Included angle and throat-is this right?

Joe,

 I can't open an Excel file on this computer so can you change your attachment to something else?

 Don't get all goofy with this throat business. All you're doing is running a reamer in that has a straight section with an angle on the front to go from whatever size straight section you chose, .310 if you decided to go that route, down to bore size. The reamer makers and smiths usually know what they're doing and if you order a .310 x 1 1/2 degree throat reamer that's what you'll end up with usually. 

 A close approximation of taper length to every .001 diameter reduction would be .038 for a 1 1/2 degree, .057 for 1 degree, and .077 for 45 minute, all angles are included. In other words if you were going to use a .310 x 1 1/2 degree incl. throater and assuming you had a .300 bore the tapered part of the finished throat would be .380 long, .010 x .038 equals .380 in length. I've throated barrels using all three tapers depending on bullet length.

 If using the above mentioned .310 x 1 1/2 minute throat you'd have a tapered section sans rifling about .076 long and then a .304 long taper with progressively stronger rifling as you approached bore diameter, or .300.

I'm no artist but DREW a fast picture to give you something to look at. Don't know if it makes things clear or not but if not ask. There's also a picture of a bullet and what tapering will do and how it'll make the bullet fit. Remember, the throat will have rifling for .304 of it's length so if the nose diameter of the bullet was .302 and the body .3095 you'd have .076 contact at the front and .057 on the first band if you tapered the bullet so the most forward edge of the bore ride was .300.

I don't know all of what bumping a bullet does but from some I've measured I think it primarily expands the nose so there's more contact with the taper to provide guidance. I use LBT designs or something I cut myself along the same design exclusively so don't feel the need to bump, two ways of getting the same result. They bump up I squeeze down.

All that aside if you're real question is how much information do you have to send CC about cutting your throat just tell him you want a .310 x 1 1/2 degree incl. throat to fit the dummy round you sent him. If he doesn't understand what you're talking about find someone else to do it. If you're concerned about it maybe a phone call and a letter will ease your mind.

Pat 

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