Cast 45-70 help

This is kind of long, so thank you in advance for reading it through.

I've been loading the 45-70 for about a year now and am having a ton of fun as well as a ton of frustration. After discovering that Accurate 5744 was my most accurate powder, I continued to tinker with different loads to get it just right. Initially I was testing with Missouri Bullet 405 gr and Starline un-trimmed brass (about 2.105"). I don't recall getting any leading unless I increased the charge over 28 gr using a WLR primer. This was fine because my most accurate load came from 25 gr with the same primer at about 1250 fps.

In an attempt to get a more consistent load, I began trimming my brass to 2.095" to ensure my crimp was the same on every cartridge. I don't know whether it is related, but at about the same time, I began getting leading in the first one or so inches of barrel immediately in front of the chamber. The first time I noticed it was shooting un-crimped loads that I was testing for bullet movement while in the lever actions tube. My initial thought was that not using a crimp was the cause of the leading. I then tried a light crimp, a tight crimp, and even annealing my brass. I've tried both Missouri Bullets and Laser Cast (both 405 gr) with the same results. I get no leading using H4895 (never tested beyond 48 gr), but my loads aren't as accurate as they are with the 5744.

The only possible causes that I am able to come up with are:

The leading was always there after using this bullet powder combo and I never noticed it while cleaning (not likely, as I'm pretty meticulous);

I was clearing the leading with my other test loads of H4895 (I didn't always keep records of which load I shot first);

Somehow, trimming the brass .01" is the cause of the leading;

Missouri Bullet's sent me a batch with a slightly different alloy or lube composition, or diameter (never tested Laser Cast before the leading started), or

I've somehow bulged my barrel immediately in front of the chamber, allowing hot gas to get around the bullet (pretty sure this in not it).

This leading isn't unbearably hard to clean, and I will continue to use this load if I can't find a suitable substitute, but would really like to get this solved.

Any suggestions, or input is greatly appreciated.

They should be the same hardness as before, as the only thing they list for this bullet is 18 BHN. I did try upping to 26 gr, but with CCI 200 primers. The CCI's are a little colder than the WLR's that I normally use, so maybe that countered the powder increase. I'll give 26 a try with WLR. I just thought it was strange that, everything else being the same, I would suddenly start getting leading after I trimmed the brass. It may not have even occurred at the same time, just close enough that I can't say it didn't. Same with the batch of bullets, don't know if I switched to the new batch or not when this started happening. Thanks for the suggestion, I'll give the powder increase a try.

BigBore,
I’ll be sure to check castboolets. H4895 with these bullets never causes leading. It may be due to the higher pressure, though not much higher.

Charlie,
I’ll measure my chamber length and see what I come up with. As I said in my original post, I don’t recall having this issue prior to trimming my brass, so maybe 0.01” makes a bigger difference than I thought it would.

243winxb,
I knew that 5744 is a faster powder than H4895 which is what makes it a good option for magnum handguns. I suspect that the initial spike in pressure is what’s causing the problem. I’ll load up some Trail Boss and see how it does. I believe it’s an even faster powder.

Ireload2,
I’ve got a lee hollow base mould, can’t remember the model number, that casts a .461 bullet. I’ll try some soft alloy and see what happens.

243winxb said:

if bullet diameter is undersize , may work?

I like slower powders. Good luck.View attachment 786863

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I like slow powders too, that was how I ended up with so much H4895 and the fact that it can be loaded very mild for letting the kid shoot big bore stuff.

someguy2800 said:

I love trail boss in 45-70. I shoot 19 grains with a 350 lasercast and a magnum primer.

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Under a 405 gr bullet, the max recommended by hodgdon is 13 gr for about 1005 fps. I think I was getting close to that, and very consistsnt velocities. Makes me chuckle every time I fire a round. Any idea how fast your 350 gr’ers are going.

So, I slugged my barrel and got about .457”-.458” depending on how I held my tongue. My Missouri bullets are .459” and the Laser Casts are .460” so both should be big enough. I was able to track down some bullets from my first order and some untrimmed brass. I made up some loads that are identicle to my first several batches of test loads which I plan to test out tomorrow morning after work. We’ll see how it goes.

I did some testing this morning and here is what I found. I fired two rounds that I assembled from un-trimmed brass, bullets from my first order of Missouri Bullets, and 25 gr. Accurate 5744. These two rounds leaded my barrel in the same place, so I was able to rule out the brass trimming and new bullets as the cause for leading. I then fired two rounds that were loaded with the same components except using H4895. These two rounds removed all of the leading that was deposited by the 5744 loads.
So, what I came up with is; this load always leaded my barrel, but I was just removing it again with 4895 loads. As I said before, I didn't record which load I shot first, only my observed results at the end of the day. If I was removing the lead with my second or third test load, then my observation would have been no leading.
Now to come up with an accurate load using H4895, or maybe I'll try H4198 as I've read good things about it.
Thanks for all the help and suggestions.

I’ll be sure to pick up some 4198. I also like shooting TB, but want a little better trajectory. I hope to use this rifle on elk this year.