Marlin Bore Diameter

[Bzcraig]

I have read numerous posts stating that Marlin 336 w/mirogroove rifling typically need a larger boolit. I finally got around to slugging the new to me 336 I got recently. When I put the mic to the slug I got .3084. Has anyone else gotten similar results? Should I still order a .311 sizer?

[Keyston44]

I size mine to .310. I couldn't close my lever with them sized to .311.

Key

[w30wcf]

My 336A slugs .308" and I have used .309., .310 & .311 diameter cast bullets and they all performed pretty much the same.
The old tale of a microgroove needed a larger than normal bullet is pretty much false....same as microgroove won't shoot cast bullets.....

I have checked several different .30-30 Marlins and .3085" is the largest I have seen.

w30wcf

[Dean2]

Interesting to read that some of you are getting micro-grooves to shoot cast bullets well. I had always heard the old saw about them not shooting cast well, and having no experience or people I knew well who had experienced different, just took it at face value. Going to have to take one of my micros and try some cast through it. Thanks for the info.

[myg30]

.002 over grove is fine as long as you work up your load with the boolits you cast and if you change the lead recipe then you might want to work up the load again. I shoot 50/50 ww/pb gas check tumble lube and have run .004 over. there was no difference so .002 is fine and no leading. I seat the boolit just touching the lands with slight marks on the boolit but not to tight to have trouble ejecting or loading it.
Marlins are great rifles and you will enjoy lots of shooting with it.

Mike

[JFE]

Before ordering you might want to try to get hold of some larger diameter bullets and check to see what is the largest diameter that your rifle will chamber.

My Win 94 or Savage combo wouldn't chamber a cartridge loaded with a 311 bullet.

[pls1911]

I run all my heat treated .30 boolits through a .312 die which rarely touches the sides except on the SAECO 160 grain. Allshoot fine in micro groove barrels

[6pt-sika]

I used to cast for and reload for a dozen different Marlin 30-30's . Originally I used .309 later I changed to .310 and eventually I went to .312 and it worked in all the rifles I had also accuracy seemed better to me .

[blixen]

For what it's worth, I've been shooting 185gr. .311 boolits in my 336 with good accuracy. .314 won't chamber.

[TXGunNut]

.311's chamber fine in my latest 336, no prob in earlier one either.

[jh45gun]

For what it is worth on the Microgroove think about this if the microgroove did not shoot lead well then their 22's would not be worth a damn and those of use that own them know how well they all shoot.

[blikseme300]

My 1965 Marlin 30-30 shoots well using .310 sized cast. Micro groove works with no leading. It is pure FUD that MG does not work. My other MG Marlin's work well with CB's also.