Those papers are a treasure trove! Thank you for posting them.

(1) An arbitrarily large buffer weight could change the unlock time to any desired value. A large mass can have low velocity and still have enough energy to do the work. The low velocity delays the unlock time.

I agree that the available buffer weights can only delay unlock time by about .1 ms. Whether this is enough to have an impact on bolt life or cycling reliability is best determined empirically.

(2) There is no minimum cyclic rate (in a theoretical sense). Again, a more massive bcg can operate at lower velocities, and still have enough energy to complete the cycle. The lower velocities will lower the cyclic rate.

Compressing the recoil spring takes a certain amount of integral Force(x) dx = Work. Work has dimensions of energy. It's the energy necessary to exert a force through a distance. Velocity does not do work.

A mass could have a velocity of 1000 ft/sec, and lack the energy to lift a mosquito 1 inch. Another mass could have a velocity of .000001 ft/sec and still have the energy to lift the Empire State Building 500 ft.

Momentum does not do work. A mass with momentum of 1000 slug ft/sec could lack the energy to lift the mosquito 1 inch, if the mass was large enough.

Bcg energy is the relevant quantity, and enough energy can be had at lower velocities if the mass is increased.

I think the problem may be that the papers you reference do talk about the momentum of the bolt carrier. They use the momentum as a measure of energy. This is valid via E = p^2/2m,as long as the mass is constant. They are talking about a constant mass bcg, the M16 mass. We are talking about varying the mass.

If mass is constant, velocity is also a measure of energy (not a linear one). But again we are talking about varying the mass.

(3) You can probably anticipate what I'm going to say here. It takes a certain amount of energy (not momentum) to strip the round.

If I compress the recoil spring by an amount x past the relaxed length, the spring stores energy V = (1/2) k x^2, where k is the spring constant. If I then put a big or small mass ahead of the spring and let go, the spring will give this energy V to the big or the small mass. This will lead to a difference in velocity between the two, but not a difference in energy.

If the recoil spring has been fully compressed, a larger or smaller mass bcg will have the same energy at each point in its forward travel (but not the same velocity).

(4) Again a more massive bcg can operate at a lower velocity (10% lower according to my analysis above), delaying extraction time (by .35 ms or so, according to my calculation above) and thus giving more time for the chamber pressure to drop and the brass to cool and contract. This will reduce extraction force.

It looks like you are right about the flow in the gas tube being subsonic, except for a short length at the beginning.

Some of my statements above involve approximations to keep things simple, but I think the general conclusions are valid. Forgive me if I have belabored my points.

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