I chronographed (Oehler 33) several .22 magnum rounds from my Hi-Standard D-101 derringer the other day. The two rounds I was interested in were the "short barrel" designed Gold Dot 40 grain load and the Hornady 45 grain FTX rounds. Thought you might find the results interesting as the barrel length is similar to the model 351.
Here are the results of the forty round test. Temperature was around 75 degrees, all ammo staying in the shade:
Winchester Super-X 40 grain ammo - 10 rounds (stuff is around forty years old):
LO: 1024
HI: 1225
ES: 201
AVG: 1099
SD: 63
Gold dot 40 grain ammo (20 rounds total fired in two 10 round strings):
LO: 960
HI: 1243
ES: 283
AVG: 1132
SD: 88
LO: 1066
HI: 1278
ES: 212
AVG: 1148
SD: 64
Hornady FTX 45 grain round, 10 rounds fired:
LO: 946
HI: 1190
ES: 244
AVG: 1070
SD: 74
A couple of things. I'm dubious about those "HI" readings of +1,200 fps, especially that 1,278 fps Gold Dot reading. I had several readings of well over 2,000 fps, clearly from burned and unburned powder messing with the chronograph. Those were erased and are not in the calculation.
So, even just looking at the lowest velocities recorded, it seems to me that all rounds were very similar in velocity output. Thus, I have to ask myself, what's the advantage of these new .22 magnum rounds, which were designed for use in short barrel handguns?
If anyone else has tested these rounds I'd be interested in seeing their results.
This is the pistol used. Grips removed to enhance concelability:
______