Matt, no way will it go anywhere near supersonic if you keep the same reg pressure, more like 900-950 fps.
Personally, I think the arrival of the 16 grain JSB and all it's clones (AA/Daystate/Ripp) has blown away the argument for .20 at FAC levels.
It used to be that a 14.3 grain .20 premier with a BC of 0.032 represented the best balance of trajectory and downrange energy. However, with the JSB having the same BC, and with the extra efficiency of .22 over .20 making up for the 30 fps that the JSB would otherwise be down by, they have the same trajectory, but the .22 has a tad more power and makes a bigger hole.
Also, of course, you have far more alternative pellet choices.
at 12 FP, .20 gives you another 5 yards (all things being equal) over .22.
In addition to my own BC testing, have a looksee here....
http://www.straightshooters.com/ourtake/sup12grid.html
NB the Daystate figure of 0.028 is rather low - 0.032 is more usual
HTH - JB
PS AXL, why .177 FAC ? Would be 24 FP, approx 1000 fps with 10.5 grain stuff (BisMags or CPHs) .177 is a very small hole with nil expansion, doesn't increase your range as much as a .22 FAC would IMHO (i.e. killzone remains small as damage is limited)
Last edited by Shed tuner; 10-01-2005 at 04:25 PM.
Reason: .177 FAC footnote
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.