I have loaded 4198 powder 37.5 grains,in 45-70 with a 300 grain Nosler partion bullet. After usual cleaning with a patch,
I dip a bronze brush in Butches Bore shine ,same for patches.
After a few strokes with the brush,I follow with another patch.
This patch comes out grey and stiff
I continue with more patches till they seem clean, then another good brushing . The following patch coues out just as grey and just as stiff.
I repeat the entire process and result is the same.
I have had the same experience in a 375 H&H Magnum with the beartooth 255 grain lead bullet with a Gas Check on top of 40 grains of 4198.

[U]What is the grey substance I get with both leadgc and jacketed bullets?

Swifty,
I think what you are seeing is simply carbon fouling. With relatively low pressure loads it is common to get quite a bit of powder fouling. I don't believe you are getting the barrel thoroughly clean using your method.

I generally find it takes a much more liberal application of solvent than you are using to get a barrel really clean. Brushing can loosen gunk up, but the solvent is what really "washes" the bore. Give it a try and see what you come up with!

In addition to what IDShooter pointed out, you will get some kind of discolored patch out of the barrel every time you put a metal (not plastic) brush through the bore before the patch. Even with a perfectly clean barrel you will get crud from the brush wear.

It sounds like you are getting carbon fouling or brush crud, but if the entire wet area of the patch is grey I'd go with powder fouling.

Hick is right - I actually revisited this thread to point out exactly what he said; you will always get discoloration after brushing, especially with a solvent on the brush. The solvent works at the metal in the brush as well as the jacket fouling!

After one good brushing, I would finish with alternating wet/dry patches until clean. Rarely should you need to brush again with today's effective solvents.

That's a pretty light load for the .375H&H and a light but reasonable (Trapdoor) load in the 45/70. Each powder has a pressure range it works best at, and these are on the botton rung of that ladder. At this level, combustion is just not going to be as complete as it would with higher pressure loads....not just unburned grains, but the secondary products of combustion are likely to be left as fouling.

In other words, light loads with most smokless powders are more dirty.

Can be cleaning as well. Watched a friend of mine cleaning a new rifle...kept cussing becasue no matter what he did, the patches came out showing a trace of copper fouling. He'd been cleaning a good while, had a nice sized pile of used patches at his feet.

Noticed the patches were dirtier on the INSIDE of the patch than on the part rubbing the barrel....super good coper solvent and a BRASS brush.

I'm old school when it comes to cleaning, I always soak the bore with a patch, let it stand on a newspaper for about an hour (bore down) rewet, then brush. Run a few patches down the bore dry, rewet and let stand another hour, scrub with the brush, run two dry patches down it, rewet with solvent, then dry patches until dry. Oil it and store. For copper fouling I wet the bore and let it stand for several hours, rewet repeat until, the stain on the newsprint is black not green, or very little green, I like shooting so I try not to go overboard, unless accuracy drops. Take care and have fun. Swany

Find the easiest way (for me) is to get the bore wet with solvent at the range while it's still hot. Know it will proably dry in the case as it's transported back home, but it seems to make cleaning (at home) easy. Not something to do with a harsh chemical cleaner like Sweets.

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Was shooting a Rolling Block 45/70 with the staring load listed under the "trapdoor" section (300gr. cast and 32gr. of 4198). Was woking well, accuracy wasn't great, but was acceptable. One round went "pthisss". Opening the breech, the primer was hit and an empty case came out...but just ahead of the chamber was a solid mass of powder.

Had to dig it out..was scorched..kind of melted together into a blob, with some of the dark color missing and some parts looking a bit transparent. Bullet was in the rifling, with the powder mass jammed against it's base. Dug out powder, drove bullet back out (was nicely rifled...made a good barrel measure), and STOPPED SHOOTING THAT LOAD! All remaining of theat load were dissassembled.

Now...to your poblem...was a nice layer of caked-on crud in that breech end, from case rim to where the bullet base stopped (about 1" into the rifling). Looked like melted plastic..acted like melted plastic...but eventually solvent removed it.