I have 2 Chucksters, 1 is the mannlicher stocked 640M and other is a plain/homely 640KA. I cut the KA barrel back to 19" to improve the balance and make it handier. They are reasonably accurate even with the crappy triggers, about the same as the same vintage Savage 63s and 65s. The scope mounting groove on the receiver are spaced such that you may find it necessary to modify the rings or bases to fit properly.
Unless the rifle is priced right and you like it, I think that almost any Marlin in the 700, 800, 900, and XT series made within that last 30 years is likely to be more accurate and easier to properly mount a scope on. Many .22 Magnum fan think that the tubular magazine Marlins in the 783, 883, and 983 series are among the best all-around .22 Magnum bolt guns yet to be made.
