262, PMC Bronze .223, and Wolf 55gr Polyformance to demonstrate how each performs with each action system, both suppressed (Surefire 556-212) and unsuppressed (-212 FH).
Wolf Polyformance 55gr .223 w/ Vltor A5:
Wolf Polyformance 55gr .223 w/H buffer and Sprinco Blue:
PMC Bronze .223 55gr w/ Vltor A5:
PMC Bronze .223 55gr w/H buffer and Sprinco Blue:
IMI MK262 w/ Vltor A5:
IMI MK262 w/H buffer and Sprinco Blue:
Vltor A5 failure to chamber fully: