Rolling Block identification help

[Pathfinder]

Recently purchased what I believe to be a #1 Rolling Block chambered in 43 Spanish. Any additional information confirming or correcting this would be greatly appreciated. It did come with a m1871 first pattern bayonet.
I purchased a couple .43 Spanish cartridges on GunBroker from a collector that failed to chamber. So either they were not 43 Spanish, they appear to be 43 mauser, my rifle is not a 43 Spanish, or both.

Overall Length 50.5"
Barrel Length 35.25"
Muzzle .431"
Receiver 1.325" at the flats

These are the markings found when disassembled.
Upper and lower tang - 4510
Upper tang three lines starting with E Remington & Sons, the final patent date is illegible.
Barrel marking just before the receiver - B
Barrel marking under first barrel band - HP
Buttstock - 2
Forearm sling mount - Paid Feb 11th 1866

The receiver original finish was Case hardened as some of it still remains.

I have not "slugged" the barrel yet.
I did do a cast of the chamber and the dimensions are attached as an image.

That is all I have for information.

[Bill Allen]

It's not a 43 spanish nor reformado if that helps don't believe it's an egyptian The good news is this is the very best place to sort it out. Just went through the process myself good luck with it. Bill

[Pathfinder]

Thanks Bill. .43 Spanish was the closest I could find to the chamber specs from the cast I did. Hopefully someone else here might recognize the numbers.
Here are a few more images of this rifle.

[marlinman93]

This is a very strange chambering for the Remington Rolling Block you have considering the chamber cast measurements. It's closest to the .44-90 Sharps than to any Spanish variation of the .43 cartridge. I wonder if someone ran a .44-90 reamer into the chamber to open it up? Or if it possibly got some special chambering many years ago?

[Bill Allen]

The sad thing is somebody on this forum probably knows what it is but for some reason people read these posts but really don't seem to want to answer them (that said with a few exceptions) I'm just a beginner at this but I'll at least try to the extent of my knowledge. I looked through the cartridge book didn't see anything close but there in lies the problem I know mostly these things can be sloppy and I don't have the experience to know how much. Thanks Bill

[marlinman93]

I think you're correct Bill. Got to be someone who knows the answer better, or could contribute with a response to help.

[Pathfinder]

I hope you guys are correct. I have a few missions concerning this firearm... To figure out what this rifle is chambered in, to get more info about its origin, and lastly harvest something to fill the freezer with it.
Is there a source out there with data compiled on things like contract numbers and markings?

I am under the assumption that the numbers on the upper and lower tang are not serial numbers but represent the "lot" or contract for which that particular receiver was produced. So lot 4510 should mean something.

The only two markings on the barrel are B and HP, so not having a crown and some of the others I have come across rules it out as one of those rifles, I would think.

[marlinman93]

You're correct that the numbers on the top and bottom sides of the tangs are not serial numbers. They are there to keep the parts together during different phases of finish and fitting work. So it has nothing to do with dating these rifles or actions.
A lot of these military rifles don't have a serial number, but if they do it's usually on the exposed surface of the lower tang.
There are no records I know of for any early Remington Rolling Blocks, regardless of whether they're military or civilian models.

As for shooting this rifle, or loading ammunition for it; you could very likely use .43 Mauser dies and brass. The brass might be tough to find, but you can also get .44-90 Sharps brass from Buffalo Arms Co. and still use the .43 Mauser dies to load it. Just wont be able to full length size the brass, but that shouldn't be a problem with a single shot where you're only shooting the brass in the same gun all the time. I never full length size after the first time, and not even the first time if the brass fully chambers without sizing.

[Pathfinder]

Marlinman93,
I believe that 43 mauser has a wider case mouth than the 43 spanish neck. The two rounds that I purchased on gunbroker as 43 spanish actually measure out as 43 mauser. At least according to my franklin arsenal calipers. They do not fully chamber in my rifle, stopping where the case mouth makes contact with the neck of the chamber. It leaves about 3/4" of the cartridge protruding.
I will dig into info on the 44-90. There are so many numbers rolling around in my head right now I am forgetting what's what.

Are there any reliable sites that have chamber dimensions I can use?
I purchased the 16th edition of "Cartridges of the World" to be greatly disappointed as it just offers a general description of most of the cartridges.

[marlinman93]

The .43 Mauser does have a larger bullet diameter than the .43 Spanish. I believe the .43 Spanish uses a .439" bullet and the .43 Mauser uses a slightly larger .445"-.446" bullet?
Lee sells both die sets for the .43 Spanish or .43 Mauser at pretty reasonable prices, so whichever is closer would work for bullet seating, but likely not for full length sizing if your gun isn't one of the two cartridges.
But the .44-77 Rem./Sharps, and the .44-90 Sharps both use a much larger .451"-.452" bullet, unless it's paper patched. They use the same .446 for paper patched, which becomes a .452" with two wraps of paper. I shoot a .452" grease groove bullet in both my Creedmoor Roller in .44-77SBN, and my other Roller in the same caliber. I reload both using .43 Mauser dies because they were cheaper than buying expensive .44-77 SBN dies.

I've had a copy of Cartridges of the World for many years, and agree that it's disappointing in a number of aspects. Often with plain incorrect information as to bullet diameters, etc. It also lacks a lot of info I wish was in it. But it does often assist my search for data and what cases might work as donors.
I have Nonte's book on Cartridge Conversions also, and it's another good source, but sometimes it's old enough that the case he suggests using is also obsolete.

[Pathfinder]

Update:
I swear this thing is a .43 Spanish

Several books later, still no info as to its exact origins, I basically know more about what it isn't instead of what it is. That is progress in my book.

I have not found anything matching the specs from my chamber cast, with 43 spanish still being the closest.

Attached are images of a .43 spanish (top), a .43 mauser (bottom), and a side by side (mauser on left). I ordered both rounds off Gunbroker as .43 spanish.
The Mauser round does not fully chamber, however, the .43 Spanish drops in like a long lost friend.

[wlw-19958]

Hi There,

Your chamber measurements are consistent with the
same measurements of my chambers of the two rifles
I have in .43 Spanish.

Good Luck!
-Blue Chips-
Webb