I have shot a dozen or better different commercial cast bullets in the Marlin 41 mag with a micro-groove barrel and I have been able to get about any nose design to go into the chamber, but many will not feed properly from the magazine tube. Semi-wad cutters, even with a short, small nose, are "catchy" at best. Without any gunsmithing though, I will say that any TC, Secant, or Tang. Og. will cycle just fine as long as the OAL isn't much over sami specs. LFN or LWN LBT or similar designs are too long and catch. The problem is that I just can't get a cast bullet to shoot worth a darn. The twist is 1 in 20" if I remember right, and even with a gas check, 250 grain bullets shoot mediocre at best. I have shot many whistle pigs and a couple rabbits with 210-215 grain cast bullets, but always within 25 yards or so. At 100 yards, with a Weaver K-2.5 scope and a good sandbag rest, I can't keep a bullet to stay on target; it's more of a pattern than a group. On the same token, with my Contender, S&W and Ruger, I have found a fairly definitive bullet weight for what will and won't shoot. I can get up to a 220 to shoot at about any velocity very well with a variety of powders. A 230 will shoot well if pushed 1,000+ fps, and anything heavier is just dissapointing at any velocity. Smith uses a 1-18.5" twist, Ruger a 19" and the Contender a 20" so that explains it. The only company that puts out a faster twist for shooting heavy bullets in the 41 is Freedom Arms with a 1 in 14" twist. So for anyone wanting to shoot bullets up to and including 300s, that's the route we'll have to go when ever we hit the lottery and can afford to buy one. Another way to go is Shilen sells a .411 barrel that a competent smith could install on a revolver. With jacketed bullets, from Sierra's 170 JHC, to Hornady's 210 XTP, to Speer's old 220 semi jacketed soft point, they all stay inside a couple inches at 100; 85 yards with open sights. The only thing I haven't tried, and I'm embarrassed to say, is my Mtn. Molds 230 TC GC mold. Just haven't had a lot of time to set up and put in a proper casting session. I'm hoping cast hard and pushed fast they'll get me close to a couple inches at 100. As it is, I had to resort to using my 210 XTP load with 22.2 grains of Lil' Gun at 1,845 fps out of the 20" bbl to kill my deer this year. It was a forked horn that I stocked withing 75 yrds or so and was given a pretty ideal broadside shot. To be fair though, the XTP performed suprisingly well going through the shoulder, the lungs, and breaking through the ribs just behind the shoulder on the opposite side; he only ran about 40 yards or so down hill. Will let you know about the 230 TC GC if you want.