Alternative Artillery Barrel Fabrication

[sheepherder]

Originally Posted by TennBill2

Anxious to see how you finish reaming with the receiver on. I'm about at the same point, don't really want to spend $40 or so for a one off. Upside down 3/8 extension too big.

Then here we go!!!

First pic, we have the stripped toggle train installed with a dummy round in chamber. This is a 7.65 Luger round run through my RCBS die set (without expander). This is the ammunition I'll be shooting, so this is my baseline. I'm measuring the gap between the breechblock and the receiver.



I remove the dummy round and measure the gap again. (I have a rod inserted in the barrel to press toggle train back against the axle & take out any 'slack').



Removing the receiver, taking care not to crush the barrel.



Measuring the amount of the dummy round protruding from the chamber. I know it's too much because in the first pic the toggle is not fully closed.



I've figured out that I need to extend the chamber another .028" to give me .004" headspace (my target). .046" minus .022" is .024"...Add my target of .004" and I need to remove .028" to get my target headspace.



After reaming, I get .074"...This means I need to extend another .002" to hit my target of .004" headspace...



I'll re-install the receiver and hand ream the last .002"...



Here's that turned-down 6" 3/8" drive extension...



For all practical purposes, I'm done...But it's always good to double-check, so I've put my stripped toggle train back in place with the dummy cartridge, and put a 'headspace shim' between the breechblock face and the dummy cartridge...a .004" shim fits, and the breechblock remains closed and my .022" feeler is nice & snug...and .006" worth of shims gives me a loose feeler and a slightly raised toggle... finally, .005" worth of shims feels just right...

(My 'headspace shims' are just circles that I've punched out of plastic shim stock).



.005" is close enough to my target of .004". I'm easy.

There's dozens of ways to do what I just did, this is just one that I chose. YMMV

(Note: Any mistakes in math or spelling are my screwup. It's hard to machine, do math, and take pics at the same time)

Edit: BTW, I've done the headspacing now because I'll be machining the front sight blade in place, and the barrel won't fit into the headstock after that)...

[Neil Young]

Fantastic work--I believe that 90% of a machinist's skill is displayed by the machining sequence concept and the setup. This is of course more evident as the task complexity increases. You obviously have a high level of these skills. Anyone can learn to do a repetitive machining job on an assembly line, but the true measure of a craftsman is displayed on those one-of projects that are seldom, if ever repeated. Great job.!

Neil--an amature hobby machinist

[sheepherder]

The battery on my digi-cam pooped out while I was machining the front sight blade blank, so just imagine a small square of steel being milled & dovetailed...

And then pressed in the barrel dovetail...And then milling the sight assembly sides flat...



Front and rear sides milled flat...



Front sight squared off...



Milling the blade itself...Using a corner rounding end mill, just for S&G...



Front sight is roughed to shape; need to mount rear sight to determine blade height and finalize profile (it will be like the Finnish Luger profile...sorta)...



Hmmm...I'm running out of Allowed Images in my albums...I'll have to verbally describe what I'm doing from now on...)