hey jaymo... yes, it is the qb57. You do not need a new spring. I lube tuned mine and shot it... a lot. it's got like 2 tins thru it and it gained a bit of FPS to settle in the high 600s and low 700s (it shot 723 with hobbies and for giggles, 804 with pba!). I found a consistent pellet (the daisy wadcutter 7.8 gr) that is also decent in accuracy. It has done great and is a great squirrel hunter. head shots up to 30 yards are certain and quick death. I love anything that is a take down or a bullpup, so i looked at the baikal 514, but found it to claim very low speeds. have you shot one? what do you think? starlings? squirrels? range? I even wanted a izh 61 but ended up getting a Daisy powerline 953. witha little 4x32 is deadly up to 20 yards. is small, quiet, and looks offly tactical. i also got the mother of all tactical rifles, the Talon SS... but that is a whole different ball game...
But you are right, the 57 or 67 is a great little gun, and really under estimated. great urban hunter, fits in a back pack, pack a decent punch (it will shoot as hard as a HW30 or R7...) and is available in both calibers, plus you can buy a .177 and later on buy just the barrel assembly in .22 from archer airguns.