Help with A5 buffer choice

[Gödel]

Realistically, the ideal spring is one that closes whatever mass bolt at an appropriate velocity for feeding. That's really its only job. The velocity the bolt opens with is controlled by gas and mass. Stoner designed a BCG, spring, gas tube and buffer that works for a 20" barrel and fixed stock. Colt created the short buffer tube and carbine gas system as a crude adaptation of the full size gun. It is not engineered to the same standard.

If Stoner had been tasked to create a 5.56mm carbine with a 14.5" barrel, it would likely have featured a much longer travel cam way for later bolt unlock, which would have resulted in 20" barrel cyclic rates. But shortening the gas tube and lightening the buffer is never going to result in a weapon that functions as well as the full size - no matter how much you screw around with the gas hole diameter.

[Clint]

Opening velocities are always higher than closing velocities.

Springs have friction losses, so some of the energy is lost.

The buffer impact does return quite a bit of energy.

You can see from this graph, the rebound velocity is about 58% of impact velocity.

Unless you combine overgassing with a stronger spring, there is no reason the bolt closing speeds are going to be anywhere as high as the opening. The opening velocity is absorbed by the impact of the buffer on the back of the buffer tube. So there isn't a good reason for a standard spring to close the action much faster than a correctly gassed action.

[Gödel]

Opening velocities are always higher than closing velocities.

Springs have friction losses, so some of the energy is lost.

The buffer impact does return quite a bit of energy.

You can see from this graph, the rebound velocity is about 58% of impact velocity.

And I think it would be much more lopsided with an overgassed gun.

[GH41]

Interesting, I drilled a tungsten weight just last week.....cutting fluid, patience and a cobalt bit.
Easy peasy.

Whoose bit did you use? What fluid? What RPM? Maybe my lathe isn't stiff enough.

[Mercs]

Whoose bit did you use? What fluid? What RPM? Maybe my lathe isn't stiff enough.

I think CO2 laser should do the job


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[hk_shootr]

Whoose bit did you use? What fluid? What RPM? Maybe my lathe isn't stiff enough.

Dormer center bit, Viper venom cutting fluid, 550 rpm on a drill press. It did dull the bit to an extent.
The tungsten weights were from KAK

[99HMC4]

Carbide cuts tungsten like butter. I do it all the time, just have to have the right tooling.

[hk_shootr]

Correct......didn’t have the size I needed to drill the spring pocket

[Mercs]

Today I received the VLTOR A5 kit and added to the BCM receiver extension for a total of $90 shipped. When cycling the action with the charging handle I can definitely feel a difference, it’s very smooth! Will hopefully get to shoot it in a week or so. I have steel weights from my H buffer that I can use to lighten the A5H2 buffer if needed. Do you guys think I should shoot it first with A5H2 or lighten it up before the first go-round?


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[Wake27]

Today I received the VLTOR A5 kit and added to the BCM receiver extension for a total of $90 shipped. When cycling the action with the charging handle I can definitely feel a difference, it’s very smooth! Will hopefully get to shoot it in a week or so. I have steel weights from my H buffer that I can use to lighten the A5H2 buffer if needed. Do you guys think I should shoot it first with A5H2 or lighten it up before the first go-round?


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I'd do the A5-2 first.