This past Friday (8-6) I got to the firing range with my chronograph and worked with my handloads. While I was at it I shot some Olin/Winchester M855 and some Ingman "Hot Shot" SS109 62gr. Green Tip. Here's my results (I'm including the Olin/Winchester M855 as something to which to compare the Ingman SS109).
Ingman SS109 "Hot Shot" 62gr.
Average velocity: 3,059.05 FPS
Hi: 3,091.64 FPS
Lo: 3,007.14 FPS
Extreme spread: 84.50 FPS
Standard Deviation: 27.80
Olin/Winchester M855
Average velocity: 3,091.42 FPS
Hi: 3,123.55 FPS
Lo: 3,051.11 FPS
Extreme spread: 72.44 FPS
Standard Deviation: 24.91
The above data results from one ten shot string of each ammo type. While I was at it, I also shot ten additional rounds of each for accuracy. This was a rather informal test, but this is what I did. Two three shot groups and one four shot group at 100 yards. The Ingman gave me an average group size for the three groups of: 1.5" and the Olin/Winchester gave me an average group size for its three groups of: 1 5/16".
The gun used was a Bushmaster A3 w/20" chrome lined, 1:9 twist. The optical unit was a Burris 1.5x6 x 40 scope which is mounted on an A.R.M.S.#5 multi base with Leupold medium rings.
The Chronograph used was a Gamma Master Chrony. Readings were taken 15 feet from the muzzle.
The conditions were: approx. 72 degrees, sunny, dry, very little wind.
I only shot a total of twenty rounds of each ammo, but there were no malfunctions nor problems of any kind. Based upon the above results I would conclude that the two ammo types are very closely equivalent. Certainly the Ingman does not seem to be related to the NATO stuff that has been loaded down in order to work in the SA-80 Bullpup.