It is my understanding that the buffer weight has an effect on the rpm since heavier weights cause the rifle to take longer to cycle. I am getting a SP1 conversion soon and would like to save costs on ammo (really funny that I'm penny pinching after buying a 25k-30k gun) and increase controllability. What are y'all experience with different buffer weights? Is there a major difference between carbine and H4? How about weights that are one step from each other like H1 vs H2? Thanks in advance.

Look at this thread just a few down the page: https://www.ar15.com/forums/Armory/M16-Ultimax-/23-544953/

Bunch of info on my site: https://c3junkie.com/?page_id=164
Kinda scattered though.
This is also relevant with some cylic rate info as well: https://c3junkie.com/?page_id=977

Sweet, thanks!

There are also the two-piece buffers, but I have never tested them as far as cyclic rate goes.
However I do know, they eliminate bolt carrier bounce completely.

Tony

I've ran M16 9mm ROF tests on a number of buffers.  For the type of buffer pictured (two-piece steel 9mm mechanical, 5.6 oz.); using a Colt M16A; Colt 16 in. 9mm ‘pencil’ barrel installed in Gibbz Arms G9 side charge upper receiver; 9mm, ramped, direct blowback bolt carrier group (15.6 oz.); standard, mil spec, six position carbine length buffer tube without spacer; and standard round wire carbine length recoil spring and obtained 869 RPM as an average of five runs (10 rounds per run).

MHO, YMMV, etc.

ETA: And as a couple of points for comparison using the same configuration except for the buffer used -
H3 buffer(5.6 oz.): 971 RPM, and
Steel shell carbine length buffer w/3 tungsten weights (7.5 oz.): 886 RPM.

AETA: [Note that even though the steel shell  with tungsten weights buffer weighs more than the two-piece steel 9mm mechanical buffer, the rate of fire is higher.  Buffer configuration also is part of the ROF achieved].

Assuming one is discussing centerfire calibers, to get the lowest rate of fire, one probably has to use a hydraulic buffer in connection with whatever other elements are implemented in their configuration.