For those of you who read the chronicals or the condensed 2 volume set as I had, you will recall the air gun they had, had a roundish reservoir under the lock IRRC and was .30 cal. One of the chiefs wounded a squaw with it - thought that was funny - but it did strike fear into most of them - the rapid fire with no noise, no smoke.

Don't know about the .50 cal for power, but someone with one of the compressed air guns in .45 cal, shot a buffalo with it. 2 shots when only one was actually needed, it turned out. Full length penetration reproted - 450 or 500gr. bullet - low velocity, something like 600fps? Reported to kick like a.416 - something. Saw the pictures nd report somewhere - year or two ago - maybe 3?