03-16-2020, 05:43 PM
(This post was last modified: 03-21-2020, 05:49 PM by Hansel&Grendel.)
The inside depths of the buffer tubes do differ but is largely inherent to the design of the POF "anti-tilt" buffer tube that cradles (wraps around) the buffer detent. The external OAL of the POF (6-position) buffer tube and the SBA3 are virtually identical. However, the more I look at this, the differing internal architecture between the buffer tubes may very well be the issue given that all else is pretty much the same.
Granted, the AR 7.62x39 lower with the SBA3 pistol brace/receiver extension combo works flawlessly including LRBHO with its dedicated upper, but not with the 6.5 Grendel upper. Gas pressures are obviously different. So, I'll order another POF anti-tilt buffer tube that I can use for another build if it isn't the solution; and I'll play around with the various buffer/buffer spring combos.
The differing bolt catches just don't seem to be at issue but I'll eliminate any potential issue as I go along.
It's an intriguing issue and a sincere thanks for all the responses.
UPDATE: Replaced the buffer tube with an Aero Precision enhanced buffer tube. Still, no joy for LRBHO. Replaced the ST-T1 and JP Tuned Carbon Buffer Spring with a DS Arms 3 oz carbine (steel weights) buffer and another JP spring (mentioned in the original post) and was able to achieve LRBHO. I then found the sweet spot (bleed-off) for the Superlative Arms AGB. So, it appears that the issue was with either the ST-T1 or the JP spring. The good news is that it's working as it should for LRBHO. Happy end user who picked it up today.
Granted, the AR 7.62x39 lower with the SBA3 pistol brace/receiver extension combo works flawlessly including LRBHO with its dedicated upper, but not with the 6.5 Grendel upper. Gas pressures are obviously different. So, I'll order another POF anti-tilt buffer tube that I can use for another build if it isn't the solution; and I'll play around with the various buffer/buffer spring combos.
The differing bolt catches just don't seem to be at issue but I'll eliminate any potential issue as I go along.
It's an intriguing issue and a sincere thanks for all the responses.
UPDATE: Replaced the buffer tube with an Aero Precision enhanced buffer tube. Still, no joy for LRBHO. Replaced the ST-T1 and JP Tuned Carbon Buffer Spring with a DS Arms 3 oz carbine (steel weights) buffer and another JP spring (mentioned in the original post) and was able to achieve LRBHO. I then found the sweet spot (bleed-off) for the Superlative Arms AGB. So, it appears that the issue was with either the ST-T1 or the JP spring. The good news is that it's working as it should for LRBHO. Happy end user who picked it up today.