This fired case is headstamped “W-W SUPER 25-06 REM”. The shoulder starts at 2.15" up the case, and has quite a sharp 50 degree taper angle (I’m not entirely sure which way tapers are measured, I mean 50 degrees from the start of the soulder to the neck, with the start of the shoulder being zero degrees. If I measured it with the case laying sideways it would be 40 degrees. To save confusion, the shoulder looks like the .300 Remington Ultramag. The inside neck diameter is usual for a .25-06. There is a ring in the case where the original shoulder would have been before it was fire formed. What is it?
I got a kick out of your attempts to describe the shoulder angle. :) :) You had just told me that you were studying to be an engineer and it seemed funny that you were struggling with an angle. But don’t feel bad. Measuring shoulder angles is not easy to do. When it comes to wildcats it is a critical measurement and is often the difference between two otherwise seemingly identical cartridges. I have made myself a template that helps me and I can usually come within one degree +/-.
Anyway, I think you have a 25 GIBBS. Rocky Gibbs was a shooter, gunsmith, wildcatter and experimenter in the 1950 and 1960s. He developed a complete line of “improved” cartridges based on the 30-06 case. (They can also be made from 25-06, 270W, 280W, etc) They all had very little body taper, a sharp shoulder, and short neck.
Gibbs himself used a 35 degree shoulder (70 degree included angle) although others who copied his cartridges used anything from 30 to 40 degrees.
Qual Cart has begun making some of the Gibbs cartridges with their own headstamp which makes them one of those semi-wildcats. But yours, in the WW Super case is a real wildcat.
Good find. Is this it???
OK how do you measure the angle on a wildcat? Vic
The same way you measure any angle. Everything you need to know you learned in the 5th grade. :) :)
Or you can use trigonometry. But i can barely spell it much less use it.
The photo below will let you measure a 30 degree shoulder. Take a sheet of paper and draw a whole bunch of intersecting lines just like those two, only make them 5 degrees, 10 degrees, 15 degrees, etc etc. Lay your cartridge on the vertical line and you will get within 5 degrees of the angle. You can interpolate other angles or draw more intersecting lines, say 2 degrees apart. Get the idea?? My template has all of the angles on one sheet but it’s a little more complicated than what most of you will need.
Ray: That makes sense even to me, thanks for the picture. Thanks Vic
Cheers Ray. You won’t believe how complicated my method of measuring a shoulder angle was…lets just say it involved a Boy Scout Troop some string and several Gin & Tonics ;)
Don’t throw out that gin and tonic. It will come in handy when you’re trying to measure something like a 38-40 WCF with an angle of 6 degrees 48 minutes and a length of only .153".
Also be wary of shoulder angle specifications that are expressed as an included angle. The military is famous for doing this. Why? I have no idea since the angle is the identical on both sides.
Ok Ray, what is an “included angle” in the sense that you used the term? I am a math and geometry dummy. Ranks right up there with my incompetence with computers! I am learning more on this Forum than I did thru the end of my 2-1/2 years of college!
Ray: Yas, that’s the one, thanks for the iD. Shown below is how I was attempting to measure the shoulder angle, plus the right way.
[quote=“JohnMoss”]Ok Ray, what is an “included angle” in the sense that you used the term? I am a math and geometry dummy. Ranks right up there with my incompetence with computers! I am learning more on this Forum than I did thru the end of my 2-1/2 years of college!
Don’t expect me to answer this where anyone can understand it. As I’ve often said on this Forum, I am but an ignorant farm boy, and I mean that literally.
Anyway, when two lines meet at a common point the angle between them is called the included angle. So, on a cartridge case if you extend lines from both shoulders until they meet at a point on the centerline of the cartridge, and then measure the angle between them it is the included angle. It’s twice what we ordinarily think of as the shoulder angle since both shoulders are the same.
Most military drawings that I have seen, and CIP and SAAMI drawings too, show the included angle. Look at the CIP print for a 30-06 and it shows the angle as 35 degrees. Most everyone else considers the shoulder angle to be 17 degrees, 30 minutes.
Maybe I’m wrong. Maybe every angle is an included angle and I am using the wrong terminology. There have to be Forum members who are much better at trignometry, or geometry, or whatever it’s called, and they should be able to explain it better.
One last thing before we move on to important stuff. Measuring shoulder angles with a template such as I described will get you close enough for all practical purposes. What many reamer makers use is an optical compartor, a very expensive piece of machinery that can measure such things precisely. I have found that you can make a homemade optical comparitor using a PC. Take a digital photo of your cartridge, put it into your photo-shop program, enlarge it (a lot), print it out and then measure from the printout.
Reamer makers, BTW, grind their reamers with CAD and CNC programs that take all the guesswork out. If they grind a 20 degree shoulder on a reamer it is most likely 20 degrees, 0 minutes, 0 seconds.
Ray - I think you did a dmaned good job of explaining it. Even a moron like me understood what you meant. If I am gathering right, measuring the “angle” of the shoulder is sort of like meauring the radius of a circle, while the “included angle” is more like measuring the diameter of a circle. So, naturally, the included angle will be exactly twice the “angle” (as we are using the term here! Right? I tnik I’ve got it. Like I said, I am not only learning cartridge stuff on this Forum, but also about history, and math and, thats to our friend in Florida, flora and fauna. That is NOT a complaint. What an interesting study this Forum is. I have always enjoyed the history of the cartridges and headstamps more than anything else to do with cartridges, except shooting them! All this ties in. If my Geometry teacher in High School had explained things like Ray does, I wouldn’t be so damned ignorant now!