Buffers & Springs

[lysander]

A regular M4A1 shooting M855A1 ammunition in a time-displacement study was found to take about 0.006 seconds to drop from a velocity of 3 to 3.66 m/s to zero on closing.

A standard bolt carrier has a mass of 0.4366 kg.

Throwing all that together, the average force during locking is 266 Newtons, or 59.8 lbs.

[prepare]

A regular M4A1 shooting M855A1 ammunition in a time-displacement study was found to take about 0.006 seconds to drop from a velocity of 3 to 3.66 m/s to zero on closing.

A standard bolt carrier has a mass of 0.4366 kg.

Throwing all that together, the average force during locking is 266 Newtons, or 59.8 lbs.

I imagine an AR9 would be even more?

[lysander]

I think we've talked about this before but the bias spring in the VLTOR buffer is very soft. I don't think the weights stay at the front (muzzle-end) of the buffer under acceleration from the action spring.

Weak springs indeed, less than 0.90 lbs at rest for the heaviest weight set, less than half a pound for the lightest weight set. For reference, a ball-point pen spring produces about 1.8 to 2.0 pounds of force.

[zeus100]

update on min buffer weight performance..
FYI my adams arms piston BCG weighs 9.37oz or 0.265kg, signifigantly less than the .4336kg noted by @lysander above....(fyi my carbine DI BCGs range from:
non-FA carrier 11.25oz;0.3189kg 5.56 bolt to
FA carrier 11.56oz;0.3277kg 7.63x39 bolt ) So wondering what kind of M4 BCG is weighing 0.4336kg??

i ratcheted the Strike Industry Optimus buffer weight down . "same" results mean that cases continued to be ejected at the 430-5 o'clock
2.1oz, then 1.28oz,
brass M193 62g same; cycled, 4 o'clock; cycled
brass 223 REM 55g same; cycled, same; cycled,
steel 223 REM 55g same; not cycled, same; cycled,

so I did get the Steel Tula ammo to cycle without getting to absolute empty buffer (0.99oz) or further opening the gas port.
however no real significant movement in the angle of case ejecta

[Clint]

update on min buffer weight performance..
FYI my adams arms piston BCG weighs 9.37oz or 0.265kg, signifigantly less than the .4336kg noted by @lysander above....(fyi my carbine DI BCGs range from:
non-FA carrier 11.25oz;0.3189kg 5.56 bolt to
FA carrier 11.56oz;0.3277kg 7.63x39 bolt ) So wondering what kind of M4 BCG is weighing 0.4336kg??

That is the entire reciprocating mass, including the buffer.