Trying to find accuracy in a 45-70 405 Gr Bullet with 4198 powder.

Les in Wyoming

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Oct 10, 2020
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Glenrock, Wyoming
I am shooting a Marlin 1895 CB and have procured a bunch of cast 405 gr bullets. I am limited to 4198 powder as I have invested myself in 8 + lbs of it.

This gun shoots 300 grain bullets accurately with 40 grains of IMR 4198. I have the Lyman book, but it is limited in loads. I have shot 37, 38 and 40 grains under a 405 cast bullet. They shoot all over the place like they were shot from a sling. 40 grains gives a hard wallop with the 405 grain bullet. I don't know that I want to go higher. I will if it would increase accuracy, however.

Is seating depth as critical in this round with a heavy crimp? Should I chase the lands of the rifling and ignore the cantilure? Or should I just load it to the recommended OAL? I could really use some helpful input. Thanks
 

WildBillG

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Sep 5, 2018
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Alberta
I have only shot the 325 FTX Hornadys. But according to the Hornady manual the length of a loaded round is important. I would seat to the canelure and not seat out farther. I used 4198 as well and it worked great. My advice would be to do .5 grain increases in your powder charges. The case does not hold a lot of powder and you may have missed your best load. I hope this helps.
 

Welderboy250

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Apr 19, 2013
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The pressure capacity of the bullet is easily exceeded if the material is too soft. I have no personal experience but remember reading about this in the Lee book.
 

Les in Wyoming

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Glenrock, Wyoming
I appreciate the input. I will try the primers. With this 4198 powder, I just went out and shot 35 grains, 36 grains, 39 grains and 41 grains (having already tested 37,38 and 40 grains). I am shooting open sights at 60 yards. Some of these were impossibly inaccurate. I had 2 - 16" targets side by side and only 1 out of 3 hit the paper! On others, they might hit 2 on paper 14" apart and the other missing. I did get a 3" vertically slanted group with 35 grains. This is beyond crazy. The gun does shoot a fair 2" group with the 300 grain Sieras and 40 grains of the 4198.

I am seating them at the spec in the Lyman book - 2.550". Lyman has max load at 40.5 grains. I have seen others use more under a 405 grain bullet. (This is a Marlin 1895 CB). I am thinking of trying a bit hotter. I just don't know which way to go. I am limited to 405 grain bullets and 4198 powder.

I also just cleaned the rifle thoroughly also. If there are any other suggestions or shots in the dark, please let me know. I just don't see how these bullets can shoot so wild at 60 yards off a rest.
 

chutinlead

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Jan 2, 2020
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Wyoming
Unless you have to have them going that fast, you might try trapdoor loads. Maybe even subsonic. There is another lyman manual for just cast Boolits that might offer more info
 

osprey176

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Feb 3, 2011
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I have not loaded for the 45/70,but have several years of experience with the 444. I found that,at least in my rifle,loads near maximum with IMR 4198 gave the best accuracy. If you are shooting a Marlin,or other modern lever gun,higher pressure can be used. The manual should show different pressure levels ,if not,pick up a Lyman book. The hotter loads do come with more recoil,so a pad swap might be in order,or at least use a slip on pad to test the hotter loads.I haven’t seen good accuracy with reduced loads in the 444 or 375 Win until the velocities were lowered beyond what I consider acceptable for hunting,and I needed to use other powders. Swapping primers will most likely,not give a big change in accuracy,at least in my experience.
 

RT2506

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Jan 10, 2008
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2,139
It is probably not your powder load it is your bullet. Sounds like your bullet is not sized correctly for your bore. They can be too small or too big. I suggest that you slug your bore and see what diameter you get. Size your bullet that same diameter or 1 thousands inch over. The lead mix can also alter your diameter. Some mixes shrink when cooling more than others.

Also pay attention to how much your bullet actually weighs. Different mixes will weigh different.
In my Lyman 405 gr mold wheel weight metal by it self drops a slug 418 grs and a perfect .458 diameter.

I have not found a deer that will stop one using black powder as fuel for 1400 fps out of my Sharps copy rifle out to 300 yards no matter what direction it goes in. I full length penetrated one from chest through butt at 111 yards.

I can attest that with the 405 gr cast bullet 1400 fps is PLENTY of velocity to shoot through anything short of a Abrams tank at 100 yards. My Lyman manual list 35 grs of IMR 4198 as the accuracy load which does a little over 1400 fps.

Also be advised that this bullet will kill game but not like jacketed HP or SP bullets. They kill by putting a caliber size or smaller hole through stuff that is needed to live. Game usually run off if CNS is not hit and often there is not a good blood trail because the hide stretches' then snaps back and almost seals the holes. If fat is involved like on a bear it can plug the hole. Just some of my experience with cast and the 45-70.
 

Varmint Hunter

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Dec 26, 2001
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Long Island, New York
FWIW - my 1895 SBL shoots almost any jacketed bullet into <1.5"moa and some bullets shoot < 1"moa. But for whatever reason, my rifle just won't group well with lead bullets. It will shoot good enough for hunting but the jacketed bullets shoot much better and more consistently.
 

Les in Wyoming

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Oct 10, 2020
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98
Location
Glenrock, Wyoming
OK, latest update (head scratching). I loaded up several charges and shot them at 60 yards. I tried 34 grains IMR 4198 (going down) it shot horrible. Maybe a 10" group. Then I tried hotter loads going half-grain from 41.5 up to 43. The 3-shot groups were so incredibly sprayed, you would think it impossible. I could be more accurate with a sling shot. Some were 18" groups. (BTW, I gave the rifle a good thorough cleaning prior to this). These are cast 405 grain bullets I bought at the store.

So, I also had some other bullets I was able to buy recently. They are also 405 grain. Same shape. They are polymer coated measuring .457. I dumped 40 grains of 4198 under them. The results are in the attached pic. I am greatly relieved it isn't the rifle. I need to bring the sight over a bit, but at least they are together. Two in one hole and one next to it. So you guys were right that it is the bullets. Had these polymer bullets not shot well, I would have considered this rifle to be a wall hanger. But those bullets were the same shape and same weight. So how do you know you are getting good bullets when you find some?

We are going to try to shoot those other bullets in my son's gun to see if they shoot better in his. Assuming they don't (likely) is there anything I can do to make them shoot better? They do not have a place for a gas check on the back. Obviously, it is not the powder charge.
 

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Rifleman97

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Dec 28, 2017
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It’s an old thread but there’s some good advice in there, other than the people saying to try a different powder, etc. OP on that thread had same issue as you.

For a TLDR of that thread; A couple people said lightening the crimp a bit can help, as well as aiming for 1200 FPS, as that’s the sweet spot for the 405’s apparently. There’s a decent amount of information there
 

catamountsierra

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Apr 18, 2014
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280
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Nampa, ID
Question: Is this one of the old Microgroove barrels? My family had one of those in 30-30 and it shot jacketed bullets just fine but couldn't hit the broad side of a barn with hard cast lead. It seemed like the rifling was just not grabbing the bullet and it acted like a smooth bore.
 

Les in Wyoming

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Oct 10, 2020
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98
Location
Glenrock, Wyoming

It’s an old thread but there’s some good advice in there, other than the people saying to try a different powder, etc. OP on that thread had same issue as you.

For a TLDR of that thread; A couple people said lightening the crimp a bit can help, as well as aiming for 1200 FPS, as that’s the sweet spot for the 405’s apparently. There’s a decent amount of information there
 

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