Gonzo Long Barreled P08 Project

[sheepherder]

When I received my donor frame, a ~1939-era Mauser 'humpback', I test-fit my 1917 'cannon' assembly on it...It 'bound' in the rear frame 'ear' area. Measurements showed about .010" of squish-in. Maybe from being dropped, or some previous owner trying to 'accurize' it, or maybe just from the heat-treat during manufacture. I didn't want to try bending 70+ year old hardened steel, and .010" isn't all that much, so I decided to use progressively finer grits of lapping compound to take it down. Starting with very coarse valve grinding compound, finishing up with auto body polishing compound. Worked excellently!





Next up was to fabricate a 'lug' for the forearm I'll be installing. This will be somewhat like a Luger carbine forearm.



(39) Sawing the lug out of steel bar, milling all sides flat and parallel.
(40) Milling top flat and parallel.
(41) Milling bottom flat and parallel.
(42) Semi-finished lug.



(43) Rube Goldberg jig/fixture to hold lug in position for drilling & tapping frame.
(44) Center drilling the lug.
(45) Drilling for #4-40 screw.
(46) Tapping the drilled hole. This will hold the lug in position while being soldered.



(47) Lug has been positioned for silver-soldering.
(48) Lug has been silver-soldered in position, using Brownell's Silvalloy 355 and Wolverine Ultra Flux. This turned out to be a mistake. This solder has too high a melting point for a procedure like this, despite Brownell's claims/ads. I should have followed my instincts/experience and gone down to my local welding shop and bought some low-melting point brazing rod. It's been 30+ years since I've done any brazing/silver-soldering and I've forgotten most of What Works. This is on now, and I just hope it sticks.
(49) Milling off the attaching/positioning screw head.
(50) Re-drilling the takedown lever spring drift hole.

Next step will be to trim the excess solder and start fitting the wood for the forearm.

[sheepherder]

Most of the excess silver-solder has been filed/milled off, and now I want to check out how to fit the forearm wood. My woodworking skills are minimal, so I'm going to practice on at least one scrap piece of wood before I sacrifice a rifle stock for my forearm.



(51) Scrap piece of 2x4 soft Pine.
(52) Fully inletted and ready to trial fit.
(53) Not bad. A bit oversized, but acceptable.
(54) Closeup of inletted forearm with lug fitted.



Side view of mockup forearm, off and on. Doesn't look like much, does it? Took me about four hours to get it this far. Shame I didn't have a piece of nice Walnut instead of Pine, but them's the breaks. I'll have to mill out the rifle stock donor piece differently, since it won't be squared-off like this nice piece is. I have a couple old sawed-off buttstock pieces, rounded off, I'll have to think up a way to hold them in the vise for inletting.

Dug out a couple of old Walnut stocks from my 'parts box'. Top is 3/4 of an Ithaca Model 37 shotgun stock, bottom is [IIRC] a buttstock for the MAC-10, which I never owned but thought the stock might come in handy [Numrich of course]. I'm just squeezing the buttstock half between two plywood pieces in my vise...It seems to hold it OK. I'd rather I had a squared-off piece of hardwood, but for the little I need, this might work...maybe...



(55) Ithaca on top; MAC-10 on bottom. Mildewed, and Ithaca has a 3/4" hole drilled through it for the bolt.
(56) Fully 'inletted' with metal working end mills. I don't have any woodworking tools. I'm not a woodworker (as will become apparent).
(57) Inletted mockup placed on stripped frame/action. Profile needs to be taken down quite a bit and shaped, but this is just a practice forearm - the 3/4" bolt groove leaves too much gap on barrel sides. Other half of Ithaca buttstock will be Forearm Attempt #1...
(58) 1st Attempt at an actual Walnut forearm. Barrel channel and rear sight cavity have been milled out with a 5/8" ball end mill. This is the other half of the Ithace Model 37 shotgun buttstock, without the 3/4" bolt hole through it.



(59) Fully inletted forearm blank. Came out pretty good, although again, a lengthy tedious process.
(60) Top & side views; wood has yet to be pared down to desired profile. That comes next.
(61) Top view comparing Ithaca bolt hole (my barrel channel) with 1st Attempt barrel channel. The 1st Attempt is ~5/8" whereas the Ithaca bolt hole is ~3/4". Doesn't look like it, but it makes a big difference. I'll continue practicing on the 3/4" channel forearm blank for now.
(62) I've done a bit of mill-profiling on the 3/4" channel blank. Starting to look like a forearm.

My next step will be trying to figure out a way to hold the inletted forearm so that I can file/sand the squared edges. I'm thinking of an aluminum bar that fits tightly into the lug slot and extends beyond the ends. Have to check and see what I've got.

I found an old piece of 1/2" aluminum bar/plate and milled it to be a snug fit in the forearm inletting. Now I can clamp the inletted forearm in the vise for more milling, I'm working on the '1st Attempt' forearm here; the one with the tight 5/8" barrel channel.



(63) Using a 5/8" end mill to cut the 'Schnabel' curl. Also milling the taper on each side of the forearm.
(64) Milling the bottom of the forearm, up to the curl.
(65) Flipped over; scrap piece of aluminum & a shim in forearm, milling the top flat.
(66) Top view showing taper; side view showing profile.

Waiting for new end mills, cutters, and other miscellaneous tooling, so I'm switching over to the rear sight modifications.

[sheepherder]

I'm using the M24/30 FN Mauser carbine rear sight but I'm going to shorten the sight leaf. I found out the hard way that it is hardened. Anyway, after cleaning up pieces of broken end mills, I managed to use a Carbide end mill to mill the end and pivot slot of the sight leaf.



(67) Slot is already milled; milling end down.
(68) Shortened sight leaf on left; original sight assembly on right for comparison.
(69) This is why I hate micro-machining. I can barely see what I'm doing [which is milling .014" off each side of the pivot ears] and I can't get any feedback from the big heavy toolholder/vise/table feed. This is a 1/8" Carbide end mill.
(70) Another part I hate: Filing the square-cut ears round. My files are barely hard enough to cut the hardened sight leaf. Lots of filing and fitting; I want it to work, but also minimize the gaps. This ain't no work for an old man.

Next I need to cut the FN carbine sight ramp down to match the shortened sight leaf. This is a complicated procedure, involving calculating the bullet weight & shape, the powder charge and powder composition, the barrel length and rifling twist, bullet drop in meters, the curvature of the earth, local variations in gravity, Pythagorean theorem, Sine, Cosine, Tangents...Ah, screw it. I'm just going to make a flattened ramp.



(71) Milling down the back of the ramp to match the height of the barrel extension.
(72) The FN Mauser spring is way too strong for my taste; it's ~1/4" wide x .040" thick...so I dip into Brownell's flat spring assortment, the thinnest is .030", so I'll use that.
(73) The Brownell's flat spring stock is .500" wide, so I mill it down to ~.025". I clamped it to a piece of scrap aluminum.
(74) Finished spring shown next to FN Mauser spring. Next is to harden it.

I have other things going on at the same time as I work on this; some use different jigs/fixtures/vises, so I'll be jumping around on the machining...

I'm going to mill the front sight base down and cut the dovetail. I've clamped the barrel assembly between plywood boards to get a 'soft' clamp, and use a reinforcing rod in the bore just to be safe.



(75) Barrel/sight base is leveled and squared; ready to cut down.
(76) Sight base has been shortened/milled ~.250".
(77) 1/8" x .100" slot milled in center for dovetail.
(78) 40º dovetail cut into sight base, .100" deep. It is .197" wide at base.

I'll be making a sight blade for it next. I'm debating making it out of Delrin or steel...I may do both. The Delrin is quicker to make and can be slightly wider in the dovetail since it has some elasticity, which would make it easier to adjust and also stay fixed in position...

I've sawn a blank out of a piece of scrap steel. This will be the front sight blade.



(79) Milling the bottom of the steel blank.
(80) Milling the 40º dovetail.
(81) Sight blank has been pressed into the dovetail in the barrel. Now I am milling the sides flat and level with the front sight base.
(82) All four sides milled flat and level. I hate machining anything this fragile. One mistake trashes hours/days of work.



(83) Milling the sides of the sight to form a blade .120" wide. Using a radius end mill.
(84) Milling the sight blade at an angle to mimic the Finnish front sight blades used on Finnish Lugers and Lahtis.
(85) Mockup of barrel assembly and unfinished forearm. It looks odd.

[sheepherder]

Continuing work on the forearm. I made this one eight inches OAL. That makes it half the length of the barrel, which looks more balanced to me.

(34) Side milling the bottom of the forearm, using a 5/8" end mill and taking ~.030" deep cuts, ~.080" wide.
(35) Side milling the tapers on each side. Taking about 1/8" taper off. I thought I'd take a couple 'action' shots, just for a change.
(36) Milling the curved end of the brass inlay bar, with a 3/16" concave radius cutter.
(37) Drilling the relief holes for the inlay screws in the forearm inlay.



(38) Switching over to a 3/4" corner rounding end mill to round the bottom of the forearm. Another 'action' shot.
(39) Brass inlay being milled down with a 3/8" end mill to match forearm bottom surface .
(40) Beveling the upper edges of the forearm.
(41) Forearm, brass inlay, and brass attaching screws are finished. Wood has two coats of BLO on it, and I was surprised/disappointed to see how dark it turned out.



Next up is to stamp or cut index marks for the barrel/receiver and front sight ramp/base and barrel. I also want to bevel the muzzle and and crown the bore slightly.

(42) Here's a comparison of the 13" barrel & 6 1/2" forearm and the 16" barrel and 8" forearm. I've seen pictures online of 16" carbines with the short 6 1/2" forearms; they look disproportionate to me. These two combinations look much more proportional IMO.



Finishing up some of the 'little things' that need doing; feed ramp, extractor notch, muzzle crown, muzzle cap bevels...

(43) Using a curved lathe tool bit from Brownell's to cut a radius on the muzzle. I've had mixed success with this, it seems to chatter a lot.
(44) Cutting a 45º bevel on the end of the muzzle cap. I also opened up the hole a bit and beveled that as well.
(45) Cutting the feed ramp with a 10mm end mill.
(46) Different fixture; cutting the extractor notch with a 3/32" Woodruff keyway cutter followed by a 3/16" Woodruff keyway cutter. Sharp edges will be rounded off with a needle file.



That should pretty much finish up machining operation for the 16" barrel and forearm. I'll be looking for a mailing tube to send it off for blueing. I haven't decided if I should get a separate toggle assembly for this upper, or just use the 13" toggle assembly. Really doesn't matter, I suppose. I can only use one at a time. If I was to get a separate toggle assembly, I would probably be tempted to build another long-barrel frame assembly to go with it...

[sheepherder]

In another thread, Schutzenbob is building a Sharps-Borchardt with a forearm dovetailed to the barrel. That sounded interesting, as it would allow you to use a long barrel w/forearm on any Luger without the mounting lug for the forearm. I have one more Remington 700 30-06 barrel, so I'm going to make a long barrel with a forearm dovetailed to the barrel, somewhat like the Luger artillery rear sight dovetail. Long enough to hold two forearm attaching screws. And I'll make the inletting at the rear of the forearm wide enough to allow it to recoil over the frame.

Here's the start...

(1) Remington 700 barrel in 30-06 caliber.
(2) Turning down the breech end to the OD of the Luger barrel flange and then turning that down to the ID of my 1896 Swedish Mauser carbine rear sight. The two black spots are the OEM Remington rear sight tapped mounting holes. I'll be using them to attach my sight.
(3) Sight slipped on for final fitting.



The sight is from an 1896 Swedish Mauser carbine. I like the look of it, although like all Mauser sights, it is incredibly optimistic.

(4) The Swedish Mauser carbine sight, same ID as pretty much all Mauser sights.
(5) Threading the breech end of the 30-06 Remington 700 barrel to Luger specs.
(6) Cutting the breech stub to length, relieving the rearmost end of the thread.
(7) I've decided to make my barrel band/muzzle cap/front sight blade all out of one piece of steel. In the past, I've milled/turned the FS band out of steel rod and dovetailed the blade into it. This time I've drilled & tapped a piece of 1" key stock for the 1/2" x 28tpi barrel thread I'll be using, and the blade will be integral. At least, that is Plan A.



Next I'll be threading the barrel/muzzle for the muzzle cap/band/sight base, and milling the cap/band/sight to shape.

(8) These three pics show the muzzle being turned to diameter, threaded 1/2" x 28tpi, and the steel block from pic #7 above fitted to the barre.
(9) This is the steel block being milled in a rotary indexing head. I had the thought that milling it would be faster than band-sawing the block to the rough shape & size. I was wrong. It took much longer. Next time I do a similar part, I'll band saw it first.

First pic is the rough rounding of the block, second is the finished band, third is the muzzle of the cap sized to the same OD as the end of the barrel, before the threads.



Next will be milling the band flat on each side and then milling the blade.

(10) Milling the sides of the blade/base flat.
(11) Milling the top of the blade down to equal the height of the rear sight folded.
(12) Milling the blade itself down to ~.120".
(13) Muzzle cap/band/blade shown on barrel for effect.



I had to fabricate a new muzzle cap spanner; the pics are of it being milled out of 7/16" x 1 5/8" 6061-T6 aluminum bar. When it was done, I assembled the barrel, rear sight, barrel extension ['receiver'], and muzzle cap/band.

(14) Boring out the aluminum bar, milling a .350" slot, and test fitting the spanner and muzzle cap. Assembled unit shown for effect.



Next I will 'slope' the blade forward. I also need to mill the rear sight 'V' to a square Patridge style aperture.

[sheepherder]

More little stuff, milling the muzzle cap and the rear sight.

(15) Milling the ramp on the rear of the muzzle cap/band.
(16) Milling the 'slope' on the front sight blade.
(17) Milling the 'Patridge style' notch on the 1896 Swedish Mauser carbine rear sight leaf, folded section.
(18) Milling the 'Patridge style' notch on the slider.



Next on the list is to cut the extractor notch and the feed ramp.

But first, I'm itching to start on the forearm.

(19) Here I took time to make a much-desired modification to my receiver wrench - an extra locking lug recess in the handle. It came with the recess in the cap, but I level my Luger barrels using the front sight, so having the handle sticking straight up is awkward. Now I have 180º capability.
(20) Here's my piece of Walnut. My neighbor told me it is 'Black Walnut' and that is why it turns so dark with BLO. I dunno, I'm not a wood person...
(21) Here I've milled out the main channel for the barrel and rear sight base.
(22) I'm using a Woodruff key cutter to mill the slots for the frame rails. The barrel with forearm attached with recoil ~.3/8" over the frame. Right now, it all fits; I just have to lengthen the slots a bit.



I am finding it difficult to visualize the forearm in action and transfer the minds-eye image to the forearm. I had thought I would taper the barrel channel to match the barrel but the math was really confusing me. The masking tape in #21 shows what the OD should be at those points..

[sheepherder]

I got the first 16" barrel back from the bluer today. It's all together, and looks good!



Here's a comparison of the finished 13" and the finished 16". The 13" has the 6 1/2" forearm; the 16" has the 8" forearm. The 16" has the full length FN Mauser carbine rear sight; the 13" has the shortened FN Mauser carbine rear sight.



Work on the second 16" barrel with the Swedish Mauser sight continues.

[sheepherder]

Work on my second (or is it third???) 16" barrel continues. If you've read through page one and this page up to here, then this is all a repeat of what has gone before. I have done a few things differently, and I want to preserve them for future reference, so please bear along with me...

(23) Cutting the rear of the forearm. I've cut the 'scallops' so that they will recoil over the frame ~3/8". It makes the forearm wider, but the side profile will be similar.
(24) Now that the forearm has been fitted to the barrel and inletted to clear the frame, I need to locate where I will cut the dovetail for the forearm lug. To do that, I need to finish off the chamber and fasten the barrel to the receiver for the last time. Here I'm chambering it for 7.65 Parabellum.
(25) Cutting the feed ramp.
(26) Cutting the extractor notch. I use two Woodruff keyway cutters, and smooth the interior corners with a triangular file.



The barrel has now been screwed into the receiver and torqued to place the rear sight at exactly 12 o'clock relative to the extractor notch/feed ramp.

Next will be locating the screw holes in the forearm and then milling out a slot in the barrel for the dovetailed lug.

(27) Milling the slot for the brass inlay.
(28) Side-milling the bottom of the forearm; final cut.
(29 & 30) Milling a flat for the forearm attachment lug, and milling the ends for a 60º dovetail.



I'll make the lug next, with a 60º chamfer on each end for a ~2 1/8" long x 3/8" wide dovetailed lug.

(31) Milling the lug with a 60º cutter.
(32) Forearm lug drilled & tapped for attaching screws.
(33) Side milling the forearm taper.
(34) Milling the brass inlay for the forearm.



The barrel is completed. I'll fine sand the barrel itself to make it shinier. Rest of the remaining work will be on the forearm wood and the brass inlay.

Woodworking - I hate it. I hate sanding. So most of my woodworking will be done with metalworking tools.

(35) Using a corner-rounding end mill to round the bottom of the forearm.
(36) Using a tapered burr to relieve the top of the forearm.
(37) I'm rounding the tip of the forearm on my belt sander. I've left this to last because in the previous forearms, I've chipped the curl when milling the sides first. I had to make a wedge-shaped jig to hold the forearm square with the belt. Next, the part I hate - finish sanding the wood to minimize tool marks.
(38) This shot is to show the assembled barrel & forearm in battery and under recoil. You can see that the fixed forearm, with its carbine profile, recoils past the trigger guard. I had wondered if this would pinch the shooters trigger finger, but unless the shooter has fat sausage fingers, it doesn't hit the finger. In fact, I couldn't release the trigger quickly enough to even be close to the forearm tang.



That pretty much wraps it up for the fixed forearm and long barrel. The barrel will go out for bluing, and I'll put a couple coats of BLO on the forearm. The brass inlay also needs a couple thin cuts to make it level with the forearm.

Originally, I had worried that I would need to screw the dovetailed lug to the barrel so it wouldn't come loose. It has to be removable, as the rear sight needs to move past it on assembly. But while fitting the forearm wood to the barrel, I realized that the dovetail lug holds the forearm tight to the barrel and the sides of the forearm hold the dovetail lug from moving. It's a non-problem.

Here's a couple pics showing the completed barrel/forearm combination, with and without frame assembly.





I'll replace those pics with the 'finished' pics when the barrel comes back from being blued. Hopefully, I can take the pics outside.

[sheepherder]

Cleaning up some of the odd operations that remain.

(39) Milling the brass attachment inlay flush with the forearm. I'm actually milling it down to ~.004" from the surrounding wood. There is a .004" shim under the brass inlay.
(40) Heavy coat of BLO applied to the wood. Let soak in for 10 minutes, wipe off excess, and let dry. Another coat in an hour or so. Objects in foreground are the dovetailed steel lug, brass inlay, brass screws, and that .004" shim.



Here's two additional pics. I was trying to show how the fat barrel-mounted forearm is wider than the lug/frame mounted forearm.

This last 16" barrel and forearm was just an exercise. I don't expect it to win any beauty contests. I just wanted to see how it would look, and if it could mimic the profile/look of a 'traditional' carbine.

[sheepherder]

I got my faux 'carbine' barrel assembly back from the refinisher; it looks good!

Forearm is about as done as it's going to get. Everything has been assembled and function-tested, no problems.

To reiterate - The forearm mounts on the barrel and recoils over the frame. That makes it fatter than a 'real' carbine forearm, but the profile is similar. No modifications to Luger frame necessary.

Here's the finished product -

(41) Finished barrel assembly; blued, chambered for 7.65 Parabellum, notched, ramped, dovetailed, drilled & tapped. Swedish Mauser rifle rear sight, custom front. Original toggle mounted rear sight is lower than Mauser so it does not interfere with new sight picture. Swedish Mauser sight graduated to 1600 meters. It'd be like lobbing a baseball.



(42) Closeup of top & underside of forearm and installed dovetail lug, plus mounting screws. Like all Luger carbines, forearm must be removed to disassemble the pistol. The difference is that my forearms are screw-mounted instead of a tapered wedge.



(43) Closeups of Mauser sight up & down; front sight; and rear views showing hollowed-out wood.



(44) Static and cycled pic of faux assembly mounted on a 1937 Mauser Luger w/Erfurt toggle assembly. Side profile still resembles a 'real' Luger carbine but does not require any modifications to the frame for the forearm.



(45) View showing barrel & toggle train in full recoil. My finger is in no danger of being pinched. I'm 5'11" 195 lbs. If you had fat sausage fingers you might draw blood, but an average shooter won't get bitten.



That does it for my assortment of Gonzo long barrel Luger 'carbines'. Very interesting conversions and very informative to me as far as 'designing' and creating. This thread is too long and takes too long to load, so anything further will go into a new thread.

(Side view of dovetail lug added).