Originally Posted By: 2-piper
Chuck;
All I can tell you is "Do The Math". Any chamber cut with a cone angle of 5 per side is going to be a short one. It will not be a "Modern Long Cone", period. In my 35+ years in the machine shop I have cut enough angles & tapers to know how to calculate them.
I Double & Triple checked my trig, it is correct.
If you take the 1907 drawing Drew posted with the included taper of 1 7/8" per 12". Do the trig on this taper & you get 4 17' & 21 angle" per side. Calculating the length of cone for the .069" difference in chamber & bore diameters gives a length of .460".
Double checking by another means that .069" is 3.68% of 1.875.
3.68% times 12.5 = .460"
With that same .069" difference between chamber & bore a 5 angle per side would give a cone length of .394", certainly not a long cone.
Remember SAAMI is suggested Not Law.

Miller
All I can tell you is the Clymer and Manson reamer makers products and the SAAMI drawings match the 5* angle in 12, 20, 28, and 410. Even the "new" 3 1/2" 12ga has a SAAMI spec of 5*. But 1988 could be called ancient now. Call them what you will, modern or not. It's fact. If you order a catalog reamer it comes with a 5* cone unless custom specified at greater cost and longer lead time. I have three examples that I ordered off the shelf in this century and they are still 5*. The gun makers themselves along with ammunition makers developed these standards, a.k.a. "Industry standard". They haven't changed since you said they aren't modern. Perhaps there's another way to marginalize these facts?

Last edited by Chuck H; 11/07/15 06:36 AM.