.251 TCR stands for 'Tinker Centerfire Rimmed.' It's a straight-walled .25 caliber case designed specifically for revolvers, and it's a passion-project of mine.
Back during the .22 shortages a fellow known on the forums as Magnumwheelman had a single-six made in .25 ACP, sort of as a re-loadable .22 LR replacement, and it worked out pretty well. In fact I planned doing my own conversion in .25 ACP, but I got to thinking, and that's where the trouble began. The tiny ACP has a very limited case capacity and a relatively weak head, so there are limits on how much you can hot-rod it. What if I did a rimmed cartridge, made of stouter stuff and with more case capacity? Ideally it could be loaded anywhere from indoor gallery rounds to somewhat hotter than .22 Magnum.
Magnumwheelman was on board right away, and sent me some .22 Hornet brass as a parent cartridge, then later sold me some leftover .251 barrel from TJ's. I got some .25 ACP dies and was off and running.
I started with the sizing/de-priming die. I made a replacement for the de-priming pin, a .250 hardened-steel rod with a well-rounded point on the bottom end. Using a .22 Hornet shell holder I ran the .22 Hornet into the die and squeezed it in over the pin to form a straight-walled case. I had to take off the bulge at the rim of course; quickly and easily done with a fine file and a hand-drill. chuck the case up in the hand drill, spin it and apply the file... easy-peasy. then I shortened the case to the desired length.
The brass has an outside diameter of .275″ and is .980″ long. The rim diameter is approximately .350″.
Naturally I needed a gun to test-fire it from. I had picked up an Uberti 1873 Black Powder cheap; this is a percussion version of the Single Action Army, mainly made for countries where owning cartridge firearms is problematic. I had to change the breech and firing pin. I bored the cylinder through and press-fit 4140 rod in to fill the chambers. I bored out the barrel and inserted the .251 liner, a press fit with Loctite Red. I'd wanted to leave the barrel at 4-5/8", but had some issues with tools that required me to cut it to 3-1/2". I line-bored new chambers, then reamed the and chambered them with a .275 reamer for the new cartridge. Works a treat. I slab-sided the barrel to give it a distinctive look.
Now that I had a test gun it was time to start reloading and get the chronograph out. I swaged some 38gr LSWCs, and bought some PPU 50gr FMC. I also picked up a tin of H&N Grizzly 31gr. LHPs and a couple hundred 35gr. Gold Dot JHPs. I loaded some of the LSWCs over Unique, and got about the energy of a hot .22 LR from a 4" barrel. I branched out to Power Pistol and Red Dot, with excellent results from these latter two powders. Then I discovered Rimrock Bullets Hard-cast 55gr. LRNFPs and grabbed 500 of those. I've done a lot of experimenting and have been giving my new Chronograph a workout.
So far I've developed gallery loads with about 5 ft./lbs. of energy all the way up to loads giving around 170 ft./lbs. from my 3-1/2" test gun; the cartridge is proving every bit as versatile as I had hoped.
I've even put together a second project gun- an 1849 Wells Fargo (reproduction) cartridge conversion in .251.
(No, the sheathed spur trigger is not a feature of the original gun.)
Anyway, I'm having a ball playing around with this and thought I'd stop lurking and start sharing.