Still need to have sights and a new stock put on the Marlin Tomcat, but here is what the case looks like compared to the original .25-35.

Bill,
I have had my best luck with IMR 4320 in my Marlin 25/35 Imp. I'll be curious to see what you come up with.

Ive had such good luck with H-380 in my standard 25-35s that I would probably just have to try it in the IMP version..If I ever come across a cheap Marlin that's pretty rough, I will build myself a Tomcat..The main reason I have not had one is my 250-3000.

Ray, H-380 is right up with CFE223 on the Hodgdon data site for velocity with the Hornady 117 RN.

Interesting project. I would love to see pictures when it nears completion. I've never actually seen a Tomcat before.

I have one of Francis Sell's books and really enjoy it. But I guess living in the foothills of the Cascade's that's only natural.

yep I was going going to rechamber one of my 25-35 Winchesters I had five but solod them all.The 25-35 Ackley improved is 600 pfs faster than the regular one in a 24 inch barrel .

In my guns I maxed out at 300 FPS over factory loads???and that's just real good..Would you be so kind as to give us your loads, I would surly like to try them in my gun, and chronograph them, that's awesome..

Fellas, it will be a while before I have the rifle completed. I just sent some nice walnut to George at Treebone Carving for him to turn me his semi-crescent early Ballard style butt stock.
http://www.treebonecarving.com...levergun-stocks.html
I plan to have Jerry Huddleston engrave the receiver with "Sell, Donnelly, Ackley .25-35 Tomcat," and then it will be off to Wyoming Armory for the lever and receiver to be color case-hardened.
She'll be a looker when finished.

What kind of pressures do those hot loads produce? I assume they are safe enough for a lever gun. My first centerfire rifle was a Winchester 1894 25-35.

FLA: The idea of expanding the case capacity is to permit more bullet speed at similar pressures to the parent cartridge.

I have an ancient Handloader magazine in my outhouse with a write up on the Tomcat. I also have a fellow trapper in a village 20 miles away with a 25-35 that is getting older and starting to sell a gun or 2 on occasion. Maybe it's time to start working on a Tomcat project?

I had a chance to put a strain gauge on my Marlin 25/35 Imp before I blued it.
You will find a slight sticky-ness in the lever before you hit unsafe pressures if it's anything like my rifle.

Rat, John Taylor Machine in Puyallup, Wa., has my reamer.
Back40, that's good to know. Thanks.