Copied an old post of mine on this topic from the AR board:

I have had Kodiaks in .58 and .72 -- both a lot of fun, but I miss the .72 the most. I found a couple of round ball targets fired over the Oehler chronograph with the .72. Hate to disappoint, but shooting a patched 540-grain .715 round ball over 120 grains Goex Fg and using an RWS musket cap (I put musket nipples on), I show a high of 1,032, low of 996 for an average of 1,009 fps.

Just found some more chronograph notes in the range notebook. The .72 Kodiak gave 880 fps with 120 grains Goex Fg and 1,050 fps with Goex FFg and musket caps shooting an 840-grain conical -- the classic paradox cotton-spool pill, probably from an NEI mould. I also show an average of 1,246 fps with the 540 grain round ball over 150 grains Goex Fg. I have a target showing the single shot I took with that 840-grain conical over 150 grains Goex Fg, but no chrono reading.
By the way, I see notes on the .58 Kodiak showing a .570 Hornady patched round ball over 120 grains Goex FFg and a Remington cap giving an average of 1,651, with an SD of 26.

Hope this is of interest.
I should also note that Jeffe, who sometimes posts here, has one of my old .58s and has gotten over 1400 with heavier minies and Triple 7, but noted that beyond these performance levels the guns are getting a little beat up.
The .72 is much more stoutly built over the chambers, and has a barrel about three inches shorter than the .58s, making it a real natural choice for conicals.