Hi.  I have a rolling block I recently acquired which is puzzling me.  I bought it for deer hunting in thick brush and I think it will do well as an alternative to my Trapper Winchester 94.  That said, I am having an identification issue.

It is a carbine.   It has (for unknown reasons) been excessively sanitized by someone long, long ago.  There are no visible markings other than a very faint trace showing it once had tang markings.  It is nickled.  The nickeling appears to have been done in the 20th century as in places it wears (such as on the block, I see copper plating underneath and that process combination is WWI era, not 19th century) I have Mr. Layman's book and can tentatively (assuming the rear sight is an original and not an add on) id it as an Argentine '71 (with a bar eztractor)based only on the external appearance.  However...

I did a chamber and bore cast with Cerrosafe.  The bore is .435 with grooves of .433.  

The chamber is that of an unknown to me cartridge.  The chamber walls are straight for a rimmed cartridge.  There is no free bore in front of the chamber edge.  A .43 Spanish will not enter the chamber, too fat.  Of course this also knocks .43 Reformado out of consideration also.

Chamber length: 2.21"
Neck diameter: 0.468"
Base diameter (just forward of rim): 0.476"

The lack of a free bore to me means the actual cartridge is a little shorter than the chamber area as otherwise the bullet would jam against the rifling and the action wouldn't close.

Brass from .45 Colt will not enter the chamber (too fat), but .44 magnum brass will.  I experimentally loaded some 44. Magnum brass with black powder and under a (.435) 44 Henry bullet and it shoots fairly well.  LoL, so too with .442 Webley (with the 435 44 Henry bullet) and 44 Russian, and also 44-40 (however my reading indicates the RB carbines in .44-40 (44 WCF) have a much shorter chamber than my gun does).  I moved on to .444 Marlin brass and immediately ran into the free bore issue.  Using pulled bullets from an original .43 Spanish cartridge (which actually measure .429 with a slight skirt at the base and a weight of 370 grains) on the .444 Marlin brass the rifling engages the bullet about 2mm above the case rim (picture).  Switching back to the pistol bullet (seated deep) allows the round to be chambered and fired with rough extraction due to expansion of the 444 case neck (loaded dimension at the neck is only .451" which means the case has to swell 0.017" for a good fit.

Here is the 370 grain bullet seated on a 444 Marlin case and we can clearly see where the rifling engages the bullet and prevents the breech block from fully closing without excessive pressure being applied.

Where the nickel wears, the copper underneath shows

Front sight appears to be appropriate to the action.

It may well be that the rifle was previously chambered in 43 Spanish but some bucko lopped off the chamber end of the barrel, rethreaded the breech end, and chambered it to his idea of a cartridge with easy-to-find brass.  If this is the case, I wonder why not full length 444 - perhaps to prevent the chambering of a full-pressure 444.

Of course, you could use shortened and fire-formed 444 brass and neck size with an appropriate insert in a Meacham neck sizing die.  That way, the mouth of the case wouldn't have to obturate so far to seal the chamber and prevent so much blow back.  Oh, and a mold from Accurate Bullet Molds of the proper diameter with a meplat designed in for effectiveness on game.

Looks like a fun hunting rifle if you get it sorted out.

If somebody cut the barrel breech off and rechambered it, they did a fantastic job of aging the new surface to match the rest of the gun.

Could it be one of the Comblain cartridges?  The specs in the references don't match your chamber very well, but a friend had a Comblain rifle.  He managed to wangle a few reproduction cartridges and fired them.  They were bottlenecks when they went in but came out straight, and after some research he found that the chamber was correct and that's what the cases were supposed to do.  Soldiers fired them and tossed the cases, so it didn't matter.  Don't have a clue what that design was supposed to accomplish, but there it was.  A similar amount of "slop" might be included in the other dimensions as well.

He stopped shooting the gun because he didn't want to "overwork the brass" when reloading it.

There's a Comblain shooter on the Cast Boolits site; if your gun is close, maybe you could compare notes with him.

So what I seem to have is a Light Baby Carbine (LBC) to which someone has attached the wrong rear sight.  The rear sight should have smaller ears and 600 yard markings, not the 500 yard markings of the Argentina carbine.  

The military version of the LBC was offered in only 2 calibers.  44-40 and 44 rimfire.  Civilian versions were offered in calibers from .22 on up to .44-40.  Civilian versions mostly had octagonal barrels.  Only about 5,000 total were built.  Uruguay ordered about 3,500 in saddle ring carbine configuration and in 44=40.

When I fire 44=40 ammo in the gun the case walls blow out straight and it looks just like one of the fired 44 Magnum cases.  Based on the frame measurements I must conclude this frame and barrel is indeed a 44-40 chambering.  I would of course be a lot happier with that determination if someone out there with an original 'Light Baby Carbine' of known provenance did their own chamber casting and posted the results.

Now as to the question of why Remington cut a .44=40 chamber so deep, I have no idea.  I am thinking the most efficient loading is as I have been doing with cut down .444 Marlin brass, perhaps mostly with the 200 grain pistol bullet.  I will do some chronograph testing when this local rainy spring (26 of the past 30 days have been rainy days) converts to a dry summer.

measurement at a different point