Measuring Chamber Casts?

[Blackfly]

I've done a couple chamber casts over the years. I'm pretty satisfied with measuring case head, rim dimensions and case neck diameters. Most of what I've done have been pretty straight cases. I've been following the recent thread on the modified chamber, and realized that I don't have a clue on how to measure the shoulder angle, or correctly measure shoulder diameter. I would appreciate some advice from some of our more learned members.
Thanks
Bfly

[sharps4590]

Black, I don't know how one would go about measuring the shoulder angle, I never have. I suspect there is some type of tool out there to do so but don't know. The shoulder diameter I picked up from looking where the drawings in my books showed where the measurement was taken. Basically, just below where the bottom of the shoulder angle enters the case body. With a sharp shoulder angle it's pretty easy. Some of those old slope shouldered cases can be a bit annoying.

[mike ford]

Blackfly,
I suggest you make a photocopy of the chambercast(centered on the paper), and extend the lines with a straightedge and pencil. Then it should be pretty easy to measure the angle with a protractor.You won't be able to get it to the second, but can be pretty close, if you take care.
Mike

[Greg47]

You can make a scale drawing, using the dimensions from the casting. Make a centerline and take shoulder dia measurements in a couple places as well as the start. Then its easy to measure the angle with a compass. Assume you use cerosafe? Greg

[Peter K]

Now you did it, Mike. Another thing to try with chamber casts. I tried my scanner with the cast parallel and with the cast perpendicular to the light bar. The edge of the cast is not clearly shown in both cases due to the shadow along each edge. I then tried photographing the casting placed on a white background with and without flash. The same shadow problem arose. I then photographed the casting placed on a dark non reflective background. This latter method without flash worked best and gave a useable picture off which a shoulder angle could be measured. While the shoulder angle could be determined I would not rely on this method to reproduce correct diameters as there may be some enlargement/reduction in the process. How do you do it?

[Greg47]

The old fashioned way. Measure it, plot it and draw the lines. Then it will be right.
Greg

[mike ford]

Of course, Greg is correct, but most people either don't have the necessary tools or desire to make the precision measurements for this, and if they could, they could calculate the angle.Most people have or can obtain cheaply a protractor. Due to differing diameters, the shadows won't be the same, but will be fairly consistent and there should still be a line to work to. In any case, the actual cartridge dimensions will not match the chambercast(chamber)dimensions,they are usually .003-.005" smaller. If they were the same, the cartridge wouldn't chamber. In all the years I have been doing this, I never felt the need to measure the shoulder angle( the difference between a normal and improved chamber is pretty obvious). I have struggled with shoulder diameters, however. I just took several measurements, as carefully as I could and took the mean.
Mike

[Blackfly]

I knew that folks who deal with the myriad of German cartridges would have sorted out some options.
Thanks for the help.
Bfly