Gentlemen: I recently acquired a 375 Marlin rifle with the Micro Groove rifling. I have shot some loads in the 2000 fps range with the Hornady 375 220bn bullets with Rel. 7 powder. Accuracy is not very good- 5 inch groups at 50 yds. Mostly vertical stringing. The Barrel will not group at all unless some twenty rounds through the barrel. The barrel copper fouls a lot. Today I went out with a 260 cast bullet load over 32 gns of Rel 7 and got some fair, not really good groups with more horizontal stringing.

Does anyone have any suggestions as to a good load with the above bullets. Are there any "tricks" in tweaking the forend or magazine tube for better accuracy.

Thanks,
Hoot Murray

if you are getting bad horizontal stringing i would look at the rifle not the loads.

Yup, look on leverguns.com and read the article on accurizing the lever action.

I have a 375 Marlin also. Like yours mine fouls quickly. One of those get around to it things I need to do is shoot about 200 round through it with cleaning about every 5 rounds to knock down all the high spots on the lands. The interior of my bore looks like a file on top of the lands.

Also be sure to hold the rifle by the fore end and rest your wrist or hand on the front rest as if you were shooting in the field. A lot of folks try to shoot a light center fire by adjusting the rear bag with one hand and the pulling the trigger with the other. That allows the rifle to jump vertically causing stringing. Hold on to the fore end and some of the stringing will go away.

SR4759,

You have been reading my mail! I have looked down a helleva lot of barrels and I have never seen one that even came close to the 375 Win, Marlin. The lands and grooves both look like files. I have shot 100 rds of the 220 gn Hornadys. Does not look like a lot of smoothing going on. Odly enough, I shot 20 264 gn Lyman Cast Bullets with gas checks, all grooves lubed, except the crimping groove and sized to .377. No leading and these were moderate loads according to Ken Waters in his load book. The groups were about 2 1/2 to 3 inches with a slight amount of horizontal stringing. These are 50 yd groups. I have a Lyman Aperture sight on the rifle.

I always hold on to the forearm when shooting off the bench with rifles with substantial recoil. I did take DWright's advice and looked on LeverGuns.com and found some pretty good articles on accurizing.

I was thinking that first I probably should lap the barrel but after reading some of the articles on LeverGuns.com where the bore size on all Micro Groove Barrels are oversize coming out of the factory. So lapping would only make the situation worse. Think that I will play around with the forearm and magazine attachment to the barrel.

Thanks, to all who answered my post. I really appreciate your help.

Tenga cuidado,
Hoot

I have yet to see a single 375Win that has been fired anywhere near enough to have broken in the barrel
sufficiently to even justify it's owner having BOUGHT bullets moulds to load for it much less shoot cast bullets in it.

Clean it THOROUGHLY and shoot it a bunch more

And you might want to consider a couple of afternoons
spent with a wool mop and a tub of JB bore lapping compound.

the operative phrase here is "Non embedding garnet abrasive"

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