I found a ton of info on carbine buffers, but not much on rifle.  Can buy std/H/H2/H3 and know what weight you get (and can mix/match weights).  If you need to adjust your buffer with a rifle system, there is not much information.

ETA I believe this is an AR10 rifle buffer, slightly shorter than an AR15 rifle buffer (see below) rifle buffer (mine) has 4 steel weights, one spacer (feels like aluminum), 5 rubber pads.  (rubber weight rubber weight rubber weight rubber weight rubber spacer)

If you take it apart you can change the weights by adding Tungsten weights (from taking apart H2 or H3's in my case).  
Weights are 0.540" (tung) to 0.5435" (steel) diameter and 0.613" tall.  You can buy tungsten online, pinewood derby sites sell them (not sure if diameter is exact, one site I saw said 3/8" which would be 0.375, so that would be too small...

The spacer is nearly exactly the height of 2 weights with one rubber spacer (1.2985" spacer, 1.294" 2 steels and a rubber).  You could take out the spacer and put in 2 more weights and a rubber between them.  I suppose you could put in 2 spacers and only use two weights also.  There are basically 6 "slots" and the spacer takes 2.

Housing, roll pin and bumper 1.454 oz
Steel 0.64 oz
Tungsten 1.45 oz
Spacer 0.33 oz
Rubber pads 0.012 oz

Lightest to heaviest:

1.45 oz. : empty housing with bumper and roll pin
2.47 oz. : 3 spacers with 3 rubber
3.44 oz. : 2 steel, 2 spacers, 4 rubber
4.24 oz. : 1 steel, 1 tungsten, 2 spacers, 4 rubber
4.41 oz. : 4 steel, 1 spacer, 5 rubber (STOCK)
5.05 oz. : 2 tungsten, 2 spacers, 4 rubber
5.21 oz. : 3 steel, 1 tungsten, 1 spacer, 5 rubber
5.38 oz. : 6 steel, 6 rubber
6.02 oz. : 2 steel, 2 tungsten, 1 spacer, 5 rubber
6.82 oz. : 1 steel, 3 tungsten, 1 spacer, 5 rubber
7.62 oz. : 4 tungsten, 1 spacer, 5 rubber
8.59 oz. : 2 steel, 4 tungsten, 6 rubber
9.40 oz. : 1 steel, 5 tungsten, 6 rubber
10.20 oz. : 6 tungsten, 6 rubber


EDIT: my buffer was out of a LaRue OBR (the early ones had rifle buffers, they now use carbine I think).  I found the picture below that shows A1/As rifle buffers have 5 weights and a spacer:


I did check to make there weren't any weights left in there (couldn't shake it out if it was).
Weights are all calculated.  Using a digital RCBS reloading scale and a complete buffer was too heavy to register (so POSSIBLE I had a 5th steel weight stuck in there).  If so correct me and I can re-run the numbers with the additional combinations.

Topic Moved

Looks like AR10 rifle buffers were 5.2" and 5 7/8" for M16 rifle (and AR15's).  So that would fit a 5th wt.  Gives more options, I think I have them all (?)  7 slots, spacers count for 2 slots

True AR15 Rifle should be:

3.12 oz 1 steel, 3 spacers
3.93 oz 1 tung, 3 spacers
4.09 oz. 3 steel, 2 spacers
4.89 oz. 2 steel, 1 tung, 2 spacers
5.06 oz. 5 steel, 1 spacer
5.70 oz. 1 steel, 2 tungsten, 2 spacers
5.87 oz. 4 steel, 1 tungsten, 1 spacer
6.03 oz. 7 steel
6.51 oz. 3 tung, 2 spacers
6.83 oz. 6 steel, 1 tung
7.47 oz. 2 steel, 3 tung, 1 spacer
7.64 oz. 5 steel, 2 tung
8.28 oz. 1 steel, 4 tung, 1 spacer
8.44 oz. 4 steel, 3 tung
9.08 oz. 5 tung, 1 spacer
9.25 oz. 3 steel, 4 tung
10.05 oz. 2 steel, 5 tung
10.85 oz. 1 steel, 6 tung
11.66 oz. 7 tung