Now I've got over 10 years of experience taking apart and rebuilding various models of guns such as 1911's, M1 Garands & M1 Carbines. But I'm just starting to mess with the AR15 platforms in the last year.

Now I initially purchased two a DPMS in the style of the M16A1 with the lighter barrel, no shell deflector, , triangular hand-guards, fixed stock, early style carry handle and sights.
And a Bushmaster in the style of the M16A2 with the still attached carry handle with the newer style iron sights that are easier to adjust, rounded hand-guards, fixed stock, heavy barrel.

Now as anyone who has fired an AR15 or M16 will know that you can hear and in some cases even feel the buffer and spring recoiling back and forth in the tube in the stock as you're shooting it.

Now for some reason the DPMS is very loud and clanky to the shooters ear, and yet when I fire my Bushmaster it's a whole another world it's much smoother and quieter.

At first I was thinking that the Bushmaster had a much heavier buffer in it. But I removed the buffers from both rifles and weighed them using a digital postal scale. Placing them each in the center of the pad standing up on the flat forward area that engages the bolt carrier.

The results were that the DPMS weighed in at 5.1oz. while the Bushmasters buffer weighed in at 5.15oz. Now I really doubt that .05oz. would make that much of a difference in the feel of the action during recoil not to mention the noise.

Again I'm New to AR15 so I could use a little guidance here from some of the veteran armorers out there.

Why is the Bushmaster so much quieter and smoother in the stock tube while shooting vs. the DPMS and what would you suggest I can do to make the DPMS function in the same/similar manner to the bushmaster?