Originally Posted by
Clint
These are some excellent points, so let's parse through them.
Its true; a light rifle will tend to move around more than a mid-weight rifle.
A brake tends to add a little gas drive, while a light weight reciprocating assembly requires less gas drive.
The combination of the two points to a smaller port size.
There are many factors to consider and we don't want to sacrifice reliability just to get ultra light recoil.
Again, the standard gassing is setup for full weight reciprocating parts with an A5 buffer.
Overly strong springs are generally not helpful with our barrels.
Yes, a strong spring can absorb more recoil energy, but then it returns more energy during counter-recoil, producing higher bolt closing speeds, more muzzle dip and bolt bounce.
OPTIMUM gas drive does not provide for gobs of extra energy to work extra power springs with weak ammo.
The ejection pattern is interesting but also one of the intentional results of our configuration.
OPTIMUM is relatively insensitive to ammo selection.
The ejection angle and cyclic speed with different ammo changes relatively little compared to other configurations like 16" MID or CAR.
This is a good thing, as we'd like any ammo to run nicely and don't always get to choose the loadings ( issued, availablity, stockpile, etc)
Due to proper timing, OPTIMUM is relatively sensitive to changes in reciprocating mass or buffer weight.
This is also a good thing, as we can generally control the buffers and carriers used.
Shorter gas systems show a variable amount of unlocking friction.
With them, lighter buffer unlocks sooner under more friction, so it gets lets impulse to cycle, but needs less due to the lighter weight.
Similarly, a heavier buffer unlocks later under less friction, so it gets more impulse to cycle, but needs more due the higher weight.
This effect is somewhat self defeating when heavier buffers don't slow down the action as much as expected.
With OPTIMUM, the unlocking friction is low and relatively constant, so a lighter buffer cycles faster and a heaver buffer cycles slower, as expected without the variable unlocking friction forces.
The lightweight reciprocating assembly and aggressive brake need a bit smaller port to run best.
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