I can share my experience on the .22 Short.
Loudness:
I reduced the power on mine to 20 fpe. At this power it is very quiet and needs no additional moderator for backyard use. At the 32fpe that it came to me shooting, it would need an additional moderator for my backyard.
"Jumpy:"
Prior to purchasing, I had read the the Short was a little more difficult to hold steady. I'm approaching this response with that impression of what you mean when you say jumpy. I haven't shot a Standard or a Long but was pleasantly surprised with how easy it is to shoot. Now, that's pretty subjective so I'll share a somewhat less opinionated example of a comparison between the Short and a full-length rifle. At the most recent Field Target match I shot through the formal competition with my Mac1 Hunter. It is a very long gun with knee riser and thigh supports, basically a purpose built gun for Field Target. I shot a 35/40. I shot through again about 2hrs later with my ,22 Taipan Veteran, set to 20 fpe. Both guns have a 20x SWFA and I ranged by focus both times through the course. So, a fairly scientific comparison with the major difference being that it was a little more windy with the Veteran. Anyway, I shot a 33/40 the second time through. A couple of caveats: I am more familiar with how the Mac1 performs in the wind than I am with the Veteran. The most surprising to me, and the most helpful to you in your jumpiness question, i went 4/4 on the offhand shots with the Veteran and only 2/4 on those same offhand shots with the Mac1. The Veteran was markedly easier to shoot offhand than the long=gun.
So, it is anecdotal, and really only an n of 1 test, but, the Veteran performed much better than I thought it would, in comparison to the purpose-built Mac1 gun.
I just see that you responded while I was typing that and that you are referring to the pulse (cant really use the word recoil with a PCP) of the gun firing when you say jumpy. WIth a scope, even the Short is probably topping out around 9ish pounds. At my reduced power level I don't have much of a pulse when I shoot it.
I know the reduced power thing isnt what most people go for around here but, as an aside, I am getting around 100 consistent shots without a shift in the pellet impact at 55 yards. That shot count, and the reduced noise, are pretty appealing to me. Further, if I cranked up the power, I would want more sound moderation, which would make the gun longer, and one of the whole reasons I purchased it was for the convenience of a nice, short little compact package.
There's gotta be more than .02 in all that.
