My Marlin 30-30 has a mind of his own

[lonewolf5347]

Well the weather yesterday was perfect so off to the range I went funny things don't seem to work out the way they should.
I shot some Lyman 311041 at .311 and .309 with GC they shot o.k. but not what I was looking for on paper.I loaded them with IMR 3031
24.5 and 25.5 grains. I did notice both loads had a little blow by on the case neck.
I did also try the lyman RN cast bullet again not great.
I slug the bore a few nights ago it went right at .308
Now a good friend had some Lyman 311041 sized at .308 with GC with annealed cases loaded with 2400 powder they shot the best 5 shots at 50 yards maybe a 1' group FPS was a little under 1500 no gas blow by.

[btroj]

Sometimes you have to listen to the gun.

I would increase the 3031 charge and go with .311 bullets.

[lonewolf5347]

My friend said also to increase the powder charge for a tighter seal.

[btroj]

That would reduce the soot on the outside of the case. Those are pretty low pressure loads with 3031.
With that bullet and 3031 you should be able to pretty well duplicate factory ammo speeds.

[BCB]

I use that boolit with an old 336--from the 40's...

I have found better accuracy with IMR-4831--33 grains--and WC-852--35 grains (slow lot)...

Velocity was 1700 and 1711 respectively...

Twenty-four and one-half grains of IMR 30-31 gave me 1656 fps and accuracy was not nearly as good as with the slow burners...

Good-luck...BCB

[GabbyM]

Howdy Lonewolf:

Do you know what the hardness of those 311041 bullets was?
If they are just air cooled wheel weights it's probably simply to soft for a microgroove barrel.
I realize here are people here that jump seemingly impossible hoops with a micro grove barrel and void any claims the MG barrels won't shoot cast. But in the single 336 we have only heat treated hard bullets will shoot very well. I have shot BHN #9 gas checked 150 grain Saeco over 16gr of 2400 but results were nothing to brag on. I have better luck with Rx7 in my Win 94. Never got to try it in the 336 as that rifle is in AZ and I'm in IL. Slower powder does help with a slower acceleration. or so the theory goes. 3031 should work great and if it doesn't I don't think I'd blame the powder. Like btroj says. increase powder charge. May sound counter intuitive but a bullet can grip rifling better when more pressure is behind it to obturate the thing. For reduced velocity loads it's better to go with a faster powder. Lyman list 27.0 grains at 2016 fps and 31,300 C.U.P. As there top end load. But that's well below maximum MAP. About 26.0 grains would get you down into the 1,900 fps range which is probably where you'd find best accuracy.
Between here and there are about a hundred variables with accuracy.