Oops... I did it Again...
 

I can't help myself sometimes. I did just buy one very nice air pistol, my new Weihrauch HW 45, a spring piston gun in 5mm (.20) caliber. I really, really like that pistol.

Well, it appears that way back when, when Weihrauch were commissioned to build these for the old Beeman company, they experimented with a single stroke pneumatic version of it. They never intended to produce the pneumatic version. It turned out, however, that it was just too good not to produce it, so they did.

And, yeah, you guessed it - I just bought one. Darn it. :D It's their HW 75, available only in .177 caliber. On the outside, it is remarkably similar to the HW 45, as one might suspect:

http://forums.pelicanparts.com/uploa...1554567862.jpg

Internally, however, it is a far different pistol. As a single stroke pneumatic, it stores energy in the form of compressed air, rather than a compressed spring. You can see its big air cylinder in place of the not so visible spring hiding deep in the HW 45:

http://forums.pelicanparts.com/uploa...1554567862.jpg

The firing sensation is completely different between the two. Spring piston guns have noticeable "recoil" as the piston is released and the heavy spring drives it to compress air in front of itself. The pneumatic has no "recoil" whatsoever. It is much louder than the springer, has a good deal less power, but has the potential for greater accuracy, since it isn't jumping around before the pellet exits the barrel.

The other cool thing is that the hammer really fires it. On the springer, the "hammer" is really just the catch to hold it shut. Pulling the trigger releases an internal catch on the piston. On the pneumatic, though, the catch is a separate button, and the hammer actually strikes the exhaust valve on the cylinder to release the air. Pretty cool.

The HW 75 might just be accurate enough to use in local air pistol matches. It by no means has the power to be "rat worthy", but that's not why I bought it. What a fun little plinker, though. And, as everything Weihrauch, absolutely top quality.