For those that haven’t seen this yet .251 TCR (Tinker Centerfire Rimmed) is a wildcat I have been playing around with for a while. The concept is a centerfire round for revolvers that can be loaded in a power range from .22 CB Short all the way to .22 Magnum power levels. A 35gr. Speer Gold Dot loaded to 1000-1100 fps would make an excellent small-game bullet, and loaded to 950 fps or so might offer enough penetration for self-defense use. 50gr. FMC would have it’s uses too, especially when a less destructive bullet was desirable for small animals. If I’ve done my math correctly 1100 fps should be doable with a 50gr. bullet, even from a short barrel. Load a .25 caliber Airgun pellet over a primer and you might have a nice indoor target/vermin shooter.

Sometime back an online pal sent me some .22 Hornet brass to convert, which resulted in a handful of cartridges like the one pictured above (with a .38 Special cartridge for size comparison.)  Only problem is there’s no gun to shoot them out of. The eventual gun I want to use is a centerfire Single-Six, but initially I planned on re-barrelling one of my home-made single-shots for testing. Somehow this never happened, and budget issues being what they are the project stalled for a while.

Then I did a trade, and as part of that the gent threw in a replica Colt 1849 Pocket.

I considered a cartridge conversion to .22, but I’ve been there and done that. I also thought of a .32 S&W, but I was dubious about the chamber-wall thickness. The it occurred to me- chamber it for .25 Auto, get it all working, and when I can afford some gear to help reload .251 TCR bore the chambers out for that!  That way I could have a test-gun much cheaper than a Single Six.  Obviously the .31 caliber cylinder wasn’t going to work, and I really wanted something a bit stouter than whatever mild steel the original was made from. I turned a new cylinder from half-hard 4140, set it up and timed it as a five-shooter (this is a really small gun!)

This cylinder isn’t bored out yet, and obviously there is no breech-ring. To line-bore it I need a barrel. I considered making a .251 barrel liner for the gun’s existing .312 bore, but had concerns about rifling it. It needs to be an undersized smooth-bore initially so I can line-bore the cylinder, and then needs rifling. Trying to press a rifling-button through a lined bore seemed extra problematic; I could easily see shoving the liner out, or any number of other potential disasters. I finally decided to go a different route. I cut the existing barrel at the lug, Then bored out the remaining barrel to .430.

I grabbed some more 4140 and bored it through at 15/64″, then turned it down to size with a .430 stection to pass through the barrel-block. This was ultra-snug, so I slathered it with Red Loctite and press-fit it. Now I have a whole new barrel, and much less concern about rifling it.

This is the same length as the original barrel (3″.)  Now I hit a small snag; the 15/64″ drill is too short to bore the cylinder through the barrel. Oops… OK, a new 6″ Cobalt bit will be arriving Monday courtesy of Amazon. In the meantime I’m going to rig up a two-piece fixture from brass to clamp the cylinder and frame in the drill-press, and if I have the right stock on hand I’ll see about making a chamber-reamer for when the cylinder is bored through. To keep things simple I’ll probably do a hammer-mounted firing-pin. 

There is another issue- the trigger guard is really, really small. I’m considering cutting it away and making a spur-trigger, like a Pocket Remington. With the current trigger geometry it really shouldn’t be too difficult.  A little bress, a little silver solder and Bob’s Your Uncle (he isn’t really… we just tell people that to avoid awkward questions…) 

So progress is being made. One thing that has been suggested is that 5.7x28mm might be a better parent-case for this round than .22 Hornet. I’ll need to look into that. At this rate I might be shooting this before you know it!

Michael Tinker Pearce, 21 September 2019