Leading at the throat and Unburned powder in the bore ?

[hylander]

Marlin 336 38-55
Iron sights, 50yds.

Just got back from the range.
Got just a bit of leading at the throat, no where else and there is unburned powder kernels in the bore.
Total of 32 rounds fired, 27 rounds with WW 2.082 and 5 rounds with Starline 2.125 brass
All fed and functioned great.

230gr. sized .379 flat base non G/C
21-23 gr. IMR 4198
WLR primers

21gr., 1.80" with the Starline brass, the WW brass loads had flyers.
22gr. 2.4" with WW brass
23gr. .96 with WW brass, which was the last group fired.

Ideas on the light leading ?
I'm thinking it is not lube, as the leading is at the throat only.
Do I worry about it.

[uscra112]

Bullet might be undersized for the throat. The throat dictates bullet diameter, not the grooves. But that load of 4198 seems mighty light to me. The pressure you're getting isn't enough to make 4198 burn completely, and probably the rise time is too slow to upset the bullet into the grooves properly.

If you want the 1400 fps M.V. you're getting, something faster would be in order. I happen to be a big fan of Blue Dot for such loads, but the Schuetzen guys, were they to use the .38-55, would be using AA#9 or AA4100 (Ramshot Enforcer is the same powder). Somewhere about 12-14 grains will be right for any of those. Don't worry about precision; it would take 5 or 6 grains more of Blue Dot before you get to the SAAMI limit for the .38-55, which is 35,000.

4198 would be the canonical powder for G.C. wheelweights at 1850 fps. for hunting. You'd be up around 30 grains with that weight bullet.

[rmcc]

As for unburned powder, had same problem. Read an old , I believe Bob Milek, and he said increase crimp a little at a time until unburned either went away or case was deformed. At that point it was time to change powders.

[hylander]

Well, I just loaded up a few rounds of the .381 Hunters Supply bullets from Midway.
They are a no go.
They will not chamber with the WW 2.082 or the Starline 2.125 brass.
The Starline brass comes closer but will not chamber.
So wondering if it is worth ordering some .380, I just hate to order a bunch of bullets
just find out they may not chamber either.

[uscra112]

OK, try a faster powder first, then. Sounds like your bullet size is OK.

Increasing crimp does have an effect on peak pressure and will shorten the rise time, but you're so far from what 4198 likes that I'm skeptical that it'll do enough good. Nonetheless it's cheap and easy to try out. Another way to shorten the rise time would be to seat the bullets out until they are in firm contact with the rifling in the throat. Make dummy to do trials. Drill the primer pocket out of a case with a #7 drill, and tap 1/4-20, so you can use a long bolt to push the bullet forward until you get what you want. I do this for almost every development, and when I've got it right I run the bolt in, Loctite it, and cut it off so my dummy is now a tool for setting the seating die forevermore. But I'm a single shot guy; I never have to think about whether the OAL will interfere with cycling through the action or fit a magazine! You may not be so lucky, so the heavier crimp may be your only option. (Me, again because I'm shooting single shots, I never crimp at all.)

'Course, I should ask this question: Is there a reason you are shooting at circa 1400 fps? If you are buying your bullets, how hard are they? Probably hard enough that 1600 fps is not unreasonable, in which case just up your charge to maybe 25 grains.

[Cosmic_Charlie]

I just fired some lyman 311041 over 25.5 gr. 3031 and had unburned powder in the bore. About 1650 fps. I will bump it up a half grain and check my crimp.