Hello, I am new to the forum and T91s.
I just ordered a 16" upper which is on its way.
I have two questions:
(a) Does the T91 use the same bolt as an M16/AR15 (just the bolt - not the carrier)
(b) Any issues using a A2 stock with rifle buffer?
Thanks.
New to Forum and T91 - I have 2 T91 Questions
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apex
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I would not recommend using a rifle-length buffer tube on a T91 without using an anti-tilt buffer. The rifle buffer tubes do not have any countermeasures for carrier tilt, and you may end up wearing out your tube prematurely. On top of this, no one makes a rifle-length anti-tilt buffer tube, and POF/PA only make carbine anti-tilt buffer tubes.
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apex
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All AR models and derivatives suffer from some carrier tilt irregardless of carriers or buffer tubes. This is due to a combination of the geometry of the carrier and the gas acting on the gas key as it's funneled into the piston chamber allowing the carrier to travel rearward before the gas expansion actually occurs in the chamber. This simple force combined with the geometry of the carrier allows it to "seesaw" (for lack of a better term), as all the weight of the carrier is split between the two ends, while the point of "impact" of is effectively in the center.
This problem is negligible in DI ARs, but is a serious problem in piston ARs due to the piston being a much faster and more violent action. If you look at other contemporary short-strike piston designs (SKS, AR-18, G36, VZ-58, etc) the carrier's central mass is directly inline with the op-rod and piston to prevent aggressive tilting while traveling rearward down the guide rod(s) during cycling. The AR carrier is also free-floated and effectively has no guide rod, nor is it directly mated to the recoil spring.
Some piston AR developers have created workarounds to the carrier tilt problem:
Adams Arms, and the 205th taper the rear of the carriers to allow some tilt before the carrier is "corrected" by the buffer tube.
POF created and patented patented "carrier cradle" buffer tube so the carrier has no room to tilt and is no longer fully-free-floated.
LWRC and HK both taper and beef up the rear of the carrier to created a better seal inside the buffer.
All of these different designs are ways of mitigating carrier tilt, but none actually eliminate it. Even a nippled buffer does not completely eliminate tilting. Solving this would require a complete redesign of the upper and recoil assemblies.