Sorry, Peter, but I've got to disagree with you on this one. The AA PCP's have plenty of power to utilize the full length of a 24" barrel, so there's no way the carbine is going to produce the same velocity as the rifle. This has to be another of the PA typo's, their web site is riddled with them. And oddly enough, it doesn't look like they've ever actually tested a 4XX, none of the velocity figures have that little gray box that gives a pellet weight tested pop up. Not sure which is right, but I suspect the 920 is a factory velocity for the rifle. Based on my experience with my .177 400, it's understated, actual velocity is probably going to be higher with the right pellet. I'd say if you like a carbine, go for it. You're probably only going to be giving up just a few fpe, and at the power level of these guns, that really isn't going to matter. Later.
Dave