AR buffer

[bodiebill]

How do you determine the correct buffer?

[bohoki]

if the one you start with causes problems go up one till it works?

its best to test the upper on a lower with a rifle buffer first

[ar15barrels]

How do you determine the correct buffer?

It depends on the length of the buffer tube, the gas system length, the gas port size, the barrel length and the type of ammo.
Lacking an adjustable gas system, you use buffer weight to "tune" how the gun cycles.
In general, you will want to run the heaviest buffer that the gun will cycle with, unless you have an adjustable gas block.
With an adjustable gas block, you can run the lightest possible buffer and tune the gas system.

The heavier weight buffer will tame the way the action cycles when the gas system is not adjustable.
A lighter weight buffer with a adjustable gas system will reduce how much the gun jumps around on each shot.