Trapdoor Rifles

Hey everybody. I just recently purchased a weird gun on gunbroker.
Have wanted a Trapdoor for a long while, and had been looking for the older 50-70 versions. More smoke and fire seems like more fun.

Won this one, and everything mostly looked correct for an 1868 model 50-70 trapdoor. It was only missing the front barrel band. Cleaning rod, stock, lock, receiver, dates and markings all seemed to match up to early 50-70 guns.
Got the rifle in, and tried to chamber a 50-70 dummy round. No go. A set of calipers to the muzzle end of the bore show 45ish. A little weird, but not crazy, figured someone just swapped out to a later 45-70 barrel.


Then I started to do some more research. Looks like the rear sight matches early 1873 guns, expected for a 45-70.

This gun has the long nosed receiver however, and as far as I can tell, there were only ever 50 cal barrels fixed up to these. You'd have to make a custom barrel with longer threads or do some interesting machining to the receiver to make an off the shelf 45-70. Guess you could also potentially add more threads to a 45-70 barrel. Not really sure.
Also weird, are that there are markings that match on the barrel and the receiver. Couldn't find much out there that shows how barrels and receivers from the bottom. Anyone know what these are? Are these Springfield marks, or something added later?
Strangest of all, is that the caliber isn't a 45-70. I slid a 1mm carbon rod down the chamber so that I could catch the lip before the bore to get an idea of what it was. Problem is, the length was around 2.5 inches. Figured I'd better look more closely so I cast the chamber with some beeswax.

Chamber length from the front of the rim to the bore is 2.534. Base Diameter is .~.517, and bullet end ~.482. Seems like long 45-90 dimensions, or maybe closer to 45-100.

I know the army made some 45-80-500 guns that used 45-2.4" cases. Don't know how long the chamber was actually cut in those guns.

Is this some early 45 cal test gun, or just a random pile of parts? Buffalo gun? Seems like they've been assembled together for a very long time.

Well, long story short, it's pretty well got to be a pile of parts. Not to chide, and I do NOT say it meanly, but you really should have seen the '73 sight with the long receiver as a HUGE red flag to it being any sort of "official" model. Everybody under the sun fooled with trapdoors when they could be had for a dollar each or less. I think it is safe to say that the 48|48 was done by whoever did whatever they did to make the barrel fit the receiver. It is not a standard SA font, and the alignment mark is too crude as well. As an aside, I have a very early Model 1870 (short receiver) with .50-70 barrel stamped 77|77 but in the distinctive serifed font used on the M1868s, and with proper witness mark, so am fairly sure THAT was done at SA, so, the numbering idea WAS used when parts needed to be kept together. Does the receiver have a serial number?

Cannot address the caliber issue. Anything other than .45-70 (2.1") or .45-80 (2.4") would be off the wall. Yes, maybe a home-made "buffalo gun" could be a possibility. I think we can rule out any of the SA caliber-test arms, given points noted above. Although some early long-range rifles were made with long throats, I believe that when they settled on the longer case, the throat was "normal" (i.e. 0.3" longer than for a .45-70). Does your barrel have the standard 3 lands and grooves, 22" twist? Are there any remains of the V P eagle-head markings ahead of the receiver on the left side above the wood?

As you say, it looks, from a distance, to be a Model 1868, except I'd question the cleaning rod - hard to see in the one pic, but it doesn't look right. Is there a proper (matching, single vs. double, rod keeper in the stock?

FWIW, and I have never had it apart, 40+ years ago, I too acquired a gun with a .45 barrel in a '68 receiver. It is an obvious Bubba with pistol-grip stock having a schnabel forend and Lyman tang sight, which I put aside to shoot (bore is pristine+) but never have gotten around to doing so. I will try and find it, and check the bottom for markings, just for fun. I do not know how they mated the parts.

There are MANY mysteries in trapdoorland - you have found one!

Dick Hosmer wrote:Well, long story short, it's pretty well got to be a pile of parts. Not to chide, and I do NOT say it meanly, but you really should have seen the '73 sight with the long receiver as a HUGE red flag to it being any sort of "official" model. Everybody under the sun fooled with trapdoors when they could be had for a dollar each or less. I think it is safe to say that the 48|48 was done by whoever did whatever they did to make the barrel fit the receiver. It is not a standard SA font, and the alignment mark is too crude as well. As an aside, I have a very early Model 1870 (short receiver) with .50-70 barrel stamped 77|77 but in the distinctive serifed font used on the M1868s, and with proper witness mark, so am fairly sure THAT was done at SA, so, the numbering idea WAS used when parts needed to be kept together. Does the receiver have a serial number?

Yep, I should have caught the sight thing. I will admit to not knowing enough about trapdoors when I bid on this. Not discouraged at all though, I just wanted a fun old gun to make smoke with, figured I'd learn more about the rifles with one in hand. There is a ton of information out there to process. The price was also very right, though not as good as a dollar. I'm too young to have gotten anything near that deal.

For fun, I chunked some numbers into an inflation calculator. The amount I paid for the gun would have been $22.50 in 1863.


Receiver does have a serial number, a 12XXX range that seems to fit with an 1869 breech block according to Frasca's Springfield Book II. Just got it yesterday, so I'm learning a bunch.

Dick Hosmer wrote:Cannot address the caliber issue. Anything other than .45-70 (2.1") or .45-80 (2.4") would be off the wall. Yes, maybe a home-made "buffalo gun" could be a possibility. I think we can rule out any of the SA caliber-test arms, given points noted above. Although some early long-range rifles were made with long throats, I believe that when they settled on the longer case, the throat was "normal" (i.e. 0.3" longer than for a .45-70). Does your barrel have the standard 3 lands and grooves, 22" twist? Are there any remains of the V P eagle-head markings ahead of the receiver on the left side above the wood?

There is a V marking ahead of the receiver as you can see in the above picture. That's the only other symbol on the barrel aside from the 48 on the bottom. It's got a 3 groove barrel, and the twist rate seem to be between 22" and 23". I tried to slug it, but it's kinda impossible to measure. I can't find any part thicker than .456ish with a pair of calipers. Will probably slug it again now that I've cleaned the bore up more.

I am pretty sure the caliber is .45-100. Here's a picture of the wax chamber casting measurement. Would have made more sense to me if I remembered to add the rim thickness to the number. The chamber is just a few thousands longer than 2.6 inches. To further verify, I drew up a .45-100 case in CAD yesterday, and added a 500 grain long range bullet as it would be seated in the shorter 2.4 (45-80) case. I 3D printed one out, and chambers just fine. Not sure if it will eject well though, it's pretty long for the action.
I ordered some 45-2.4" brass, as the longer stuff seems impossible to find at the moment. It should work well enough if I seat a long bullet out long enough. I plan on using black powder. Will just need to clean the chamber well after every session until I can find some longer brass.

Dick Hosmer wrote:As you say, it looks, from a distance, to be a Model 1868, except I'd question the cleaning rod - hard to see in the one pic, but it doesn't look right. Is there a proper (matching, single vs. double, rod keeper in the stock?

FWIW, and I have never had it apart, 40+ years ago, I too acquired a gun with a .45 barrel in a '68 receiver. It is an obvious Bubba with pistol-grip stock having a schnabel forend and Lyman tang sight, which I put aside to shoot (bore is pristine+) but never have gotten around to doing so. I will try and find it, and check the bottom for markings, just for fun. I do not know how they mated the parts.

There are MANY mysteries in trapdoorland - you have found one!

You are probably right about the cleaning rod, it's a bit bigger on the head than a 50 caliber. It'l go down a 54 cal barrel, but not a smaller one. It's probably a 58 musket cleaning rod. At the time, I was going on pictures on the internet. Saw several of the older 50 trapdoors with rods that looked like this. Wouldn't surprise me if they had the wrong ones also.
I will just have to keep learning. I had planned on buying a couple trapdoors, one a 50, and one a 45. Now I think I'll have to end up with 3. See if I can't get a proper 50 and a proper 45 to bookend this oddball.

Now I know this is likely a pile of parts, I need to decide what to do about a front barrel band. I'd like a front sling loop. This stock doesn't have band retention springs, which I think was normal for some of the previous muskets. Haven't figured out yet if any early trapdoors were that way. Some unconfirmed info on the net said yes, but that's not a trusted source. Wondering if it'd be blasphemy to install retention bands. Maybe I can find a band that will fit the front that doesn't need them, and comes with a sling mount.

Thanks a lot for the help!

The rod is from a M1855-1861 Springfield musket.
Frankly, nothing you do to this gun will be blasphemous, so do as you please and enjoy having and using it.
The remaining "V" would be consistent with a M1873 .45 caliber barrel being modified to fit into the longer M1868 receiver.

Since there is no cleaning rod retaining spring in the gun, a regular trapdoor rod will slide out when firing, so it would be easiest to remove any rod before firing.

You could add band springs if you, it is not that hard, other than careful layout to ensure the hole for the spring pin is the correct distance forward to fir the band, and that it is low enough to not hit the bottom of the barrel.

Yes, with the spoon cut, that is a musket, or early .50-70 stock. Some muskets, and the '68s used clamping bands (though only at the rear in case of the '68, which had a conventional spring-retained band at the front). I'd suggest installing one of those, as well as a rod keeper for a .45-70 rod. Not hard to find, or do. You have a good point about the .45-100 being too long to eject. I'd also wonder about the wisdom of using that much powder in a TD action, especially one where the barrel receiver joining isn't arsenal. In any event, it should be a fun project. Please feel free to ask any question, any time. Welcome!

John S. wrote: ↑Tue Jun 06, 2023 4:15 pm The rod is from a M1855-1861 Springfield musket.
Frankly, nothing you do to this gun will be blasphemous, so do as you please and enjoy having and using it.
The remaining "V" would be consistent with a M1873 .45 caliber barrel being modified to fit into the longer M1868 receiver.

Since there is no cleaning rod retaining spring in the gun, a regular trapdoor rod will slide out when firing, so it would be easiest to remove any rod before firing.

You could add band springs if you, it is not that hard, other than careful layout to ensure the hole for the spring pin is the correct distance forward to fir the band, and that it is low enough to not hit the bottom of the barrel.

Makes sense. I've ordered a couple spring pins. Will have to see if I can find some good pictures of what it looks like with them removed. Then practice installing some into a piece of 2x4. Or better yet, an old weathered piece of wood with similar looking grain structure as the stock.

Dick Hosmer wrote: ↑Tue Jun 06, 2023 5:37 pm Yes, with the spoon cut, that is a musket, or early .50-70 stock. Some muskets, and the '68s used clamping bands (though only at the rear in case of the '68, which had a conventional spring-retained band at the front). I'd suggest installing one of those, as well as a rod keeper for a .45-70 rod. Not hard to find, or do. You have a good point about the .45-100 being too long to eject. I'd also wonder about the wisdom of using that much powder in a TD action, especially one where the barrel receiver joining isn't arsenal. In any event, it should be a fun project. Please feel free to ask any question, any time. Welcome!

I'll see what I can find on rod keepers. Could also just modify the rod I have. It's so horribly pitted on the end, that grinding it down to fit, and then matching the remaining finish could be a mercy. Not that I'll use it unless absolutely necessary. Got plenty of softer cleaning rods than a steel one.

My 45-2.4 brass arrived, at the very least, it ejects just fine. I've also ordered some 45-2.6 snap caps to disassemble and play with. Only way I could get brass, it's new Starline stuff, so should be fine for actual shooting. Waiting on on a Lyman black powder manual so I can take a look at pressures before loading any of the big cases. Intuition says I'll likely have lower pressures with the larger case as long as I don't go crazy on powder load. Will be worth looking at a manual first though.

The 45-80-500 loads apparently moved at a pretty good clip.

https://www.oldammo.com/october05.htm

I will try and stay under those. I'll probably just be poking holes in paper with it after all. The action locks up very tight, no wiggle at all. The only potential weak point as you pointed out could be if the barrel install was done wrong. At the very least, with the longer nose, it has the potential to be a better connection if it was assembled in a sensible manner.

My second attempt to slug the barrel went much better. I had never tried to do it before, and either the bore wasn't quite clean enough, or my slug wasn't optimally shaped. I was worried about it being too hard to drive down the barrel the first time. Second attempt with a bore as clean as I want to get it, and a bigger slug shows the rifling much more clearly.

Spinning the bullet gently in a set of calipers gives me a groove depth of .4590. Which sticks it within the typical trapdoor range. The caliper method probably isn't the most precise, so the groove depth could likely be a bit bigger. Largest diameter bullets I can find for sale are some .460 500 grain ones from Buffalo Arms. Might buy some of those to play with. If accuracy is terrible, might have to get a custom mold and try my hand at casting.



Thanks for the help guys!

A lot of people go ga-ga over measuring TD barrels because they get in a panic over the dreaded ODD number. The sky is falling, the sky is falling, etc. . .

And, for (almost?) every other "odd" barrel they'd be right. BUT, the TD has three EQUAL lands and grooves. THEREFORE a "high point" to "high point" measurement IS possible! All you have to do is make a fine line or scratch on one mic jaw, then be sure that one of the striations on your slug is exactly on it when you measure. Many barrels go over .458/.459, but with a soft lead (20-1 or better) the bullets will 'bump up' to fit.

When EVERYTHING is perfect AND the gods are smiling, the TD will hold MOA to at least 200 yards. Our own Tom Trevor has done it!

Incidentally, I thought the same thing about the receiver/barrel overlap on the one I have - but it is well known that post-1873 steel (the process was changed) is considerably more uniform as to grain structure, hence stronger, so the point may be moot. In any event, common-sense loads should be fine.

Dick Hosmer wrote: ↑Tue Jun 06, 2023 11:12 pm Incidentally, I thought the same thing about the receiver/barrel overlap on the one I have - but it is well known that post-1873 steel (the process was changed) is considerably more uniform as to grain structure, hence stronger, so the point may be moot. In any event, common-sense loads should be fine.

Yeah, may not make a difference. I'll just keep my loads gentle. Well, gentle for a 45-100. Anything 500 grains is gonna kick a bit.

Got all the rest of the components I needed, as well as a new firing pin today. Forgot to mention the old one was broken. It was the old style, with a sharp transition/recess cut for a return spring. I've got a new style pin in it now without the spring. May or may not search for another old one.

Loaded up 4 rounds to test with. Need to find more brass.

45-100 / 42-2.6 Brass
80 Grains Grafs/Schuetzen FFg
.060 Veg Fiber Wad
500 Grain .460 Diameter Long Range Bullet
CCI 200 Large Rifle Primer

I get just a tiny amount of compression of the powder with the bullet seated like so. Should be a pretty safe test round. Figured it was better to have a little more powder, that to leave any empty space in the case. 80 was as little as I could get and make sure capacity was filled.

The gun actually ejects 45-100 cases just fine. It may not be as energetic as the lighter shorter cases, but it's serviceable. We'll see if it works as well with fired cases.

Here's a link to a really short video clip ejecting a 45-100 snap cap for those interested.

45-100 Trapdoor Ejection

Took one shot at the range, it fired and ejected fine, however the brass expanded more than I was hoping to see. Couldn't find much for actual chamber specs for trapdoors, and was unsure how much they increased the size to accommodate black powder fouling. Looks like whoever cut this chamber probably pushed it too far.
As I mentioned in the first post, base diameter of my wax casting was .517. Case specs according to web-searches for the modern 45-70 family seem to have base diameter ranges from .505-.508. Guess that's too much of a differential.

Maybe they didn't care as much back when copper cases were common, or maybe there wasn't as much reloading, or it was just cut wrong. I suppose it could actually be cut for a different cartridge. Not sure what that would be though. Anyone got any ideas?

I tried to make a bunch of cerrosafe casts with little success for a complete chamber, there is a bit of pitting towards the bullet end of the chamber that I think makes things difficult.

However, I trust the wax casting for length, and the bullet end of the fired brass formed nicely to the chamber to allow for good measurements. I had better luck with partial cerrosafe chamber castings, and got a solid measurement for the base diameter. It also seemed to be straight tape, and was nice concentric. No bulges in the actual chamber.

Here's the specs:

Length: 2.604"
Neck: .481
Base: .520

Any ideas about what's going on here. Could this be some different cartridge, or was it just poorly cut?

Wondering what I should do here. Guess it could possibly be re-chambered, or completely re-lined. If I go that far, wondering what caliber it should be. Will need to look and see if the barrel external diameters were different between 50-70 and 45-70. If not, I could have it returned to a caliber more fitting the receiver and stock.

The other option could be finding some other rimmed cartrige that's close, and seeing if I could make it work. The 450 Nitro Express No. 2 has a base much closer to my chamber. Perhaps I could cut it down and taper it back to 45 somehow.

I do not know how much expansion you are comfortable with, but, since this rifle is unique, the cases will "fire-form" to it, and you'll only need to neck size from now on, thus not repetitively 'working' the thicker/stronger rear of the case.

To answer your other question, yes, .45-70 and .50-70 barrels DO have different external diameters.