I don't have a compact, but have a Katran L in .177, and it is one of those guns you don't ever want to get rid of. Yeah, they're that good! As to velocity, mine came from the factory shooting 10.5gr at 915fps avg, and a 9fps ES for the entire string. Holy cow it's consistent. I was extremely happy with it as is, so I've not monkeyed with it.
Now, if you shorten the barrel, I would expect that the max velocity, (which I would imagine, I'm, at least, close to on mine), would be somewhat less, maybe in the 50-75fps range.
As to accuracy, well, no worries there for me. All of the rifles I keep are accurate, and can be counted on for that accuracy any time I pick them up. The Katran rates at the top of heap for sure. As I said, it's one of those rifles you won't want to let go of.
I actually lucked into mine, when I was simply looking for "something new" and had money burning a hole in my pocket. After perusing the online ads, and having been scammed, I decided to only buy from reputable forums or businesses online. So I looked at Utah Air's website and saw a used Katran. I called and found out the this one had been taken from new stock, used at a local shoot to advertise the brand, and returned to stock for sale as used. Wow! did I hit the jackpot, a stellar rifle and great price. UA is at the top of my list for many reasons, but also for turning me on to the Airmaks rifles. I had zero previous knowledge of the brand and took the advice of the salesman, and he was being modest about these guns.