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sheepherder · 04-28-2014, 02:54 PM

I was asked if I was planning on making any more 'artillery Nambu' barrels. No, I am not. This was a 'design exercise', and I made it in 7.65mm Parabellum caliber because I like that caliber and it is similar enough to the 8mm Nambu dimensionally and ballistically to make tailoring my handloads fairly easy.

The 9mm artillery Luger barrel could easily be adapted to a modified Nambu barrel extension, with the same dimensional adaptability as the 7.65. It would be relatively easy if you had access to an engine lathe to turn down the Luger barrel thread, re-thread it, and re-chamber it; and a milling machine, to re-cut the extractor notch and feed ramp. A chambering reamer would be required too, in most cases.

The Nambu barrel extension would need to have the old barrel cut off, face the cut, and drill, thread, and relieve the extension. This can all be done in a lathe.

The advantage of the artillery Luger barrel is its thick shoulder. This allows for indexing the front & rear sights to the Nambu extension without cutting into the barrel taper.

A 'standard' Luger barrel, in 7.65mm or 9mm, could be adapted to the Nambu extension, but more care would be needed because of the narrow [relative to the artillery) shoulder. The 4 3/4" pencil-profile Luger barrel is a dead ringer for the OEM 8mm Nambu barrel. It would look almost original.

I made my 'artillery Nambu' barrel with the 1900-style barrel band and Lahti-style front sight blade because I like their looks. The Luger front sight is actually more like the OEM Nambu.

I would select the 9/16" x 24 NEF thread size for the Luger-to-Nambu barrel stub and extension. The Nambu bolt is ~.702" dia and the OD of the extension is ~.862". 9/16" would give an extension wall thickness of ~.150". If the Luger thread of ~18mm x 20 were used, the wall thickness of the Nambu receiver would only be ~.077". That's kind of thin to me. I wouldn't go up to 5/8" thread because that would not leave me much of the original breechace for the bolt to bear against.

Below is an additional pic showing the OEM Nambu two-section feed ramp and bolt face compared to the 'artillery Nambu' feed ramp.

04-28-2014, 02:54 PM	#17
sheepherder Lifer Lifetime Forum Patron Join Date: Feb 2009 Location: ...on the 'ol Erie Canal... Posts: 8,181 Thanks: 1,398 Thanked 4,438 Times in 2,327 Posts	More Notes I was asked if I was planning on making any more 'artillery Nambu' barrels. No, I am not. This was a 'design exercise', and I made it in 7.65mm Parabellum caliber because I like that caliber and it is similar enough to the 8mm Nambu dimensionally and ballistically to make tailoring my handloads fairly easy. The 9mm artillery Luger barrel could easily be adapted to a modified Nambu barrel extension, with the same dimensional adaptability as the 7.65. It would be relatively easy if you had access to an engine lathe to turn down the Luger barrel thread, re-thread it, and re-chamber it; and a milling machine, to re-cut the extractor notch and feed ramp. A chambering reamer would be required too, in most cases. The Nambu barrel extension would need to have the old barrel cut off, face the cut, and drill, thread, and relieve the extension. This can all be done in a lathe. The advantage of the artillery Luger barrel is its thick shoulder. This allows for indexing the front & rear sights to the Nambu extension without cutting into the barrel taper. A 'standard' Luger barrel, in 7.65mm or 9mm, could be adapted to the Nambu extension, but more care would be needed because of the narrow [relative to the artillery) shoulder. The 4 3/4" pencil-profile Luger barrel is a dead ringer for the OEM 8mm Nambu barrel. It would look almost original. I made my 'artillery Nambu' barrel with the 1900-style barrel band and Lahti-style front sight blade because I like their looks. The Luger front sight is actually more like the OEM Nambu. I would select the 9/16" x 24 NEF thread size for the Luger-to-Nambu barrel stub and extension. The Nambu bolt is ~.702" dia and the OD of the extension is ~.862". 9/16" would give an extension wall thickness of ~.150". If the Luger thread of ~18mm x 20 were used, the wall thickness of the Nambu receiver would only be ~.077". That's kind of thin to me. I wouldn't go up to 5/8" thread because that would not leave me much of the original breechace for the bolt to bear against. Below is an additional pic showing the OEM Nambu two-section feed ramp and bolt face compared to the 'artillery Nambu' feed ramp. Attached Thumbnails __________________ I like my coffee the way I like my women... ...Cold and bitter... Last edited by sheepherder; 04-29-2014 at 08:09 AM.