I have a Sig Mosquito, a Browning URX 7.5" barrel, and now a new Alpha Project .22LR revolver. The revolver will be fired for the first time next week when I go to the range. I have found indeed, the Mosquito needs the Blazer mini-mags (either, oh 36-grain or 40-grain, I think - both work). It jams, as indicated, with the other ammo I have tried. I have to tell you, though, the URX is the cat's meow. well-built, all metal construction, excellent sights, and the thing is a tack-driver. I really, really enjoy shooting it. The Mosquito is less accurate at 25 yards (of course, it's barrel is about 3" shorter). I find I'm using the Browning most often.
As an aside, cleaning the Mosquito is a PITA because I have the model with the "compensator" on the front, which needs to be removed with an allen wrench.
My two cents.
Cannon