If you don't plan to shoot cast bullets, any rifling type will do. Some people say the Micro-groove doesn't work well with cast. Unless you're prepared to spend a 50% premium for a longer barrel, 20" is the standard. According to many people, quality went down when Remington took over Marlin, so JM stamped Marlins (pre-Remington) bring a premium. Same with pre-safety. While I have no newer "Remlins", I think it varies rifle to rifle. If the price is too steep, well ya gotta pay if you wanna play. You can shop around, and deals are out there occasionally, but you might not be huntin' with one this fall.
