M16 buffers

[skeety]

Will a heavier buffer slow the cyclic rate? Can I go too heavy? Will I damage anything?

[ExecDirector]

In general, a heavier buffer will reduce the cyclic rate. From DPMS: "The heavyweight buffer is used to slow down the cycle rate on carbine style AR rifles which helps lengthen receiver life. A heavyweight buffer could potentially increase performance with hotter loads or shorter barreled systems by slowing the cyclic rate enough to allow the magazine to ready a new round for the chamber, helping to cure a short stroking problem." There are also hybrids such as the MGI buffer that reduces cyclic and perceived recoil. Here's a review:
http://militarygear.com/asp/2011/07/06/mgi-rate-reducing-buffer-a-review/