Reloading questions for 0.50 Rimfire Remington Rolling Block Carbine

I just bought sight unseen a Remington RB carbine. It was advertised as.50 calibre and ‘good for its age’. On first examination it looked pretty grim but while this gun has I think, lost its historical/collector value, it does have potential as a shooter. I want to shoot it but here’s the rub. In finding or creating a cartridge which will shoot – there are two main issues. First, it has a rim-fire block, and second, while it is notionally 0.50 calibre, (i) the bore slug gives it a groove diameter of 0.534 and a diameter of 0.517 for the lands and the chamber cast shows (Ii) the original cartridge is straight walled and possibly as long as 1.5 inches from its base to the commencement of the throat at the chamber, and (iiI) at 0.660, the rim diameter is exactly the same as that for the 50/70 Government cartridge. See attachment.

I can identify no rimfire cartridge (Spencer, Joslyn etc.) whose specs may have been a match for this chamber and upon which I could base the conversion of a centre-fire case to suit, although the 56/56 Spencer comes closest. Because of the suitability of the common rim diameter to the 50/70, I then thought the 50/45 or 50/55 centre fire cases which the 50/70 is based on might have specs which match instead. But they do not – for the simple reason their bullet diameters are about 0.515 – projectiles which are way too small for the bore on this gun.

The best I have been able to come up with for the moment is to paper patch (using .008’ paper) the 0.500’ 400 grain bullet I use in the 12.17 roller, to bring it up to 0.532 diameter. This seems to fit pretty well, although whether the patched bullet would work in a somewhat rough bore is a question for the future. I used this patched bullet to slug the bore and it seemingly was a very good fit. Somewhat hard to drive down the bore, but it picked up the rifling completely and afterwards measured the same groove and land diameters of the casting. So this is one possibility. However, if I was to base the proposed cartridge on a shortened 50/70 case and this bullet (patched or plain), the case would probably have to be substantially shorter than 1.48 inches if it was to have a wide enough throat to accept the bullet. That in turn would present the question of how much powder such a shortened case could carry under a bullet of that length and diameter. Another possibility is to do a little reaming to have the chamber extended to take a longer case. These are considerations I have to work on some more. But any assistance in getting me along the road to getting this thing shooting (the areas of uncertainty I have are captured in the questions below) would be greatly appreciated.

(i) What is the original rimfire cartridge this gun was chambered for – and does anybody have any specs for it in terms of physical dimension s, bullet weight and shape and powder charge,
(ii) Has anybody successfully prepared a cartridge for the 0.50 calibre rimfire,
(iii) Other than the 50/70, does anybody know of a donor case suitable for conversion,
(iv) Is there a mold (mould?) of suitable bullet shape, weight and diameter out there I might be able to get my hands on,
(v) I will need to convert the block from rim to centre-fire. Do-able of course but is there any intrinsic value of this rimfire gun which suggests it would be better to obtain a centre fire block and using it instead,
(vi) Has anybody any experience with the block castings available from The Rifle Shoppe – how much fettling is involved in getting them to fit and work,
(vii) Does anybody out there know where I can get a used #1 centre-fire block for a #1 Roller?

My own opinion is that to modify the roller to centerfire would be expensive unless a replacement breechblock could be found. bullets and brass is another consideration and I would imagine somewhat expensive as well. There is probably european brass that might be modified to work. In the end you will wind up with a rifle that has been modified from the original. I would just keep it as is for historical purposes. I have a roller in .50 carbine that is centerfire with the Navy anchor on the barrel. Fun to shoot no doubt. It uses 50-70 brass shortened and they work well in the 50-70 trapdoor I have as well. What I have found with rimfire rollers is they are low pressure affairs usually loaded with 1F powder.

Are you sitting tight? I don't want you to fall off your chair laughing!

It seems to be a Caliber .52 chambering, not a Caliber .50!

The ONLY candidates I can find are on P136-7 of "The American Cartridge" by Charles Suydam.
Group 61:
No. 1 Sharp & Hankins Carbine: rim/ bullet/OAL/case .633/.543/1.676/1.133
No. 2 Sharp & Hankins Rifle .640/.538/1.756/1.153
No. 3 Sharp & Hankins Rifle .645/.549/1.771/1.158
No. 4 and 5: OAL too long

Bullet weight would be around 400 gn. With BP, the bullet should be seated to be about 1mm (1/32") off the lands. Go much closer with BP and you are likely to have chambering problems with a dirty bore/throat. Pick case length accordingly, for adequate seating of the bullet.
Powder charge = fill it with Swiss No. 4 (1-1/2 Fg) with an overpowder wad.


P.S: Cancel the Sharp & Hankins option. Layman has no mention of this calibre being used in RBs

- or, just possibly, a 54 Ballard (Old Rifle or Carbine) !!! (see P.138 of the book)
- or, just possibly, a 56-52 Spencer!!!
- or even a 56-56 Spencer!!!


All these are so close together, and the known specimens in the book show such variations, that some dimensions overlap and very precise measurement of the chamber cast is required.

In particular, please measure the HEAD diameter from your chamber cast. This is a vital dimension for narrowing the range of candidates for the original chambering, AND for selecting a donor case type.

A 32 cal brass shotgun case is probably going to be your best bet for a donor case for any of the above possibilities. Get one and see how it fits!

I admit to having had a bit of a laugh at the idea that this darned thing may have been deliberately chambered in a damfool calibre so as to deliberately get up my nose 150 years later. But thanks to both of you for your input and efforts. In truth, the gun has no collector value. It has no markings anywhere other than a glimpse of a two-line Remington address on the upper tang. Oh yes, there is a 'u' on the barrel band. It is not a cut down rifle, but it definitely started life as a rifle action - it still has the threaded plate for the cleaning rod in front. Someone in its history badly blued all its metal surfaces, so with its originality gone, I have no hesitation in doing further mods to make it a shooter. Bubba made the oversight of forgetting to sand its wood which are in pretty good shape. So I've removed all of the blue using commercial rust remover to render it completely in the white - a great improvement, and a couple of divots in the stock I have repaired with old walnut. It is looking OK now. I'll see if anybody else can offer any more assistance with shooting it with the bore as it is, but if not, it is likely to be resleeved in 50/55 or 45/70.

The U on the barrel band strongly suggests a one-time military gun. The U was to be readable when the rifle was racked, i.e. it shows that the barrel band is the correct way round.

Don't go to all the expense of resleeving the barrel. Please read my posts on the Pickelgewehr (search) to see that one can, with a bit of luck and elbow-grease, bring back some barrels from the dead. If the bore shows that it is worth shooting, cut 32-gauge shotgun shells to the length as determined above, and use .54 cal minie bullets for muzzle-loading rifles! You will, of course, have to convert the block to centerfire, or find a replacement, but that is going to be easier than making rimfire cases! (Been there, done that - for my rimfire Peabody - it's a PITA).

Patrick thanks for that. Having looked at Your work on the other gun and your recommendation that I hold off resleeving mine, I've attached a few photos, both of the gun and its bore so you can see what I'm dealing with. The bore in mine in fact, is better in real life than the photos suggest. It actually has pretty fair rifling and some shine along its length as well as a few pits and roughnss - but certainly enough of a bore remaining to justify trying to make it work at the calibre it is. I'll cast about for some .32 gauge shotshells and the minnie you suggest. But the other idea I'm running with is to first get it centrefired and then fireform some shortened 50/70 cases and shave them back enough for the expanded case to accept the patched bullets I'll make. If that works, it is game on. If not, then the .32 cases.

The distance between the bae of the chambered patched bullet and the breech entrance is about 0.880". Add that to the seating depth of the same bullet of 0.457" and i have an indicative fireformed case length to accept that bullet (or your 0.54 minnies) as well as chamber properly, of about 1.4 inches. In point of fact there's little to be gained in expending more cash than the thing is worth just to get it shooting in another calibre, so it is a case of do or die with the existing calibre (whatever that is).

"...while this gun has I think, lost its historical/collector value, it does have potential as a shooter..."

Hey! I disagree! That ain't no Bubba job, that looks like an original military RB carbine. Historically interesting indeed and, yes, it ought to be shootable.


Before you do ANYTHING irreversible to that rifle, I think you ought to (no, make that MUST) get hold of "Remington Rolling Block Military Rifles of the World" by George Layman and read up on RBs. Rbs WERE made in 50-52 (Cuba and Puerto Rico), 56-52 (Peru) and 56-50 (Mexico) rimfire chamberings. It has NOT been Bubba-ed. In fact, because it is a rimfire, it has probably had a long, long rest. Schuyler Hartley & Graham appear to have shipped RBs, both rifles and carbines, all over the place, including Korea and China, and just about everywhere south of the border!

Patrick I'm not going to change anything on the thing - and thanks for your input. I've more or less abandoned the idea of resleeving or rebarrelling it, having discovered that the cost of doing so is pretty hard to justify. You correct me if I am wrong, but I assume the loss of its original finish with a reblue now removed, has turned something which was once collectable, into a presentable, shootable wall-hanger, nothing more. In any event, getting it to shoot is the end-game, to which end sourcing a centre-fire block and making up cartridges on the basis of what we have discussed is the strategy now. Let's see how things develop. BTW, what are the specs of the .32 shotgun case that give it application here?