Lee Loader

So when im bored at work, or showering, or stuck in traffic, or just about any time ive got a few moments alone with my thoughts im usually thinking about reloading anf shooting. Lately ive been on this idea to have, eventually, a Marlin 336 in .30-30 and a Ruger Mini-14 'Tactical' in .300BLK both sharing the same cast bullet (a 150-170gr) as a cheap plink bullet for the majority of my loads

Then i learned that most Marlin 336s' bore measure at slightly larger (is this the microgroove rifling?) at closer to .311. This comes at quite a disappointment. Does this mean ill never be able to share a (cast) bullet between these two cartridges despite both being nominally .308 caliber?

There's two general 336 .30-30 chambers. Not sure if the barrel is different. RD made two different molds.

I think.

I use the RD design made by Lee for my '51 Marlin waffle top, my Yugo AK variant, and my yet to be shot one year old .300BLK AR home build. I do size the .30-30 and 300BLK down a very slight bit but run the bullet as dropped in the AK because it has the loosest barrel (by history).

You are making a mistake considering only bore diameter. To me, the major consideration of a cast bullet is matching the nose profile, ogive, to throat taper and then worrying about the groove diameter. I think if all you consider is groove diameter, then you have a 70% chance of failure.

How do you figure the match out? A chamber cast and measuring tools. No other way to do it, other than trial and error, which leads to the large rate of failures.

The problem with JB Marlins is not their oversized groove diameters but their oversized throats. JB used over diameter throats to facilitate cartridge feed, and this is why Remington (and Rossi) has had such a hard time with a CAD drawn and produced rifle. Precision part match allowed lit slop so the rifle could not chamber a cartridge within the confines of the precision tolerances.

There is a world of differences between the 30-30 Win (in general) and the 7.62x39; nothing is similar; so no, you will not find success with a common bullet. The 300 BO might work with a 30-30 Win bullet, but in general, I find it a poor cast bullet cartridge as it was designed with a lot of freebore and throat for a very heavy jacketed bullet pushed subsonically. Most casters only would read "heavy" in my last statement and think "good to go." The trouble with the space that was designed for a heavy jacketed bullet is that with the cast it becomes a "black hole". You can add its short case neck as a negative as well.

Oops, thanks for the response GG. Some important clarifications, i started reloading over a year ago but cant now due to my tools and gear being in a storage unit 2000mi away but when i was reloading i used only powder coated cast bullets that i purchased online usually from Missouri Bullet Co or ACME. I would like to get into casting my own but its something that will have to wait, amd considering i just got back onto the Navy who knows when ill feel settled enough to start

Back to the question, its half hypothetical since i dont own either of those guns, and half frustration at seeing a plan fall apart. I know the obvious answer is 'load jacketed, dumdumb' which i suppose could be where i leave it, buying cheap PC cast lead for my pistol rounds (my fantasy/plan includes .38SPL, .380, .45ACP, & .45lc) and 150-170gr .308 jacketed from the rifles which begs the question are jacketed or plated bullets for new 336s also oversize at .311?

Yeah I made a mistake with my early morning post. My Lee RD mold is for .30-30 only. It's a tumble lube GC 6-hole for my gun.

I use a single (other) mold for both 300BLK and 7.62X39. It's a Lee GC lube groove off the shelf mold.

Sorry...

Most of My 30-30's and Both .300BO's like .311...

Fit is King...

I have a little trouble with that much reach . I have a couple of moulds that work fine across several cases . I load the x39 , 30-30 , 308 , and 06' . The 06' is happiest with the 312-155 which the 30-30 likes also but the 30-30 actually doesn't seem to care what I feed it as any of 7-8 moulds work one about as well as another . The 308 has a very narrow window and seems to like long bearing lengths . Paper patched works best as it also prefers fast loads and won't shoot anything over 175 gr even if it were a WC . The x39 has a barrel .305×3165 my best success with naked cast was a 323-170 sized .323 with a .318 dia nose which feeds and chambers fine . I paper patched a .309 sized 200 gr spire point finished at .318 . (.318 is the original groove dia of the 8mm Mauser) . Don't know where I got off into the x39 ......

.308 grooves seem to be pretty standard .
Microgroove barrels need to have bullets on the fat side .
I would recommend a NOE 311-165 RD or a similar Lee . If the 30-30 is in a bolt gun then the 312-155 is an option .

How much do you think you'll shoot? I've spent a fortune saving money casting "free" lead bullets.

If you enjoy it as a hobby that's a different story, but if you think you'll be able to buy one mold and then use free lead to feed both guns you will likely be disappointed.