For your info: a magazin of a Buckmark will fit the Challenger, is not nice, but it works. But not the other way around: no way a Challenger's magazin will fit a Buckmark.
BTW: what does it mean "II"? I know the Challenger model (with different barrellenghts) and I know the Nomad, which is a cheaper made Challenger, but I'm not familiar with the mark "II"
I will have to try the Buckmark mag, but I don't think it will work. My daughter has a Challenger II, and I have one defunct worn-out mag and one good one for it. I've been having trouble finding mags for 4 years now. The earlier model challenger mags are different and won't work. This is why I doubt the Buckmark will work (since it works for your, earlier, Challenger).
EXTREMELY accurate, at least in Tessa's hands. Hers has been set up with a heavy spring, and it just loves CCI Mini-Mag ammo. Cycles VERY quickly. Still have a couple boxes of that left, then it's driving and searching again. DAMN Massachusetts - NO shipping ammo to MA.