Man, I've seen this topic somewhere before.......LOL
I shoot both the .22 Mag and the .17HMR, and based on what I've seen with the .17HMR in comparison to the .22Mag, it creates a hell of a lot bigger impact reaction on my plate steel targets at 100yds.
Where you'll get a decent lead splash with the .22 Mag, the .17HMR round actually crater's the steel...try it.
Not doubting Remington's figures that Don mentioned, the results I've seen with it are far more convincing that it really performs quite well, but for different reasons.
The .22 Mag might show higher energy figures at 100yds. (I don't have that data in front of me), but velocity has a greater role, in corellation with the much lighter, smaller diameter bullet, to produce more explosive performance.
I've mentioned this before, but it's the old "slow & heavy" in comparison to the "light & fast" theories.
The light and fast round, depending on the situation, will surpass the slow and heavy loads only out to a given point. Trajectory is better, but the lighter/faster bullet, once it reaches that given point will shed it's velocity faster due to it's lack of mass.
Different weight bullets in the same cartridge perform the same way, but, with the necked down diameter of the .17HMR, and the large reduction in bullet weight, we're talking about a major variation between the two.
The end result is that the .17HMR has much more explosive performance only out to a given point. Beyond that the .22 Mag takes over and carries it's energy farther downrange. The other factor is the trajectory variation between the two, which the .17HMR has the edge.
Considering that they're both shortrange guns, this can be argued pro or con.
I like them both, honestly, but I can "visually" see a gainful advantage with the .17 if kept within it's realistic "useful range". Beyond that range, the .22 Mag might have a gainful edge on energy, but at the range where that occurs, the level is so low that it's almost a moot point.
I think alot of the same arguement can be carried over the the .22LR and .17M2 debate as well.
Either way, a lot of companies nowadays, in trying to strive to develop newer and better cartridges to enhance sales, really seem to be splitting hairs, and reinventing the wheel somewhat.
Just my 2.........
Take care,
Bob