Like many of you, I like to take my vintage firearms to the range and experience what it’s like to fire these old warhorses. In order to keep vintage firearms in good working order, we sometimes must replace parts; either to keep fragile parts like firing pins from breaking or replacing worn-out parts to ensure the weapons function at the range. After I acquired my Papa Nambu pistol, it was clear from the get-go that my Papa Nambu needed a little TLC to keep her running in tip-top shape.
I bought my Papa Nambu about a year ago. It's all original right down to the springs, and that was the problem. The pistol itself is in well enough shape. Everything is tight, all the parts are serial numbered matching, and it came with the proper magazine, not a converted Type 14 Nambu magazine. However, as I worked the action, I noticed that the bolt wouldn't fully close unless I pulled the bolt fully rearward and released it. The bolt needed the full travel and force to completely lock in battery. I assumed this was probably a combination of worn-out springs and just being dirty. All things considered; she wasn’t in bad shape for a 100 plus year old gun.
I started with a complete tear down and disassembly of the pistol. I scrubbed and cleaned absolutely everything. I inspected all the parts and noticed that the firing pin spring had a few bends and kinks, and I felt that the mainspring had probably lost some of its "umph" over the last several decades. Worn springs are common in any military surplus firearm, and Japanese pistols are known to require new springs in order to function well. I added a thin layer of gun oil and reassembled. I left everything original for the time being.
Recently, I received a new spring kit from Wolff Gun Springs. Wolff makes gun springs for practically every gun ever made and is an amazing resource if you own military surplus firearms. I ordered the "Nambu 1914, 8mm Recoil Spring Pack". This spring kit only set me back $7.89 and only $12.70 after shipping! It's a great deal, and some piece of mind knowing your surplus rifles and pistols will function at their best. It’s always embarrassing to show off a neat and rare piece at the shooting range, only to have it run like crap.
After clearing the pistol, disassembly of the Nambu begins at the rear by turning the knurled striker guide 90 degrees to the left. The guide will then pop out under spring tension from the firing pin spring. The end of the original firing pin spring fits snugly over the tip of the guide, and both pieces come out together. The mainspring is removed by pulling the cocking handle past the rear of the bolt and unscrewing it counterclockwise. Be sure to keep a thumb over the front of the mainspring guide rod, or else it'll end up in orbit, or embedded in the wall. Once the cocking handle comes off, the guide rod can be removed from the front of the pistol.
As you can see in the photo below, my original firing pin spring has several kinks. The original spring measured 69mm in length and the new one was almost identical at 70mm. The new firing pin spring doesn't fit tightly over the end of the striker guide, so they won't go together as a unit during installation, but it doesn't affect the function at all.
Surprisingly, the new mainspring was shorter than the original. The original mainspring measured in at 137mm, and the new spring was 129mm. Installation is just disassembly in reverse order, and the pistol went back together with no issues. Once I had the Papa reassembled, I racked the bolt several times and felt that the new springs provided for a more positive lockup of the action, and the bolt would now fully close without pulling the cocking handle all the way to the rear. Other parts were replaced during this process, such as the firing pin. Firing pins on Japanese pistols are notorious for breaking, so I replaced mine with a repro shortly after buying the pistol. I dry fired a few times to see if there was any noticeable difference, and while there was no change in trigger pull or feel, it certainly feels like the firing pin strikes with much more authority than before. We'll see how everything performs next time I'm at the range.
Overall, I’m very pleased with this replacement spring kit by Wolff. I would encourage anybody who wants to preserve their vintage firearms, especially if you wish to actually shoot them, check out their selection at www.Gunsprings.com. The prices are great, shipping was only a few days, and now my Papa Nambu is running fresh springs.
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