What diameter to size boolits for Marlin 30-30 with Microgroove rifling?

[got_lead?]

Helllo all:

I have a Marlin 336 with microgroove rifling and am about to try some cast boolits in it. This is my first experience loading bottleneck rifle rounds with cast boolits.

If the barrel slugs at .308, what diameter should I size the boolits?

Also, if I were to use boolits w/o gas checks, are there any guidelines on hardness, powders, or velocities that would help me with working up a load? Do I really need a gas check?

Any help would be greatly appreciated.

Dave

[missionary5155]

Good morning
Start with a SEARCH here in Leverguns. Take the time to read what is already written.
You want to discover your rifles throat diameter - they are not all the same. Throat diameter will be larger than the barrel diameter. Fill the throat and good things happen.
Same with GC boolits.. fill the throat. I would not be surprised if the throat diameter is .310+. .312 is not unheard of. That is one reason the Ranch Dog moulds are made fat.
Micro-groove barrels also benefit from a tight boolit so be loading throat diameter boolits you are supplying the barrel with a good tight fit.
Mike in Peru

[got_lead?]

Mike:

Thanks for the info, I've looked through many of the lever posts looking for info on the 336, I'll try the search.

How do I check the throat diameter? Do I tap the slug in just far enough to engage the rifling, then measure it?

[Maximumbob54]

The Ranch dog sight offers .310 sizing dies and Lee makes a .311 one. I shot some .309 sized and it wasn't lead city in the bore but there was a little. I'm crossing my fingers that the .310 or .311 lubed right will fix it. Oh, and mine was in a 30AW Marlin.

[skeet1]

I use a .311 diameter for my 336.

Ken

[btroj]

I would start at .311. You may not need to ever try anything else.

[izzyjoe]

well if you'r barrel slugs at .308, then i would go .002 over and start from there. but will have to play with you'r lube to see what it likes. i have good luck with the lee 170.

[adrians]

my 30 cals get fed lyman 308291 or 31141 as dropped usually .311 and just love them the 30-30 eats 31141's and my 308,s ,308291 (311291).
i'll have to get a 311290 someday.

[pls1911]

.310 should be plenty.

If your throat can take it try a .312...
Slugs are minimaly sized (if at all)when gas checks are seated and lube is applied, and work well in early square bolt marlin as well as microgroove models.

My slugs are cast soft and heat treated HARD, 25 bhn.

[imashooter2]

My 30AS microgroove slugs at .308 even and I get best results sizing at .311.

[rhouser]

I have a 336 that was the most hateful b*tch you ever put hands on. Would NOT shoot a cb of any type in any way. I checked foreend, I tightened, I loosened, I shaved, I fire lapped, NOTHING Worked. I bought a ranchdog 311-165 CF and ranchdog .310 custom lee bullet lubricater/sizer and first time out nearly dropped my teeth (yeah over 60). Dirty B*tch turned into a princess. First group at 50 yards off a rest with iron sights was under an inch. Shot 5 more 5 shot groups with the same results. Sell my 336, I don't think so. She shoots like a dream. Shoots sub 3" 10 shot groups at 100 with the irons and my old eyes.

Note: These bullets also work in my .308 and 30-06, I just use a standard Lee .309 Lube/Sizer instead of the .310. Some day I may try these in my garand,

Thanks to the guys at Ranch Dog Molds. They have solved all my Marlin issues.

I ave the RD's in .30, .32, .44, .460 to go with my Marlins. I just ordered the .22 for my hornet. What can I say. If it works, keep doing it.

By the way, these bullets flat drop game DRT. Good working meplate.

thanks rc

[GREENCOUNTYPETE]

I'm using as cast .310 from a c309-170rf mold in a micro groove , no leading issues i have tested up to about 1600-1700 fps estimated without gas checks

it was most accurate at 14-1500 fps

my powder is H4895

the lee book has the reduced data for 30-30 that's what i work from

[BAGTIC]

With any gun I always start with as cast just as long as it is small enough to chamber. You can always work your way down later.

[got_lead?]

My boolits are casting out at .312, and they just fit down the necks of my fired brass, so I'm gonna start with a .311 sizer and give er a try.

[phaessler]

I have found reasonable succes at 0.311" in my 30AS.

[Char-Gar]

Marlin MG barrels in 30 cal, tend to run larger in the grooves and lands that other barrels. I not you said.."If the barrel measures .308". Have you measured it or are you just guessing. That is the place to start.

Marlin MG barrels will do very well with cast bullets, but often require a bullet of a different size that other 30 caliber barrels. They can be special needs barrels.

[1Shirt]

Just my opinion, but as big as will chamber in your rifle. Probably .311, but maybe even .312. No wabble down the bbl and leading with oversized!
1Shirt!

[ProudOkie]

So my 183 lead bullet is dropping .3125, not sure why? Too big you think?