6.8 spc upper

[thumper]

This has probably been addressed before but i can't find any posts..If i switch to a 6.8 upper for my M-4 will i need to replace/strengthen the buffer spring? Or could i just use the same one as the 5.56?

[Olaf]

You can use the same buffer and action spring.

[fdxpilot]

My 6.8SPC rifles have all had either a Daniels or BCM lower from G & R Tactical, equipped with a carbine spring and H buffer.

[kac]

Presumably, the heavier bolt/carrier group soaks up much of the additional impulse.

[caporider]

Presumably, the heavier bolt/carrier group soaks up much of the additional impulse.

6.8 uses 5.56 carriers - no difference whatsoever.

The 6.8 bolt is probably fractionally lighter than the 5.56 bolt due to the wider bolt face (and smaller lugs).

[kac]

I stand corrected, and thank you. Wonder why a heavier buffer, then, wouldn't make a little sense.

[Clint]

Guys,

The buffer and spring have almost nothing to do with the actual recoil generated by the cartridge.

Recoil is taken up by the bolt lugs and barrel extension.

The buffer weight and spring have everything to do with the gas impulse produced by the powder and gas system length.

Any upper in any caliber can be just right, over gassed or under gassed.

Odds are the 6.8 upper will cycle the same as the 556 upper you took off.

[thumper]

Thank you gentlemen..One more problem solved..