Gonzo Long Barreled P08 Project

[sheepherder]

I now find that I need to make a keyhole spanner to torque my front sight base on & off with...Using 5/8" aluminum plate, hole bored to ~.640" and a ~.290" slot...



(27) Hole was drilled to 1/2", slot milled, and hole bored out to ~5/8"+.
(28) Closeup of front sight base in keyhole spanner.
(29) Torquing the front sight base to the barrel with the keyhole spanner. Spirit levels used to align the two.
(30) Spanner removed; checking level again with level on top flat of front sight base.

Next up is facing off the muzzle and crowning.




(31) Muzzle face has been turned in lathe, slight chamfer cut on edge of muzzle, crown being cut.
(32) Barrel has been torqued on receiver/barrel extension; rear sight located, holes drilled for #4-40 screws, front sight base torqued on, hole drilled for #4-40 setscrew and being tapped in this pic.
(33) Angle plate has been mounted on mill table at 58º; barrel has been removed from receiver/barrel extension and leveled in barrel vise clamp; bolted perpendicular to table in preparation of milling extractor notch.
(34) Making first extractor cut with .093" Woodruff keyseat cutter.



(35) Second extractor cut with .200" Woodruff keyseat cutter.
(36) Cutting feed ramp with 10mm end mill. Barrel held in barrel vise clamps which are in turn held in angle vise set at 50º. My thanks to Gerry Tomek for his sleuth work in determining the correct angle!
(37) Just a closeup of the finished ramp cut.
(38) Torquing the receiver on the barrel again, to check extractor clearance in receiver/barrel extension.

I've received a donor frame, I'll be prepping that for a forearm lug soon. Couple other things need doing on the barrel, plus the rear sight leaf needs shortening. Always something.

Interlude

Off-topic, but worth relating...I was milling an aluminum block square earlier in the week, idly watching the end mill spin around in the spindle and the feed table move slowly along, keeping an occasional eye on the TV on the shelf above me, when the air compressor in the corner suddenly kicked in...It took about half a second for me to lunge forward and disengage the feed before the circuit breaker cut power to the 3in1 mill...The 3in1 has two 8.8A motors, one for the mill spindle and the other for the lathe/table feed...The compressor motor is 15A...All plugged into a 12/2 w/gnd wired circuit with a 20A breaker...

So today I ran 10/2 w/gnd to the 3in1 with a 30A breaker and moved the compressor to a 20A breaker. I usually know enough to run the compressor and build up a reserve and switch it off before running the 3in1, but this time I forgot. If the power cuts off while I'm cutting with the feed on, it can be disastrous to the workpiece and expensive to replace the broken cutter. Better to be safe now than sorry later.

Here's the finished breech - Extractor notch cut; feed ramp milled; barrel torqued in place.

[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]

To all interested members who have wondered if this project has died, it has not. It is temporarily on hold until such time as finances and interest resume.

A member of the other forum approached me about a project that ended in a major disaster some years ago. He wanted a 9mm Walther P1 barrel liner removed and a 30 Luger stepped liner installed. I did a test barrel and it worked out very well. I then did two more and managed to burn out a set of HSS drill bits and a reamer. I upgraded to Cobalt and the next one turned out quite acceptable. I've done several more. Still waiting for a review.

[sheepherder]

...Sometimes, it just won't work...

I thought it would be neat to make my P-08 rear toggle knobs 'dished', like the M1900 toggle knobs. So, I took measurements from side-on and top-on photos and figured out that the 'dishes' were cut 10º from the vertical axis. I also figured that to give me a straight-in cut with my end mill, I need to angle my mill vise 16 1/2º from the horizontal axis. My vise is adjustable, so that took care of the 16 1/2º, and I made up a fixture to hold the toggle at the required 10º [Pic below].

I had previously test-fit various shot glasses, jelly jars, lids for whatever I had that used lids, and determined the diameter of the M1900 dish to be 50mm/~2". My biggest end mill is 1 1/2", used to mill off flash on AR-15 lower receivers. Anything bigger would run several hundreds of dollars, which I wasn't eager to spend for 'dishes'. The 1 1/2" end mill would have to do.

When I got it all completed and set up, it didn't look right. After many years of machining, I have a rough eye for what I am doing. This wasn't right.

It turns out the M1900 toggle/knobs are .150" wider than the P-08 knobs. That threw my straight-in measurement off. I'd need to increase my angle. But then the dish wouldn't be right - the cutter is too small for the narrower knobs. The dish wouldn't look right.

I could mill the dish flat, instead of concave. But that's not right either.

In the end, I shelved the 'toggle dishing project' due to lack of tooling. A few days wasted making the fixture and taking measurements.

Sometimes you eat the bear...Sometimes the bear eats you...

[sheepherder]

First pic -

While pawing through my tool collection I noticed I had a 1 1/2" carbide tipped dovetail cutter left over from some obscure one-time project...So I decided to have another go at dishing the toggle knobs...

The toggle chosen is one left over from some other project <sigh>. I clamped my 'fixture' in my mill vise and 'bored' the toggle dishes. Time consuming and fairly apprehensive, as I had visions of carbide inserts flying around the shop...

But it turned out OK, machining-wise. Still the wrong diameter, and leaving enough metal for the rail contact surface didn't allow much to be machined off, but at least the concept is proven.

I guess that the bear and I are about even on this one.

Second pic -

I was contacted by a forum member who was interested in a 'dished' toggle, so I ordered a carbide shell end mill cutter plus arbor. It should be in shortly.

The 2 1/2" Carbide fluted shell end mill came in; I finished my 'prototype' P08 dished toggle...

Very slow milling; 10º angle from horizontal; plunge milled. I retained the ~.156" contact patch for the frame ramp. The arc of the scallop is not as great as an M1900 due to the M1900 being .150" wider in the knob area.

Came out OK; there were a few tool marks but sanding with 220 wet-or-dry wrapped around a suitable mandrel took them out pretty quick.

Visually not as impressive as the wider M1900 toggle, but it's different...