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.401 BOBCAT by Lee Martin The .401 Bobcat was designed in April of 1994 and was more of a response to the downturn in .41 Magnum popularity. For some time I had collected the .41’s only to see them be delegated to the role of a second tier chambering. The forty caliber on the other hand gained tremendous acceptance in the early 1990’s and much of this stemmed from the advent of the 10mm Auto and .40 S&W. Though both are fine cartridges, personally I’m not fond of autoloaders. With the increased availability and selection of 10mm jacketed bullets and cast moulds, it only seemed logical to devise a forty caliber better suited for a revolver. Though the .38-40 Winchester works just fine as a pistol round it lacked the performance that I was after. Enter the .401 Bobcat. Magnumized 10mm’s were nothing new to the world of handguns. Pop Eimer devised a potent middle bore round in the 1920’s that was based on the .401 Winchester Self Load case cut to 1.25". The .401 Boser was another cartridge of similar power that was developed in the 1940’s. Commercial offerings never became a widespread reality, though Herter’s did manufacture their infamous .401 Powermag in the 1960’s. All of the aforementioned provide impressive ballistics and easily would have served as an excellent 10mm revolver round. The limiting factor though was the availability of brass. Both the .401 Powermag and .401 Self-Load are obscure and when offered tend to be very expensive. In light of this I searched for a more common round as the starting point for my 10mm wildcat. A quick review of case dimensions yielded the .220 Swift as a suitable parent case. The "Who", "How", and "On-What" on the project was simple. My father, though a full time physician, had for years done gunsmithing as a hobby (I should note that he builds guns only for personal use and has never attempted to make a business of it). Most of his work dealt with home built bench rest actions and custom rifles on the Mauser 98. Other talents include Thompson Center Contender barrels and XP-100 conversions. By the early 1990’s though he began to devote more time to Ruger Blackhawk’s and soon began manufacturing his own cylinders from round bar stock. Some of his early conversions included the .38-40, .44-40, .25-20, .32-20, and .30 Streaker. The cost of these projects is lessened by the fact that he makes his own chambering reamers as well as reloading dies. In-house heat treating also provides for another level of self-sufficiency. Originally I wanted the .401 Bobcat to be 1.40" in overall length and inside case reamed so heavy 10mm bullets could be used. My father had already built a .38-40 Winchester on a Ruger Blackhawk though and due to the amount of barrel protrusion in that gun, a long cylinder could not be employed. As a result, we settled on the standard 1.29" configuration. I quickly purchased a like-new Blackhawk in .357 Magnum and a few pieces of 10mm barrel blank. Reamers and form dies were made within a couple of days and cylinders were roughed out in a similar amount of time. Case forming simply entailed cutting the Swift brass slightly oversized and expanding the necks to accept the 10mm slug. Inside case reaming was necessary and was performed as to allow for the use of heavy bullets. The last step is to trim the round to length. What was almost overlooked on the cylinders was the ratchet height. Most our previous conversions involved rounds that had a rim thickness of about 0.060" whereas the Swift case has a thinner profile at 0.049"; because of this standard length firing pins wouldn’t indent the primer enough to cause ignition. The workaround involved machining Bobcat cylinders to have a ratchet height of 0.011" less than that of a standard Ruger. Finalized cylinders were unfluted and subsequently heat-treated to Rockwell 40 and blued. The first two pistols were completed in July of 1994. My Blackhawk was a blued convertible (the other cylinder was a .38-40) while my father’s made use of a 6.5" tube. Initial testing was done with a 180 grain Hornady XTP bullet that was propelled by a full case of H110 or W296. Recoil was manageable and both guns proved extremely accurate. The second bullet that was tested was a 265 grain cast .403" slug that was sized to .401". Ironically, we had the mould lying around for years and I believe it to be originally designed for the .40-60 Winchester cartridge. This combination shot very well even in a barrel with a 1-18 twist. Recoil was definitely heavier but still not unpleasant to shoot. As pleased as I was with the .401 Bobcat, I still wanted the round to be 1.40" in overall length. In the summer of 2001 my father and I lengthened the case by 0.11" and again used the Ruger frame as a starting point. This time though I opted for the Super Blackhawk configuration in stainless (I’ve always had an affinity for the Dragoon style backstrap). The cylinder was manufactured from 416 stainless stock and was sized to make use of the entire frame window. Barrel selection was a little more of a question mark. Historically, we’ve made use of either Shilen or Douglas barreling for our conversions, but neither offered 10mm in stainless. As a result I settled on Pac Nor and was satisfied with not only the barrel they shipped but the service they provided. The longer Bobcat holds roughly 4-6 grains more of H110/W296 than its 1.29" counterpart. Though we have yet to chronograph the round, I would estimate a velocity gain of 150-200 fps over the shorter version. I have no doubt that the 1.40" Bobcat can exceed .41 Magnum performance by a similar margin, yet again this will need to be confirmed through chronograph testing. Trial loads did reveal that case pressure is significant, especially with the 265 grain bullet. Some of my early combinations with the 265 actually expanded primer pockets, even on a case a strong as the .220 Swift (obviously our loads were reduced slightly to eliminate ruined brass). I should note that other faster powders such as Unique have been tried with the heavy bullet. The result though is an increased recoil profile and a suspected drop in velocity. As with most magnum revolver rounds, H110 and W296 seem to be the optimal propellants. My father and I have worked with many different cartridges in the Ruger Blackhawk over the past twelve years. Some include our .458 Devastator (a .458" on 1.4" belted magnum brass), the .357 Bain & Davis, .454 Casull, .500 Linebaugh, .375 Atomic (.375 SuperMags cut to 1.4" – not to be mistaken with the .357 Atomic of the 1950’s), and the .30 Streaker. Of all of these, I tend to favor the .401’s. In my opinion they offer excellent power, a reasonable level of recoil, and extremely flat trajectory. I certainly hope to publish chronograph data once testing is complete.
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