An 'Artillery' Nambu and Lahti

[sheepherder]

In the first half of this thread, I pictured some of the steps in making my 'Artillery Nambu'. It turned out so well that I thought I'd see if I couldn't come up with a couple more 'fantasy artillery' handguns...preferably from the first half of the 20th century.

My second attempt is based on the Swedish M40 'Lahti'. Again I chose the Luger artillery rear sight paired with a modified M40 Lahti front sight. The Lahti uses the same pitch and diameter barrel thread as the Luger, but with a longer breech stub. This barrel is chambered in 9mm Parabellum.

(Please note - Not every step/operation is pictured. Oily hands, need to operate machinery, and not being able to mill/turn and shoot pics at same time preclude all operations being pictured).

Here is the first step in making of the 'artillery Lahti' barrel...



(1) I start with the 9mm barrel blank, about 9" - 10" long, 1 3/8" dia. This blank is from Green Mountain.

(2) Here I've turned both ends concentric to the bore and turned the breech stub down to .705" OD x ~.906" long. Entire blank was skim cut to make OD concentric with bore. 3-jaw lathe chuck, live center in tailstock.

(3) Threading the stub to 20tpi and turning the end for clearance in the Lahti receiver.

(4) Receiver is a nice snug fit on the thread. Receiver is a surplus Husqvarna M40 receiver I obtained from Numrich or Sarco some 20+ years ago. No serial, never used, as far as I could tell.

At this point it was necessary to mill the barrel top level with the receiver so that it could be removed for machining without losing the timing. I greased the threads, loosened & torqued it down 6 or 7 times, then milled a flat level with the receiver top. To do the torquing, I had to make up a special receiver wrench. The next series of pics shows -



(5) Thinning the excess metal where the taper will be.

(6) Rough cutting the 9mm Parabellum chamber - Finished, showing 9mm case in chamber. Brass piece shown in some pics is just a thread protector, internally threaded and trued to bore. Reamer is from Clymer, solid pilot finishing chambering reamer. High-sulphur content cutting oil from Ridgid, running lathe at lowest speed, feeding in 1/32" at a time; pulling out, blowing chips away, and re-oiling each time. I use a Clymer floating reamer holder in my lathe tailstock to feed reamer in.

(7) The special receiver wrench, made of 1" aluminum. Also shown are two special inserts for my lathe tool holder.

(8) Rough milling the rear sight base and barrel shoulder, using a rotary indexing head with attached 3-jaw chuck and tailstock.


The next set of pics shows more roughing out the sight bases -



(9) Ball milling the rear sight base; making it similar to the Luger rear sight base, using a 3/8" 4-flute ball end mill. In the past, I've cut partly-round sight bases in 4º increments; this time, I used 2º increments. Looks much nicer!

(10) Milling the barrel shoulder, still using the 3/8" 4-flute ball end mill.

(11) Milling out the dovetail section; 5/8" 4-flute end mill.

(12) Milling the dovetail for the Luger rear sight, 60º 4-flute dovetail cutter.

Next set of pics -



(13) Luger artillery sight fitted.

(14) Rough milling the front sight base & band.

(15) Turning down the rear sight base [front incline].

(16) Turning the taper. Following the lathe work, I doubled the spindle speed and progressively wet-sanded the tapered section with 220/320/400 grit wet or dry sandpaper. Not really polished, but smooths out the join where the two taper cuts meet.

The next step is milling the front sight base and barrel band.



(17) Milling the front sight band, using a 1/2" radius corner end mill, 2º at a time, 180º clockwise, 180º counter-clockwise.

(18) Finishing the band milling.

(19) Cutting the 1/8" slot that will become the front sight blade dovetail. I've decided I prefer the barrel band and front sight base as shown at http://www.gotavapen.se/gota/m40/pist40_4.htm and below -



I like the square band/blade as opposed to the stepped ramp.

(20) Cutting the 40º dovetail, using a Harvey 2-flute cutter.

That pretty much finishes the front sight blade dovetail. Next, I need to trim back the muzzle and face & crown it.



(21) Turning down the muzzle to same dia as end of taper.

(22) Excess barrel has been cut off and the muzzle faced & crowned. I'm using an internally tapered split barrel vise insert to hold the barrel in the lathe chuck.

(23) Barrel is 98% finished, minus a front sight blade.

(24) Installing the barrel in the receiver. Spirit levels used to index parts; squib rod in bore to eliminate any crushing from barrel vise; aluminum receiver wrench used to protect receiver finish.

Next will be fabrication of a front sight blade.



(25) Finished barrel and Luger rear sight mounted on my M40 Lahti, minus a front sight.

(26) Rought milling the new front sight blade, out of a piece of bar stock.

(27) Cutting the 40º dovetail, using a harvey 2-flute 3/16" dovetail cutter.

(28) Top of pic is the finished dovetail pressed into the barrel; bottom is the excess bar stock hacksawed off.

Next is milling the new front sight blade square.



(29) Blade has been milled square with base. I went with a simple 'Luger 1900' style base and band.

(30) Three shots of the blade being thinned.

(31) Milling the slope to the finished blade.

(32) The finished 'artillery' Lahti barrel mounted on my Husqvarna M40.

Some oblique views



(33) Just showing finished 'artillery' Lahti from different angles.

There are a couple of milling operations yet to be completed to the barrel; accelerator cut, extractor cut, and feed ramp cut. I need to remove the barrel for these operations, but since the main milling/turning is completed, and anything else will be hidden, I thought it was time for a photo shoot!

...And that concludes this exciting chapter of "Days Of My Lives"...