45-70 Trapdoor Loading

[NRAHighPowerShooter]

I didn't want to hijack the other older thread about using IMR3031 in a Trapdoor.
I have the 29.5" barrel 1883 Trapdoor and It won't shoot 405gr bullets worth beans... I tried anywhere from 32- 35 gr 3031
Then I buddy of mine had a few 500gr bullets and I couldn't find any data for that heavy of a bullet.
I did use 35gr 3031 and the riffle loved it!! A LOT better accuracy with the 500gr.
I did crono the load and it averaged 1255fps. Should this load be ok?

[Winger Ed.]

I'd recommend getting the Lyman cast book if you don't already have one.
It has a section on the 1873 trapdoors and data for loading the 480, 520, and 540s.

[M-Tecs]

Original TD's tend have large bores. 0.461" to 0.463" are common and I have seen one that had a 0.466 bore. Larry has some good info here.

https://castboolits.gunloads.com/showthread.php?190999-My-Trapdoor-Loads-Technique-and-Equipment

More on bore size

https://castboolits.gunloads.com/showthread.php?450170-Sprinfield-Trapdoor-45-70-questions&highlight=trapdoor+Springfield+bore+size

https://castboolits.gunloads.com/showthread.php?389870-Trapdoor-First-Timer&highlight=trapdoor+Springfield+bullet+recommendati ons

[Chief TC]

Original TD's tend have large bores. 0.461" to 0.463" are common and I have seen one that had a 0.466 bore. Larry has some good info here.

https://castboolits.gunloads.com/showthread.php?190999-My-Trapdoor-Loads-Technique-and-Equipment

More on bore size

https://castboolits.gunloads.com/showthread.php?450170-Sprinfield-Trapdoor-45-70-questions&highlight=trapdoor+Springfield+bore+size

https://castboolits.gunloads.com/showthread.php?389870-Trapdoor-First-Timer&highlight=trapdoor+Springfield+bullet+recommendati ons

Thanks for posting these M-Tecs. I finally was able to slug my bore and I got one the big ones at .464, so I have many adjustments to make now. I am researching Accurate moulds to be able to cast that large in the correct alloy and looks like 16-1 might be the better ratio.

[badwolf]

Lee 405 hollow base mold works well in mine, it expands to fill the bore especially with black powder. Spence wolf's book on trapdoor is great

[missionary5155]

Been with TD's near 50 years now.
1st, as with all barrels, measure the groove diameter ad fill it +.0015. The cast is your piston to seal the pressure behind the slug. Plus alot more.

[Chief TC]

Lee 405 hollow base mold works well in mine, it expands to fill the bore especially with black powder. Spence wolf's book on trapdoor is great

I did have a fellow range buddy give me some of his 405 HB loads and they did work well at 100 - 150. I prefer to use the 500gr bullets because my TD has the Buffington sights. I know you can adjust for the 405s but would rather use it as designed. I got the load dialed in but the groove diameter, so I hope to be able to produce some decent groups.

[Sgt H]

Based on what is posted on various boards, seems a lot of folks use 3031 in the 45-70. I have been loading the 45-70 for over 40 years but have never used anything slower then 4198, AA2015 or RL7. Even with those, which are faster than 3031 I did not get good results at trapdoor levels. Velocity spreads up to 200 fps. They did not burn efficiently until the pressures got up to 28,000psi or so. This seems to be the case with any of the single base extruded powders. Just my $.02.

[badwolf]

The 500 gr will bump up with black powder

[missionary5155]

Yes they will bump up. But badly undersized will also slump in the process of expanding. That lead comes from the front, nose area, which is the last section to get going.
So go for fit. First.

[Larry Gibson]

The 500 gr will bump up with black powder

Only if sufficient BP such as 70 gr is used.

[Rockindaddy]

M-Tecs: You are spot on! Most every Trapdoor I have ever owned had .461~.462 groove diameters. It is my contension that the US Army at the field trials of the Trapdoor in 1872 when they decided to change from 50-70 to a 45 caliber rifle; they should have called the new 1873 service Trapdoor rifle a 46-70 ! They are truly a .46 cal rifle. I have been experimenting with the Lee 400 grain hollow base mold and sizing them to .461 I had to make my own Lyman H and I dies for my lubricator-sizer. My groups are getting smaller!

[pworley1]

I have had good results with both 3031 and 4198 using a 405 hollow base sized to 461.

[Chief TC]

I have had good results with both 3031 and 4198 using a 405 hollow base sized to 461.

I saw in one of my reloading manuals using Varget for a 45-70 smokeless load. Anyone have experience with this powder in any of their 45-70 rifles?

[Larry Gibson]

I saw in one of my reloading manuals using Varget for a 45-70 smokeless load. Anyone have experience with this powder in any of their 45-70 rifles?

Doesn't burn "clean", even with a dacron filler, at TD pressure levels.

[Chief TC]

Doesn't burn "clean", even with a dacron filler, at TD pressure levels.

Thanks Larry. So when powder is not fully burned up, what issues/problems will that cause? Obviously it is a waste of powder and a dirtier barrel but anything else to consider? Thanks.

[Larry Gibson]

Just leaves a lot of unburned residue which is usually deposited in the action when the 45-70 case is extracted/ejected from the chamber of a TD. After a few rounds, if not cleared out chambering another cartridge can become troublesome. To get it to burn clean the dacron filler is a must and the load must be at the upper end psi wise giving velocities in the 1500+ fps range. The TD can be "uncomfortable" to shoot at those velocities with 400 and 500+ gr bullets.

[huntinlever]

Just leaves a lot of unburned residue which is usually deposited in the action when the 45-70 case is extracted/ejected from the chamber of a TD. After a few rounds, if not cleared out chambering another cartridge can become troublesome. To get it to burn clean the dacron filler is a must and the load must be at the upper end psi wise giving velocities in the 1500+ fps range. The TD can be "uncomfortable" to shoot at those velocities with 400 and 500+ gr bullets.

So Larry, what would be your recommendation? Clean the action (in my case, with the lever, removing the finger lever/ejector/bolt) after each few rounds, or burn at the higher levels (and is this specific to Varget, or most smokeless loads of a certain burning rate) in general?

[Larry Gibson]

Use h4895 or IMR 3031 with dacron filler in lieu of Varget.

[huntinlever]

Thanks. Burning rate? Given IMR 4198 is faster than 3031, would that be in the right direction as well?

[Larry Gibson]

Yes, 4198 is a "favorite" powder for many in the 45-70 with TD loads.

[huntinlever]

Yes, 4198 is a "favorite" powder for many in the 45-70 with TD loads.

Great, thanks Larry. Not that I'm staying there, but I plan on doing a ladder test with 33-37.5 grains 4198, curious on how things look, estimating 1500-1600 fps. I saw a post of yours on the Magnetospeed and ended up getting one. 30.0 grains 5744 also looked visually promising though I plan to do a similar higher series there, too. (29-33.5).