Ive been shooting lead bullets and casting for 40 years and im stumped on this one. The newer marlin cowboy 45-70 shoots best with rcbs gas checked bullets sized to .459, bhn 25 aprox measured with lbt tester. I use lbt soft blue lube, 29.5 grains of 5744 for 1550 ft per second. this is the best load i can find , but every load i use leads. this load will shoot well out to 300 yards at a 12 inch gong and factory open sights, with bench rest,, Tuesday i hit a 12 inch gong first try at 250 yards with crossticks after 3 previous shots at some rocks on a hillside.... for It depends where the muzzel lead deposits are,if they SEEM to be even it will still shoot well after 5 rounds, but if it tends to lead in an uneven / wrong way it must be cleaned or can spread out groups pretty fast. I have a marlin 45 long colt cowboy that will shoot pure lead bullets 50 rounds with no leading, and it was easy to find that load..

the problems seem to be maybe rough barrel for muzzel leading, and the forard crimp groove and lever feeding mechanism requires too much jump causing breach leading..

there is factory damage to the muzzel about 1 1/2 inches from the front end being tiny divots in a perfect ring looking like a tool got loose or some such, but the leading can somethimes start before that so im baffleled.. I have a lapped c sharps 45 70 heavy 30 inch barrel that has never leaded with ANY load ive put in it..
Leading after 15 rounds causing accuracy problems would be acceptable but after 3-5 rounds has gotten me pretty tired out trying quite a few things to stop leading.. 12 grains of unique gave me no reliefe earlier with softer bullets before i started heat treating wheel weights..
Lets make this an advanced discussion, i order pistol bullets from missouri 1500 at a time, have a dillon 650, and have been reloading for about 50 years.. lead bullets for 40 aprox as i have mentioned..

the only options i can come up with is a new barrel, or move the barrel back to decrease the jump to stop breach leading and cut the barrel off to 24 inches to stop muzzel leading.. It doesn not seem to lead before 24 inches, and is much worse of the barrel heats up at all....

either im missing something, or everyone puts up with 45 70 1500fps leading in thier 26 inch marlin, or this gun just wont shoot lead.. thanks for any input dave.

Tonight i lapped the bore with 250 strokes of 1500 polish compound and 150 strokes of 3000 polish compound just to see what it will do in this situation...
Do you guys have what you call acceptable leading in 45-70 lever gun at 1500 fps? how many rounds do you get before its a problem?, thanks dave.

Im totally changeing it up also, buying 10 rounds from a respectable reloader who isnt getting ledding in his rifles, and going to try 25 grains 5744, 500 grain bullet, single loaded up against the rifleling, 12 bhn for hopefully
ill be able to tell if it the barrel or me with this birrage of tests.. any replys welcome.. dave

Howdy
I've been casting, loading, and shooting 45-70 in a bolt action and a Winchester for a lot of years.
I size my bullets, all gas checked, .459, like you. I use LBT's hard lube. I drop my bullets into water at casting, using an alloy of wheel weights and tin. I have no idea what the hardness is.
Where we differ I use medium burn rate powders. IMR 3031, IMR 4064 and IMR 4895, usually a case full.
With both of my rifles I can seat the bullet out so that I can see rifling engraved marks in the bullet nose.
I'd hate to see you have to scap the barrel.

Jim

thanks for your input.. I had some success tonght (in a spring blizzard, helena montana) but i was anxious to try some different stuff.. what worked is what you guys preach.. I was getting my mold too hot and not watching bullet size for starters so my fit was hurting.. I had a small bag of overweight bullets so i miked them and used the ones minimum of .459 and sized .459. , so i put them under a mild load of 26 grains 5744, and shot 6 rounds in 2-3 minutes with no percievable leading and a warm barrel, so i know im on the right track, the car buffer polish did seem to help alot... The lapping also took care of the breach leading in a medium load of 27 grains 5744 and wheel weights air cooled, , but the bullets were not as large as the overweight ones i shot first.... I cant get my bullets to touch the rifeling becouse they wont feed thru the lever action.....I can single load them tho.... I can start from there, soften the bullets up, get them larger by letting the mold cool, check for minimum diameter and try different loads.. Sure! slower powder makes sence.. Ill keep track of the ones you use and see if i can get some accuracy out of one of these new loads.. Im not worried about velocity, but the gun seems to like big loads.. With a jacketed 400 grain speer it was shooting fantastic and i cant remember how much 3031 but it was 1750 fps or more and i was wearing two past pads and a carhart to keep my shoulder from comming off in the 7 1/2 pound gun, that is where the accuracy was tho for that load., about a 1/2 inch at 50 yards three rounds.. I didnt bother making any more, we dont have any water buffalo around here.. thanks again.. dave.

Make your bullets softer, not harder. They will obturate and prevent gas cutting. I have found that works best at black powder velocities. I use only SPG lube for black and smokeless. No leading. I have been shooting lead since 1968. That means nothing, I know.

I had good luck finding loads with some mixed hardness and powder charges sunday.. One load was 11 bln and 28.2 grains 5744.. It did not lead the first shot,lightly leaded the second shot going into the right spot, and the third round went over the slight leading giving a liberal amount of lube over it, and all going into a 7/16 inch group at 50 yards.. So with your help, and the search engine going to old posts i seem to be making serious headway..The car paint polish lapping the bore with very tight patch also stopped breach leading completely, and made a big difference in all my loads.. The breach leading was what put me into the hard bullets in the first place.. Now soft bullets no longer breach foul.. Im also considering trying 500 grain bullets slowing down velocities, rcbs looks like it makes a 500 grain gas check lever gun bullet, has anyone tried it? dave

The 11 bhn 28.2 gr 5744 and 400 grain gc rcbs cast bullet load, shot well tuesday, with some light leading, but not enough evidently to do serious harm.. It shot 2 groups just under 2 inches mixed in other single shots (chrono etc) in about 10 rounds total.. So thats not so bad with a warm barrel, in fact pretty good for open factory sights.. I looked at another 1895 marlin today that also had leading, that the owner didnt even notice. the 26 inch barrel boosts velocity, and takes alot of lube with a non lapped bore, i got what i paid for, at 700 dollars.. A lapped sharps is over 2000.00. Also i figgured out that the marlin barrel is much lighter and heats up quickly compared to a 11 lb sharps, so im pretty happy with the latest loads im trying... I dont have to clean after every 3- 5 rounds anymore.. dave

I noticed something tonight that goes along with what Jim was saying.. Looking down the bore for the 500th time I noticed that the burnt
powder kernals stopped right where the leading started.. Wow! You would think that once the bullet was obturated it would be fine, but evidently not. as the powder stops the pressure, the leading (probably blowby) is starting.. So i may need to start using slower burning powders like Jim suggested.. I steered away from them becouse the gun likes hot loads, but ill definitly be giving them a try now, trying to find a slow burning powder that doesnt kick like a mule.. ... dave

try .460 dia, things will improve.

4 F
If you put enough IMR 3031 behing a RCBS 400 grain bullet you'll up the velocity another 100 to 300 feet per second, border line uncomfortable.
When I started loading for my Siamese Mauser, Ken Waters had a 3 part article on loading for the 45-70. Some of his loads would really get your attention, especially if you were shooting prone or off the bench.
If memory serves the IMR 3031 load was some where around 55 grains. I currently 45 to 47 grains of IMR 4895 behind a 350 grain GC'd bullet for plinking. I can remember being impressed with how close to the top of the case the powder came.
My play load was a 255 grain plain base using 13 grains of Unique. The bullet mold is one of Lymans 1960-70s no quality control molds and it sized out at .458 or 9. I always put a two inch square of Kleenex tamped down on the powder to hold the powder in place against the primer. The Kleenex most always burned up in the barrel. Not sure if the burning paper in the barrel contributed to the clean shooting and accuracy.
Back then I used what ever bullet lube I could find, but used Mirror Lube mostly. I think this lube was Johnson past wax warmed up a bit to cook off some of the petrolium distilates, making it more firm.
The solution is there on your loading bench and when you find it you'll go "Darn it, I thought about that a while back and didn't do it."

Jim