The 10x25mmR /.40 S&W Ruger Convertible Revolver Project

[Outpost75]

Last year I started a thread and discussed the concept.



Rather than trying to revive an old thread from the archives, I'm starting a new one here to bring everyone up to date. My buddy Mike and I got our two revolvers back from John Taylor. Our First range trials were with the .40 S&W cylinder, because we wanted to use that cartridge to establish a baseline for comparison with our wildcat. Firing ordinary 180-grain FMJ I shot a couple test groups, and made sight adjustments before firing handloads with the Accurate 40-182H bullet, which, incidentally is the same profile as our 40-220H, simply truncating the nose to increase the meplat size and to reduce the weight.

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Hand held off sandbags while running over the chronograph I'll take these!

I have test rounds loaded with 180FMJ, 182 LFN and 220 LFN all with 5 grains of Bullseye to shoot in the 10x25R cylinder as soon as our range road is repaired from the recent storm washout.

DougGuy made our dies by cutting down and honing out .38-40 dies on a Sunnen hone. RCBS dies are "harder than woodpecker lips" and go through stones like crazy, Lee dies also work and aren't quite as hard, but still eat up stones. So his firm cost to do a set of these is $150, if you supply the dies. Doug buys the stones, does the work and returns your dies insured in small flat rate box.

If you want a Lee Quik-Trim case holder shortened, that's a bit extra.

The die mods needed are as follows, and much less expensive than having custom dies purpose built.

1) FL sizer and seater are both cut off by 0.4"
2) A new thread relief is turned on each die.
3) Neck of the sizer die is honed inside up to .420".
4) Neck of the seater die is honed to .429"
5) Ball seat of the seater die is honed to .402", if too tight so that it needs to be.

If you want to cut down .44 Special cases, Doug can take a .44 Special case holder for the Lee Quik-Trim, cutting 0.16" off the top, then you adjust the Quik-Trim to cut your necked down .44 Special brass to 1.000+0.000/-0.005"

A much simpler way to make cases in quantity is to buy Starline .44 Russian cases, neck them down and just use them that way. The .44 Russian brass comes from Starline 0.0960-0.965" long. After necking down to .40 they are 0.970-0.975". This is a wee bit short for the chamber length on the Manson reamer, which is 0.955" ahead of the rim seat, plus rim thickness, but causes no problem whatever. The dies as modified by DougGuy are purposefully made a wee bit short so that you have wiggle room to adjust sizing, etc. to get an exact fit to your revolver chamber.

We elected NOT to get an inside neck reaming die made to thin the case necks, which saves both money and effort. We are using the necked down Starline brass as-is. With our Manson reamer as originally ground per print .400" diameter jacketed bullets fit correctly in the .424" diameter chamber neck, using necked down .44 Russian brass, which are about 0.001" thinner than cut-down Starline .44 Special.

There was NOT enough clearance using cut-down .44 Specials or if loading cast bullets of .401" diameter or larger. So, we got Dave Manson to make and send to John Taylor a separate .429" neck reamer to enlarge the chamber necks in our cylinders provide 0.005" additional clearance, which in practice works VERY well. If anyone else wants to order the 10x25R (aka .40/.44 Spl.- Short 1-Inch) reamer from Manson I recommended to him that the neck diameter on any future .40/.44 Special reamers should be increased to .428-.429".

(Anybody wanting a copy of the chamber print PM me, I couldn't figure out how to attach the .pdf here...)

I am using 5 grains of Bullseye as my basic load in the 10x25R with either 182 or 220-grain lead bullets.

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As FYI 20 grains of Goex 3Fg or 4 grains of Trail Boss comes up just to the shoulder. You could compress 24 grains of black with a drop tube or compression die.

When everybody in our group gets done with having revolvers made, the next step is to have Dave regrind the current reamer to provide die reamer, and the order a new reamer to do a rifle chamber. A .401 or .4015 chucking reamer can be used to rough a revolver cylinder and the rifle reamer with appropriate pilot used to finish the revolver chamber. New reamer will increase neck diameter to .429" to provide needed release clearance and will have two pilots, one .392 to fit lands of Green Mountain 10mm barrel blank and the other .400" to fit throats of revolver cylinder.

Then we are having some Bond Arms Derringer barrels in .40 S&W rechambered, perhaps having a couple lever-action cowboy rifles short-stroked and rebarreled, and maybe even a rook rifle or two...

What we wanted was a rimmed revolver cartridge which could match .38-40, or 10mm Auto performance without excessive powder space, being produced easily using a common case for feedstock and for which .40 S&W full-charge or 10mm Auto starting data could be used as a safe starting point.

It has promise as a black powder cowboy cartridge, too!

[lar45]

Looks like an excellent little cartridge
Did you start with a 357 / 9mm convertible, or get new cylinders made?

[Outpost75]

Looks like an excellent little cartridge
Did you start with a 357 / 9mm convertible, or get new cylinders made?

We both started with New Model Blackhawk .357/9mm convertibles and had the cylinders rechambered, used a Green Mountain "gunsmith special" 10mm barrel blank and had the revolvers rebarreled to match the factory contour, finished at 5", with the original front sights and ejector rod housings remounted.

Dave Manson made the revolver chamber reamers in both 10x25mm and .40 S&W having .402" cylinder throats and a long enough cylindrical section to clean up the Ruger cylinders. Because our plan was for several folks in our group to do multiple guns with multiple cylinders, both reamers were TiCN coated so they would stay sharp and hold size. John Taylor produced a fixture just for boring our group of Ruger cylinders, and is set up to do this precisely and efficiently.

[3leggedturtle]

That’s cool looking round, sorta like miniature 577/450 Martini!

[Outpost75]

That’s cool looking round, sorta like miniature 577/450 Martini!

Yeah, I was thinking more of the Morris Tube subcaliber for the British 6-pounder, but you understand.

As FYI black powder capacity is 20-21 grains of Goex 3Fg or 4.2-4.5 grains of Trail Boss for 700 fps with Accurate 40-182H from 5" revolver or 650 fps with Accurate 40-220H, sort of a 2/3 scale .455 Webley. With smokeless 5 grains of Bullseye is a nice power level with either bullet.

Here are pics of test groups from the 10x25mm cylinder:

Attachment 221707Attachment 221708

[Outpost75]

I decided to order another mold from Tom at Accurate which would give me a blunt, heavy, ogival wadcutter bullet with large meplat, which was visually distinctive from 40-220H, so that I could tell the lower velocity, close-range "thumper" loads at a glance from the heavier, high-velocity smashers.

The result is 40-224H, which is based loosely on Tom's 39-205D bullet for the .41 Long Colt, truncating the nose back to .405" length to as to enlarge the meplat to 0.3", increasing driving band diameters to .402" and the bore-riding nose to 0.400" with nose tolerance negative, so that bullets drop freely into revolver chambers, but are well aligned in transitioning the long cylinder throats into the barrel. I added a 0.3" bevel base to compensate for the nose shortening to bump the weight back up to approximate the 40-220H, and to ease loading. Seating depth is only about 0.3" so that there is minimal intrusion into the powder space.

The .405" nose is too long for .38-40 Colt SAAs or typical 10mm autopistols, but is perfect for Ruger single-actions in the 10mm or .40 S&W. Initial load plan is to work up sort of a .40 cal. version of the .38 Super Police or .455 Webley Manstopper type load about 700 fps, starting initially with 3 grains of Bullseye in the .40 S&W revolver and 3.5 grains in the 10x25mm, necked down .44 Russian case, and go from there.

When the mold arrives in a few weeks I will be looking for a few beta testers with 10mm revolvers to test sample bullets and to report their results back here. If you have one of the new Ruger 10mm/.40 S&W convertible revolvers, or one of the Charter Arms or Taurus .40 S&W snubbies, PM me if you'd like bullets to test when I have received the mold from Tom and have had time to cast a bunch.

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