The A5 buffers are lighter than the regular. H2 is heavierr than A5-2... A5-4 is going to be really heavy. Not sure I have heard of anyone going that heavy.
Somewhere I have read about switching the inserts to make a weight you want but I have never seen the thread, directions, video, or whatever the post was referencing. I -thin- maybe some people get the heavy one and reduce it down by altering the internals... but not sure how it's done.
A5H2 = 4.5 oz
H2 = 4.6 oz and 3.5 reciprocating weight. Not sure how the latter weight is in the A5.
A5-H4 = 6.5 oz
Holy cow.... This site says if suppressed use their 10oz buffer!!
http://www.heavybuffers.com/vltor.html they do sell a buffer kit and inserts though to tune your buffer.