Trapdoor Black Powder Reloading

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mr.tickle

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I had the bore slugged on my 1873 Trapdoor, it came out to .458. What size bullet do I use? .456, .458, .460? I was planning on shooting blackpowder cartridges. I am also not able to cast bullets at this time, so I will have to buy bullets. Is hard cast ok?
 
Hard cast is not ok with black, and you need soft BP lube, not the hard blue wax on most hard cast.
I have bought many bullets from Montana Bullet Works. Their "air cooled" with BP lube has shot well for me in .40-65.
Something in the 405 gr range would be correct for your 1873, maybe the 385 gr Lyman. .460" will be good in your .458" groove diameter barrel.
https://www.montanabulletworks.com/product-category/big-bore/page/2/?filter_caliber=45
 
Thanks! When shooting black powder do you always shoot a bullet size bigger than the bore? What would happen if I shot .458 sized bullets?
 
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There are a some pretty good blackpowder cartridge reloading manuals out there. One of my favorites is "SPG Lubricants BP Cartridge Reloading Primer" by Mike Venturino and Steve Garbe. Another one is "Loading the Black Powder Rifle Cartridge" by Paul A. Matthews. Yet another by Matthews is "Cast Bullets for the Black Powder Cartridge Rifle".

My experience with loading blackpowder cartridges is limited. I've done some for my Shiloh Sharps, but not much. However, I'm pretty sure that the answer to your question "Is hard cast ok?" is - It depends on what you mean by "hard cast." In general, I don't think the expert blackpowder cartridge rifle shooters use cast lead bullets that are quite as hard as most cast bullets for smokeless powder cartridges.

But maybe Dog Soldier will chime in here. I noticed in some of his posts that he hunts big game with a .45/110/500. No doubt he knows more about blackpowder cartridges, including bullets, than I.
 
They OUGHT to do ok. My .38-55 mould only casts about .0005" over groove diameter and the old Winchester does ok.
But my .40-65 Browning with a nominal .408" Badger barrel does its best with .411" which I figure is throat diameter that can be more important than groove.
Of course a Trapdoor is a military weapon and fine details that apply to sporting and target rifles don't matter as much. The worst thing that can happen is that you use bullets too hard and/or too small and lead the barrel.
 
Elmer Keith, a guy that did a lot of shooting and a lot of writing, says when
you shoot cast bullets make them groove diameter. Now he was talking
about pistols and that always worked for me. Chime in Dog Soldier after all
you have a lot of years of experience.
Zeke
 
I shoot the 405gr bullets from Missouri Bullets in my Trapdoor. I do shoot the 300gr bullets at times too. They are sized @.459" and they shoot VERY well for me. I'm not sure the lube is correct for Black Powder but if you call the owner he will help you with that.
http://missouribullet.com/results.php?pageNum_rsCWResults=7&category=6

In case you decide to use a smokeless powder, I use AA5744 and I'm very happy with that powder.
 
I never shot black powder ,but did shoot cast, with my Ruger single shot. Kept the velocity low for plinking. .001 or .002 above bore size worked best. I think it to avoid any powder gas getting past the bullet (not boolit!) and gas cutting it. If I pushed to fast or the bullet was too small had lots of leading and poor accuracy.
 
Mr.tickle: Trapdoor Springfield rifle bores are very difficult to measure accurately unless one has the proper 120 degree "V" micrometer because of their 3-groove rifling. A bit of research with trapdoor experts will convince you that your rifle is more likely .460-.462 "groove" diameter and a .462 or slightly larger diameter bullet will shoot most accurately. Of course, you can simply load black powder and very soft undersize bullets and that will probably work OK. If your rifle is a true 1973, they were made to shoot a .459 diameter, 405 grain bullet made from one part tin to 50 parts lead using 70 grains of FFg black powder. Usually a thin card wad was placed between the bullet and powder charge. I have dismantled hundreds of these original loads for museum exhibits and they are quite uniform. Lee precision offers a bullet mould that will cast a replica of this bullet and many trapdoor shooters have excellent accuracy with it. Going the smokeless powder rout is a whole other ball game.
 
I had CMP inspect and slug it so I am hoping they were able to measure it correctly. I am planning on only shooting black powder out of it. They said it swallowed a no-go and field gauge, so I am leaving the smokeless powder alone. While they wouldn't agree or deny they said I SHOULD be ok shooting black powder loads out of it.
 
I had CMP inspect and slug it so I am hoping they were able to measure it correctly. I am planning on only shooting black powder out of it. They said it swallowed a no-go and field gauge, so I am leaving the smokeless powder alone. While they wouldn't agree or deny they said I SHOULD be ok shooting black powder loads out of it.

I am going to give you the Company answer: Don't shoot it. You have a rifle that is known to be out of mechanical tolerance. The risk is that with excessive case head protrusion, you could have a burst case head.

These pictures came from Chinn's Machine Gun book, Vol IV. You should read the section on blowback to understand the concept of case head support.



The distances in this diagram relate to 20mm cannon shells, not 45/70 cases.



What may mitigate your problem is the construction of modern cases. Originally your Trapdoor fired balloon head cases which were very weak in the case head compared to modern cases. Modern cases are solid head cases with thicker sidewalls. But, I don't have any measurements nor analysis to determine just how much a modern case head can protrude from the chamber and not burst at blackpowder pressures. Nor have you provided any measurements about just how much headspace you have. Here is an excellent post on balloon head cases and headspace in Martini's.

Word of caution about balloon head cases

http://forums.gunboards.com/showthread.php?787-Word-of-caution-about-balloon-head-cases

You do not know the previous history of your rifle, it is altogether possible that the headspace is as it was when it was built or rebuilt. Or the headspace has grown due to previous owners shooting loads that were too high for the metallurgy of the period.

So, the company answer is don't shoot it. You have to decide for yourself what to do. If you do fire it, monitor the condition of the cases, see if there is any unreasonable expansion of the case heads, and always wear your shooting glasses!
 
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