45-70 microgroove & cast bullets


September 21, 2011, 03:47 AM
Out of interest, has anyone cast and sized bullets big enough in a microgroove marlin 45-70- like .460 or above- and not had success with accuracy and lack of bad leading?

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September 21, 2011, 11:36 AM
No personal experience, but I asked the same question a while ago on a different site, and was told that the larger calibers use non-microgroove rifling. I'm sure someone will correct me if I am wrong.

September 21, 2011, 11:39 AM
I did a little research. Appears that the microgrooved barrel was used until the "late 1990's" for the 45-70. Not sure when the 460 was introduced.

September 21, 2011, 11:42 AM
Good info on loading lead bullets in a microgroove:

Marlin's Microgroove Barrels
by Glen E. Fryxell


September 21, 2011, 05:18 PM
yep, the older 45-70s had micro grooves, along with the 444s etc.. Some people say they shoot cast fine, some say there are problems. A lot say you need a larger bullet - like .460 at least. But I haven't been able to work out if sizing them big is a garanteed fix all the time. I'm thinking of getting one and the microgrooves go for a lot less but is it worth it?

September 21, 2011, 10:33 PM
Use a gas check bullet and cast 'em hard or paper patch 'em. Slug the bore and size appropriately (.002" over bore size). Shoot, enjoy.

A few million microgroove rimfires have put a gazillion rounds down range with few problems.

September 22, 2011, 12:51 PM
Had one, late 70s - early 80s. Shot well with jacketed bullets, not so good with cast, and I tried a number of molds, loads, etc. Even tried wrapping cast bullets with Teflon pipe tape to make them hold the rifling. That one also liked to let cases pop past the cartridge stops, so they would wedge under the shell lifter. You had to unstick it by prying on the primer with a small screwdriver........Not a big fan of doing this. The newer rifles have Ballard style rifling for a reason, and that reason is the popularity of cast bullet shooting. I would most surely spend the extra for the Ballard rifling.

Jim Watson
September 22, 2011, 01:00 PM
When the new Marlin 1895 came out in the 1970s it was listed with "conventional rifling for lead and jacketed bullets." They also explicity authorized handloads "as recommended for the 1886 Winchester." A friend had one, the barrel was 8 groove rifled and shot all bullets well.
Soon after, they changed the spec to "Modified Microgroove suitable for lead and jacketed bullets." But then before long they went to regular Microgroove and quit talking about handloads.

Current guns have conventional 6 groove rifling. I don't think a 21st century Marlin employee would recognize a Ballard rifling pattern if it bit him on the knee. But it is good advertising and Marlin can use it with some legitmacy, they once owned Ballard.

September 22, 2011, 01:03 PM
I read often that micro-grove rifling doesn't like cast bullets and newer Marlins don't have it for that reason. All good info already posted herein. However, micro-groove rifling makes an accurate rifle using jacketed bullets and always has.

September 22, 2011, 04:25 PM
Watergoat - what did you size the bullets at? Did you slug the bore?

I'm just wondering whether you can always make a microgroove shoot cast well so long as your size large enough. So far I haven't heard anyone say they sized 460 or over and didn't get a MG shooting good groups...

September 22, 2011, 04:46 PM
I had a marlin with microgroove rifling. It didn't like plain base lead bullets at all but would shoot close to MOA with gas checked.

Red Cent
September 22, 2011, 07:47 PM
Micro groove = jacketed or plated bullets. Gas checks would work. Lead will shoot but accuracy will go downhill at every shot. Lead buildup.

September 22, 2011, 10:36 PM
I shoot a .462" 440 grain pure-lead flatnose out of my early-70s microgroove 1895SS using Pyrodex with light compression (1/16"-1/8"). Lube is Lee Liquid Alox rumbled around in an old peanut butter jar. I usually run a .410 bore shotgun bore snake through a couple times, then clean like regular. No leading problems so far, and I get around 1350 fps. Nice, mild load that would still do the trick on most any animal, I'm sure. :)

Maybe the peanut butter helps? Dunno.

September 23, 2011, 01:41 AM
Sounds good, how's the accuracy?

September 23, 2011, 07:16 AM
the only "glitch" i have in shooting cast bullets from my microgroove 30-30 is i have to run bullets that are .002-.003" larger that the bore diameter. if i shoot smaller, i get quite a bit of leading. the best spot on the web for cast bullet information is http://castboolits.gunloads.com/forumdisplay.php?f=8. literally thousands of posts only concerning cast bullets, problems, and advice. i have been a member for several years there. if there is one word that is THE key for shooting cast bullets, it is FIT. everything else is secondary.

Red Cent
September 23, 2011, 10:44 AM
The oversize bullet is somewhat providing the same effect as the gas check. It is sealing the heel of the bullet and stopping the hot gas.

My Marlin in 38-55 has a standard bore. Should be .376. Slugs at 379. Very little leading. Its used in cowboy side matches with 240 gr at about 1100-1200. Very little leading. Slow bullet.

September 23, 2011, 09:06 PM
Sounds good, how's the accuracy?

I can usually cover a 100 yard 5-shot group with my hand. Call it 2-4" on average. That's with iron sights off the bench. Occasionally, I'll get a group where they all touch. I'd like to get a receiver peep for this gun, but until then, I'll struggle along with the buckhorns ;).

The oversize bullet is somewhat providing the same effect as the gas check. It is sealing the heel of the bullet and stopping the hot gas.

Agreed. Having a bullet that's four thousandths over nominal bore diameter is a great help. I'd like to try alloying these bullets and pushing them even faster with smokeless powders.

Also, my mold is a "one-off" from Lee that I got in a group buy a few years ago. It's got tumble-lube grooves and a gas check, and pure lead bullets weigh in at 440 grains with no check. It's supposed to be 425 grains, but I think that's with Lee's #2 alloy.

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