Odd BBLs From Numrich

[m1903a3]

Since I have plenty of Navy lugers I measured a half dozen of my P.04s and came up with a 15mm diameter of the base band and 19.5mm from the bottom of the band to the top of the flat. Subtracting half the diameter (7.5) that makes it 12mm from centerline to the top of the flat. I measured my only lP08 and got the same result, which matches the lP08 drawing.

Putting my P.04s nose to nose with the lP08 confirms they have the same base height for the front sight.

Now for the interesting part: I have two P.08s. One is a mint 1918 Army P.08 and the other one is a rare Navy contract P.08 from the Navy's 1913 contract for 150 P.08 from DWM.

Both P.08s have the same 15mm band diameter as my lP08 and P.04s. However, they both are 17mm from the bottom of the band to the top of the flat. That translates to 9.5mm from the center to the top of the flat, not 10mm as shown on the print!!

[sheepherder]

Thanks Mike!

ARGH!!! I got the front sight band milled down to .630" dia rough cuts with the 3/8" end mill [shown below], and I can't find my 1/8" long flute end mill!!!

I had to order a new one. Take a couple days to get here.

[sheepherder]

If you look at the pic of the rotary indexing head in pic # 32 above, you'll notice little shims between the jaws and the M16 barrel stub I'm using as a mandrel. That's because the M16 barrel OD is not concentric with the bore. I have a small 3-jaw chuck that is centered on the indexing head, but that gets thrown all out of whack with an eccentric workpiece.

The stub was .012" off center. Trying to figure out how much shimming is needed at the two 'low' jaws to get it centered is a royal PITA. I spent an hour one night and another hour the next morning and finally got it within .002". I decided that was 'close enough'.

I just got in a small 4-jaw chuck for the indexing head (I have a 6" 4-jaw for the lathe) that will make this job much easier/quicker in the future. Lot easier when the other jaws aren't moving when you shim one of them.

[sheepherder]

Got the 4-jaw indexing head chuck mounted - works great! (Pic didn't turn out). Completed rotary milling the front sight band with 1/8" long end mill.

Faced off muzzle, cut crown. Mounted front sight band on barrel; mounted barrel on barrel extension ['receiver'] for pics. Also made up a special 'keyhole' spanner for mounting/removing the front sight band. Thread is 1/2" x 28tpi, same as M16/AR-15 barrel/flash hider.

Hard to photograph bright shiny objects in the shop.

[Olle]

Rich,

What kind of tool do you use for the crown? I have tried to grind HSS bits for crowning and other chamfering operations, but have never really been able to come up with anything that makes a clean, chatter free cut.

[sheepherder]

Originally Posted by Olle

Rich,

What kind of tool do you use for the crown? I have tried to grind HSS bits for crowning and other chamfering operations, but have never really been able to come up with anything that makes a clean, chatter free cut.

Brownell's sells a curved lathe tool bit that isn't too bad for a curved tube end. I have 30º/45º/60º 'chamfering cutters' [countersinks] that I use to break the sharp bore edge and blend in the lands & grooves. (I also have tried them for cutting feed ramps; they work pretty well for that too). I'm pretty slack on 'rounding off' the end of thin barrels. The flat squared-off end looks pretty nice to me.

Edit: I just realized which barrel this is. Since it has a threaded-on front sight base, it's not rounded at all. I left it 'squared' and just broke the sharp bore edges with a 45º chamfering tool.

[Olle]

Originally Posted by sheepherder

Brownell's sells a curved lathe tool bit that isn't too bad for a curved tube end. I have 30º/45º/60º 'chamfering cutters' [countersinks] that I use to break the sharp bore edge and blend in the lands & grooves. (I also have tried them for cutting feed ramps; they work pretty well for that too). I'm pretty slack on 'rounding off' the end of thin barrels. The flat squared-off end looks pretty nice to me.

Edit: I just realized which barrel this is. Since it has a threaded-on front sight base, it's not rounded at all. I left it 'squared' and just broke the sharp bore edges with a 45º chamfering tool.

I looked at Brownell's cutter, and the complex grinding explains why I haven't been able to make one... I haven't had much luck with countersinks of any kind, they just shatter at any RPM. My only salvation is a crowning tool set (also from Brownells), but I would like to come up with something that works in the lathe... I hate to buy tools I can make, so I might try and grind a short miniature boring bar before I cave in and order the cutter.