Disclaimer: I am not a craftsman or an artisan; I'm not a gunsmith or master machinist. I'm just a blue-collar gun hack. My work is crude and minimalist; no frills, no polish, nothing to be especially proud of. I don't have the years or thousands of dollars to wait for a master craftsman to make me what I want. So, I do it myself. It's not beautiful, but as the bard says, "Beauty is in the eye of the beholder". I can look at 50 feet of railroad track and think it's beautiful. Like National Lampoon has proclaimed: "Creosote is King!" 
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This is the latest in my series of Gonzo long barreled military handguns. The previous two being based on the profile, dimensions, and rear sight of the LP-08 'Artillery' Luger pistol. This one is actually based on the P08 Luger, but the barrel will be longer than the 'artillery' model, and the rear sight selection is still undecided.
This particular project was inspired by a 'prototype' 7.63 C96 Mauser-chambered conversion done by Herbert Werle some time back and sold on Hermann-Historica. It uses a shortened 7.65 caliber Mauser rifle barrel with OEM front and rear rifle sights, adapted to the Luger frame, and re-chambered. I kind of liked the idea, but the sights are a bit too big for me, and I'm not fond of stepped barrels.
Here's two pics of Werle's excellent conversion -
I'm going to emulate his idea, but slightly different.
First pic is of some of the available parts I have on hand.
Two barrels are Remington 700 30-06 cal barrels; one is a Winchester 30-06 Mod 70. The resulting long barrel Luger will be chambered in 7.65 Parabellum [30 Luger]. The top [Winchester] barrel has already been fitted with several rear sight assemblies. The top pic has an 1891 Argentine Mauser carbine rear sight fitted. The front sight and band is from the 1891 Mauser carbine as well. Shown below that barrel is an FN M24/30 Mauser carbine rear sight, a Luger artillery rear sight with two different dovetail mounts, and a Martini Cadet rear sight.
The [Winchester] barrel shown with the 1891 Carbine sights mounted has already been chambered for 7.65 Parabellum and threaded to fit the Luger P-08 receiver pictured.
Next pic is of the above mentioned barrel with the 1891 carbine rear sight mounted [top] and the FN rear sight [below]
Both will fit (22mm barrel) as will the dovetail mount in the pic above this one. At this point, I am leaning toward the 1891 Carbine sight but the FN Carbine sight is more attractive and quite similar to the Luger Artillery rear sight in construction. I'm considering shortening both the sight leaf and the mount and utilizing that sight.
The four pics consolidated below show the first stages of the barrel machining.
(1) Barrel segment is approximately 13" long, and has been turned to 19.5mm [.768"] dia for the rear sight band and the breech stub is being turned/threaded to ~.709" dia/20tpi thread.
(2) Breech being faced off and clearance cut for receiver, length of .740".
(3) Beginning cutting the 7.65 Parabellum chamber. Clymer reamer, 1/32" cuts, lots of high-Sulphur content cutting oil, back out & blow chips off every 1/32" cut.
(4) Chamber rough finish cut. Chamber will be hand cut for headspace after torquing to the receiver.
Edit: Numrich has a listing for the base for my Martini 310 Cadet rear sight [shown below on a base]. I ordered one, and if it works, I'm thinking of using that rather than the Mauser/Luger tangent sights. It's both elevation and drift adjustable.