I have been playing with mine trying to find a factory load that works well. I used the Winchester white box to hunt with this year. Accuracy from it was pretty good ( 240gr). The 300gr do not shoot well at all in it. Hornady 300gr is what I tried, had heard the twist is wrong for that load and it is--mine was shooting 5-6in groups at only 25 yrds. My favorite so far is the Magtech 200gr recoil is very pleasant. I was looking for a lighter recoil load for this gun--I bought it for a youth gun and something my wife would hunt with anyway. I shot a 6 shot group that measure 1 and a 1/4. I had two bullets slightly to the right which where my fault or this group most likely would have been MOA. The 240 grs I have tried are stout, the 200's are a pleasure to shoot, and oddly the 300's are too. I ran the numbers through a recoil calculator and the 200's and 300's where between 8-9 ft/lbs and the 240's where about 13-14 ft/lbs. I ordered some bulk 240 grs that have been on back order since December but will save my brass and work up a load for the 200 gr's. I did buy some of the PMC 240 gr that shot all over the place, but other than those and the 300gr everything has shot better than I thought it should from a lever gun. As for the max length, go to the Marlin website and download the manual, it list them there--all the factor stuff is fine though at least what I have tried--I Jammed the gun the first time a cranked the lever and it was due to the plate where you load the mag caught the bullet--it was hard to get it apart but was an easy fix just tighten up the screw that holds it. Has not jammed since.
