First, I'd remove all the copper fouling from the barrel before shooting the cast.
For smokeless loads use a gas checked bullet.
Montana Bullet Works has both plain base and gas checked that will work for you. FWIW, he also has some good info in his FAQ section. He recommends gas checks above 1500fps with his big bore bullets that he alloys at 15bhn. He will supply with smokeless or BP lube.
Buffalo Arms Co is another one to look at for bullets. They also have the wads and other such stuff for BPCR duty, including paper patching if you ever decide to go that way.
Also from above, do your shooting with black or smokeless on one day. Clean, then use the other powder on another day. Two completely different lubes are needed and the fouling with black is something that needs special care. It will mess up a smokeless load.
As mentioned, you are simply pushing the 300 gr PB cast bullet way too fast. If it was a GC bullet and GC'd then it probably would shoot a lot better. If you want to use the 4198 powder with the commercial Meister 300 gr bullets drop back to 33 gr and use a dacron filler to lower the velocity to 1400 fps +/-. Better would be to try a powder on the order of Unique with loads starting them at 1100 fps up through 1400 fps.
The best option for "edge of the envelope" velocity with 300 +/- gr cast bullets is to get a mould for a GC'd bullet. I have found the RCBS 45-300-FN is an excellent one. That mould comes in both GC and PB form. The custom mould makers have similar moulds.
Larry Gibson
“Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
― Nikola Tesla
As others have stated, the OP is pushing the bullets too fast. However, tipping bullets are usually caused by a bullet which is too long to stabilize, so going to a heavier bullet is the exact opposite of the correct course of action.
But that isn’t the OP’s problem. If the bullets are indeed tipping at just 25 yards then they are being damaged in the barrel. Gas cutting of the bases, partial stripping in the grooves, who knows. But slowing the bullets down will help.
I had to laugh out loud at the comment that smokeless loads required gas checks! With almost 50 years experience with various .45-70s, most of my shooting has been with plain-based bullets. They shoot great if treated like lead boolits. Treated like jacketed bullets they usually failed. I have exactly one gas-checked .459” mould, the RCBS 405FN. My 30” Petersoli rolling block has a .454” groove diameter and shoots the gas checks better since I have to use .459” bullets to fit the throat.
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The mold Larry Gibson mentioned RCBS - .45-300-FN is the mold I have been using, Accurate or NOE probably have clones. I have purchased gas-checked cast bullets from Matt's Bullets for 35 Rem, 308, 32 Special, and 444 with excellent results, though his lightest GC 45-70 bullet is 365 grains. Also check with Bullshop bullets, used his bullets for 32 Special, 348 Win and 308/300 Savage, again excellent results, he has a very large selection that are custom cast for each order. There are some others that produce excellent bullets but these two have produced bullets that have produced many 1-1.5 MOA groups out of my 308's and 32 Special. There have been folks who put a 45 gas check cup side down under plain base bullets for the gas check effect. The gas check would need to be sized the same or maybe a thou less (.001") and seated by the bullet to be safe. A dacron filter or slow powder that is slightly compressed would work here. Some other folks load a case full of 4831 or other'slow powders, getting black powder performance without the mess, plenty of different techniques. My hunting load in my Marlin 1895 is 58 gr Accurate 2015, a Fed 215M Primer, W-W brass and the RCBS 300 gas checked flatnose or the Barnes Original(pure copper jacket, pure lead core) 300 gr. Recoil is brutal and trajectory at 9800 feet elevation is surprisingly flat(no air!). The Hornady, Sierra, and Remington 300 gr bullets are fine for deer but do not hold together for bigger stuff. Enjoy but do not let that rifle beat you up, this is supposed to be fun.
A belated thank you to all for your sage advice. I'll drop back on my velocity a good bit and start there, then work up until I hit the butter zone.
Welcome Sam !
Gas Checked boolits help a lot with getting an accurate load worked up .
Looking at RCBS Cast Bullet Manual , 45-70 loads and every boolet from 300 to 500 grs. is a Gas Checked design ... my tip-o-the day is try a boolit with a gas check .
I've always got better accuracy with 35 cal and 30 cal rifles when I went to one with a gas check .
Gary
Certified Cajun
Proud Member of The Basket of Deplorables
" Let's Go Brandon !"
Thanks, Gary. I have some Cast Performance 405 gr WNFPGC that I'll load to Trap Door velocity. My Lyman manual shows 35.0 IMR 4198 pushing a 405 gr boolit at about 1400 FPS. I may give that a try.
I see you're in Red Stick - so am I. I live in Rushmore, just east of Flannery on Choctaw.
I can’t add to the great advise given but I wanted to say hi. I grew up in Shreveport a few years ( some say many) years ago. I still chuckle and picture the team singing Hoo-dat.
The sooner I fall behind...the more time I have to catch up with
If the rifle is fairly accurate with jacketed bullets, those bullets are holding the rifling, or lands without stripping. If the cast you are shooting are not accurate they are not hard enough to hold to the lands at your current velocity, the bullets are stripping. Since you are buying factory cast, you do not have control of the hardness of the alloy used, leaving you with one control, the velocity. Try slowing the bullet down to see if the bullet then maintains proper rotation by the lands, without stripping.
I prefer sized to groove diameter, no more than .001 over and by your notes you are .0015 over. You could adjust this with a push through sizer, using case lube if you wish.
Hard cast, solid base, bullets do not obturate by any meaningful amount, they need be sized to the groove diameter or slightly larger before you load and fire them.
I cast my 458 bullets real hard, about 23bn powder coat them and push them hard in my 98 Mauser with R-7.
“There is a remedy for all things, save death.“
Cervantes
“Never give up, never quit.”
Robert Rogers
Roger’s Rangers
There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves.
Will Rogers
I'm in the Middle of the city ...in the old Capital Heights Subdivision , nearest landmark is Webb Memorial Golf Course ... about 3-4 blocks away . Have lived here in an old 1929 built house for 49 years .
You will find several natives roaming around the site , some still in LA but many have left the state .
Gary
Certified Cajun
Proud Member of The Basket of Deplorables
" Let's Go Brandon !"
I checked the bullet jump with the CP 405 gr boolits, and with the boolit seated right to the cannelure they're just touching the rifling. So I'm going to try some 1300-1400 FPS loads with IMR 4198 to see what transpires. After reading all the great input above, I think I've just been trying to push the cast too hard. BHN is stated to be 18-21 - their website claims that they have fired their bullets at velocities as high as 3100 FPS with good results. Of course, that might be with .30 caliber boolits.
I won't say I don't like some folks, but I would unplug their life support to make a pot of coffee
I saw it mentioned earlier, Unique is a great powder for cast bullets. I shoot 15 grs for 300gr cast slugs, with great accuracy, and they have done well on deer here in KY. The deer I have shot were from 70-125 yds, drilled thru both shoulders like butter, and you could eat right up to thve hole with not a lot of bloodshot meat. Deer did not go anywhere. Recoil is very light. Welcome to the site, we will treat you so many ways you will have to like one of them.
The load I use in my marlin 1895 cowboy
31.5 grains of I4198
Lee 405 HB
Will do 2" groups @ 100 yards with irons.
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |