If you're using a rifle tube, then it needs a rifle buffer. If it has a pistol or carbine tube it needs a carbine buffer. Don't mix those together; one way (rifle buffer in carbine tube) won't cycle at all, and the other way (carbine buffer in rifle tube) will damage parts when the carrier slams into the receiver. Barrel length doesn't really matter to buffer and tube size (you don't have to use a rifle tube with a rifle barrel, carbine tube/buffer is fine too), that choice is mostly about what stock you want to use and which tube it fits.
Keep the springs matched up correctly as well, they are different.
Other than that, you can play with different weight buffers to figure out how your rifle shoots the best. That is one method of balancing the operating system, while adjusting the gas flow is the other common method.
Good post..
