Delightful diversion loading the 8mm Nambu Guns Magazine, Magazine, August, 2002 by Charles E. Petty •
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Νεξτ During the years following World War II, we saw a flood of military surplus handguns either brought home as war trophies or imported as surplus. Lugers, P-38s and Nambus were plentiful. I well remember when you could buy a Luger for $25, a P-38 for $15, and a Nambu for even less. German pistols were popular because they fired readily available ammunition. But the Japanese 8mm Nambu cartridge might as well have been made of unobtainium. Ammunition was truly scarce, so Nambus didn't gain much popularity among shooters. And, at the time, few collected Nambus. Several Nambu variations exist, but the model most commonly seen is the Type 14 Nambu. This is the only one I'll talk about here. The 8mm Nambu cartridge looks, at first glance, very much like the .30 Mauser, except the case is just a little too big. The bullet would be, in the American scheme, a true .32 caliber with a diameter of .320 inch. Of course American .32s are really .31s (.311 to .312), and of absolutely no help with this project. Cooking From Scratch One of the great assets of handloading is the ability to shoot guns for which factory ammunition is either unavailable or too expensive. Nambu ammunition has never been loaded in this country by the large ammunition companies, but it was one of the foundations atop which Midway U.S.A. was built. By modifying cartridge cases such as the .30 Remington, and later offering brass manufactured especially for Nambus, Midway made it possible to shoot the Nambu, as well as a few other exotic cartridges. When Midway U.S.A discontinued Nambu ammo, the market was left to a few custom reloaders -- frequently using Midway's brass. Today that ammo has become a collector's item, and the brass has sold for as much as $1 a piece. Later we saw the arrival of 8mm Nambu brass from Bertram in Australia, and loaded ammo from The Old Western Scrounger, which is a wonderful source of odd ammo.
Surprisingly Nice Pistol Maybe interest in the Nambu stems from nostalgia over World War II, or because the Nambu has been discovered as a very interesting pistol in terms of both design and collectability. It is a simple striker fired, locked breech autoloader. They are actually a pretty ingenious design, and much better than we've been led to believe. The frame is made from a single large forging and the barrel and receiver are a single piece of steel. While most barrels screw into the receiver, the barrel of the Nambu is just a solid extension. It must have been a bear to make. If you study one in good condition, it's easy to see the degree of skill that went into its manufacture. Whatever the reason, interest in Nambus is growing. Maybe it's just that the thing is really fun to shoot, which is how I got hooked. My buddy had one at the range and let me shoot a couple of rounds of the old Midway ammo. And that's all it took. My search began with a review of a couple of catalogs, and a passing comment on an Internet board I frequent. Within minutes someone replied, directing me to Huntington Die Specialties as a source for bullets. My call to them was perfectly timed, for they were just ready to announce the availability of Nambu brass made exclusively for them by Starline. Components Readily Available One of the hassles of loading metric cartridges is that everybody seems to have their own idea of exactly what 8mm really is. Usually it falls somewhere between .318 to .323 inch. The Nambu sits right in the middle, and bullets of true .32 caliber are just right. Huntington offers a plated .320 inch diameter 107 grain bullet, and I was also able to locate some 102 grain .321 inch diameter cast bullets at Liberty Shooting Supplies. None of the major bullet makers offer jacketed bullets that proved useful. So even though you won't be able to find these components everywhere, they are not hard to get. A quick check showed that RCBS and Redding offer dies on a special order basis. But in the commonly available manuals, one thing you won't find is loading data. Some old books show data using Bullseye, 231 and Unique. As a matter of curiosity, I broke down a round of original ammo for measurements. Loaded with 4.4 grains of a greenish flake type powder, the 102 grain FMJ bullet has a diameter of .320 inch. References show this load as having a velocity of 1,066 fps. Setting The Baseline Reference ammo is not exactly plentiful, but a few rounds of the scarce Midway ammo were fired and chronographed at 1,039 fps. Also, I had five rounds of original ammo. Only one of them fired, but it delivered 1,030 fps. The agreement between the two is wonderful, and based on those measurements, a target velocity of 1,000 fps was established. I was very much working in the dark, for I had no pressure test equipment for the Nambu
cartridge. Even though the pistol is a locked breech design, it is not a candidate for hotrodding. If I'm going to err, I'm going to err on the side of conservatism. In looking for data, all I could find was located in two cartridge conversion books that explain how to make brass from another case. And both of those showed loads at around 900 fps. Later I received an e-mail with some suggested starting loads using Bullseye, WW 231 and Unique with a 102 grain FMJ bullet. No pressures or velocities were available but it served as a reference. Initial loading was done in Huntington's brass using their plated 107 grain bullet and CCI small pistol primers. Overall length was set to duplicate the Midway ammo at 1.25 inches. Loading was done with increasing charges in small increments until velocities duplicated the factory loads. As this work was going on, I learned of a source for a 102 grain cast bullet and ordered some from Liberty Shooting supplies. I then repeated the load workup using them. The test pistol was a Type 14 manufactured in 1942. The reloads worked perfectly in the pistol and even the lightest loads functioned just fine. Even though loads duplicating the factory ammo appeared to be perfectly safe, accuracy was much better with lighter loads. I quickly concluded that it really isn't necessary to exceed 1,000 fps. Nambus have a reputation for good accuracy. Considering that the barrel doesn't tilt, it should shoot well. Indeed they do, although neither of the two pistols I tried shot as well with the jacketed bullets as they did with the cast. The cast bullets loaded to 900 to 950 fps routinely delivered groups of 2 inches or less at 25 yards. But the plated bullets sometimes shot patterns instead of groups. Given these results, with the plated bullets I gradually worked down in velocity. Best accuracy was achieved with a load of 3.6 grains of 231, which produced about 850 fps and consistently shot groups hovering around 3 inches with two different pistols. That load functioned perfectly in both guns and has become something of a standard for me. The real significance of this story is that we are once again able to shoot an interesting and historically significant pistol without enduring a great deal of hassle. Everything we need is available from one or more sources. But several words of caution are in order. We are dealing with old guns with unknown histories. It pays to examine them very carefully before shooting them. If there is any doubt, have the gun inspected and approved by a competent gunsmith. Firing pins are fragile looking and I'd avoid dry firing them. Also, it might not be a bad idea to replace the dual recoil springs. Fortunately W.C. Wolff offers them. It's funny how a chance event can direct us. Had my buddy not let me shoot his Nambu and had I not called Huntington to ask about bullets, I probably wouldn't own a Nambu today. And I'd be missing the fun of shooting it. Go figure. LOADS WITH HUNTINGTON'S 107 GRAIN PLATED BULLET Charge
Velocity
Bullseye start
maximum
3.0 3.3 3.7 4.1
850 898 981 1,040
4.0 4.2 4.4
986 1,011 1,041
W-W 231 start maximum Unique start
4.0 996 4.2 1,004 maximum 4.4 1,041 LOADS WITH LIBERTY'S 102 GRAIN CAST BULLET Charge
Velocity
Bullseye start maximum
3.0 3.3 3.5
952 974 1,034
3.5 3.7 4.0
942 971 1,071
3.5 3.7 4.0
934 997 1,066
W-W 231 start maximum Unique Start maximum
FOR MORE INFORMATION CONTACT: Huntington Die Specialties [530] 534-1210 www. huntingtons.com Old Western Scrounger [800] UPS-AMMO www.ows-ammunition.com Liberty Shooting Supplies
P.O. Box 357 Hillsboro, OR 97123 phone: [503] 640-5518 W.C. Wolff Co. [800] 545-0077 www.gunsprings.com
