ARs typically have a loud sproing when shooting.
Is yours louder then other ARs?
From what your describing it sounds like normal AR action on a carbine length (14.5-16) rifle with normal buffer...
If you do want to smooth it out and go with a H2 buffer,I know the Spikes one has gotten good reviews.
BTW: I did a quick search on heavy buffers at arfcom and got a dozen results including one specifically about changing out the buffers in Bushmaster M4gerys