Manurhin MR73 project

Manurhin is a French firearms manufacturer probably best known for their PP and PPKs manufactured after the war under license from Walther. However, they are also known for designing and manufacturing what some people say is the worlds finest combat revolver- the MR73. Here is an excerpt from the Wikipedia entry:

The MR73 was standard issue with France's Gendarmerie and in some police units including Special Weapons and Tactics teams (RAID, GIGN and comparable units).
The GIGN selected the MR73 in part for its ability to almost indefinitely withstand 150 rounds of full-power ammunition during daily range practice. These teams also use MR73's with scopes and 8" and 10" barrels for tactical purposes. Over one million rounds were allegedly fired through one example.

Every MR73 is match grade accurate, shipped with its own factory test target fired at 25 meters. Averaging 15 rounds, no group over 20mm (0.8 inch) diameter with selected ammunition is allowed.
The MR73 has an adjustable trigger weight in both double-action and single-action modes- a feature not found in any other revolver. These adjustments do not alter the strength of the main spring, ensuring reliable primer ignition. This is due to the use of roller bearings in the trigger mechanism along with extensive hand fitting and polishing of components during assembly. The MR73 requires more than 12 hours of hand-fitting at the factory, making it about 50% more expensive than competing U.S.-manufactured brands.
The revolver can be converted to 9mm Parabellum with a supplied replacement cylinder.
Cylinder chambers are finished with an impact process that makes them glass-smooth and extremely hard. The factory proof-fires each cylinder chamber with .357 Magnum ammunition generating 30% more pressure than the C.I.P. maximum allowable pressure for the Magnum cartridge. The factory guarantees that the cylinder will not burst or show any bulging or deformation with .357 Magnum ammunition developing double the standard maximum allowable pressure of 300 MPa, meaning the cylinder can withstand 600 MPa (92,800 psi, or 46.4 tons per square inch).
The frame, cylinder, and barrel of the MR73 are made from ordnance-certified, alloyed steel. Barrels are manufactured by cold-hammering. The rifling is formed during the forging process, eliminating the need to cut the rifling as a separate manufacturing step. This creates an extremely hard and microscopically smooth internal barrel surface.

I have always wanted to find one, but they are so rare in the US the prices were astronomical. Luckily, CAI was able to import a bunch of police surplus and the cost was reasonable. Although well used, the example I got is extremely accurate- if a little loose in the lockup and endshake departments.  The grip is very comfortable but absolutely ugly- also much too large for concealed carry.

After taking the sideplate off and examining the inner workings, I came away impressed. Manurhin's goal was to improve on Smith and Wesson's K frame, and in some respects they succeeded. It is more complicated, and difficult to manufacture- but the geometry leads to a shorter, heavier cocking action with a smoother trigger at a comparable weight of pull. A lot of this has to do with the rebound slide running on bearings and the adjustable main and trigger springs.

You can see in this picture how the original straw coloring of the trigger and hammer have faded. After going through it and cleaning it up, hammering then filing out any random dings and cold bluing the resulting bare spots- I decided to make myself a set of grips. Woodcraft provided the block of Osage Orange:

I then cut it into slabs and began inletting the backside to fit the frame. You can see that I JB welded some washers to the back to key into the cutout in the frame.

 It took quite a bit of rasping and sanding, but I ended up with exactly what I was looking for. I trimmed down a stainless screw and added a brass insert for the grip screw. Afterwards it was 4 coats of Tung oil with 2 days of drying between each coat. The Osage Orange was a pleasure to work with, it held together well during routing and sanded smooth. It has a lot of oils in it and some consider it the American equivalent of Teak.

 

The last shot is a before and after, you can see the new grips are much lower profile. The next step was to bend out a slight kink in the trigger guard then work on re-straw coloring the hammer and trigger. I attempted to color them in the oven, but I found a propane torch worked better in the end. I heated the parts up until they began to turn yellowish, then quenched in water. There is a finesse to this as the larger surface areas need more heat and vice versa- once the color change stars, it comes on quick and doesn't stop until quenched. The colors go from light yellow to straw to bronze to purple to dark blue to light blue . You want to make sure the pieces are quenched to keep them hard (and arrest the color change) as opposed to letting them cool naturally which may anneal them. I'm not a metallurgist, but I don't think the temperatures involved require re-tempering. Here is the end result:

 

 

I may have a try at rebluing this revolver eventually, but in the meantime- I will enjoy carrying and shooting it. It is tremendously accurate and I enjoy the work that went in to it as well as the history behind it.