I've been exactly in your shoes.
I had good luck using a .311 bullet from MBC in 150gr, using H4895.
I wish I had gas-checked bullets back then to puch 'em harder, but they were all sorts of minute-of-deer, and very pleasant to shoot.
Don't reinvent the wheel, lots of good info here :
http://www.thehighroad.org/showthread.php?t=585381&highlight=marlin
in short :
150 gr sierra FN
31.0 gr h4895
COAL 2.540
165gr LFN
20.5 gr h4895
COAL 2.510
I don't use 170 jacketed in mine....couldn't get 'em to group no way.........
I stopped the experimenting with the above recipes when I got them to within 2" @ 75 yards standing ( with irons ) for the jacketed, and 3" for the LFN's. you will enjoy the economy of LFN's if 3" is good enough for you.
http://www.leverguns.com/articles/fr...ve-barrels.htm
"The key to success with cast bullets in a Marlin with Microgroove rifling is to keep in mind that these barrels tend to have oversized groove diameters, and that the grooves/lands are shallow. Therefore, in order to get proper engraving (and minimize "slippage" of the cast bullet as it enters the shallow rifling), it is necessary that the bullet completely fill up the groove diameter of the barrel, and engage the maximum amount of the driving surface of the lands. Since Microgroove barrels are commonly oversized, this means that the cast bullet must also be oversized to effectively "fill up" the grooves. "
" Because of the specifications adopted by Marlin, Microgroove barrels tend to have oversized groove diameters, and as a result, Microgroove barrels early on earned a reputation for not shooting cast bullets well. In fact, when loaded with bullets that are the appropriate size for the barrel (and cast to a suitable hardness and wearing a GC), these guns are capable of fine accuracy with cast bullets."
As an example, in my .30-30- using unchecked LFN's from MBC, I have them sized to .311.
My initial results using .309 were a failure, .310 were better, but not anything I'd even remotely call a "group"
I finally got a decent barrel slugging, and found my diameter to be .3095 at its tightest about 2 inches from the start of the rifling.
With that knowledge in hand, and help from members here, I was able to obtain .311 LFN's....that is the day I started seeing something that resembled groups, utilizing a scope from the bench.
Once I had an appropriate load dialed in, I removed the scope, and began to shoot Standing unsupported...eventually reaching into the 3" range using the entire magazine.
I have a Marlin U/L in 30-30 Win & wish to make up rounds using a 150-160 grain Lead bullet. I do not wish to push it too hard as I prefer not to use a gas check.
