This is what I think is meant by included angle and throat. It desperately needs someone to draw a picture to go along with it.
Have I got this right?
Can you draw a picture?
Thanks;
joe brennan
This is what I think is meant by included angle and throat. It desperately needs someone to draw a picture to go along with it.
Have I got this right?
Can you draw a picture?
Thanks;
joe brennan
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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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When I was shooting the RCBS 165 sil bullet I suggested you start with I used to taper it til a slight mark was on the front of the forward driving band. That way I still had a strong band up front.
Remember I'm no artist so no smart a$$ remarks about the pictures. Just so you know, the curve in the bullet is a new design I'm working on for shooting around corners.
Pat
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Pat;
I think I understand this. I sent CC all the info, siomply .310” ball seat, 1 1/2 degree included angle taper. Etc.
Now, what I'm trying to do is write it all down for the BOOK!!! We're about ready to start selling CDs of the book, print to follow. Since it's never done, I added an ERRATA section on the site, and am putting all the new stuff there. So, if I can get someone to draw a nice picture, copying yours, I'll write it up and put it in ERRATA.
joe brennan
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Length per
.001”
Included
diameter
Angle
decrease
30 min
45 min
1 degree
1.5 degree
2 degrees
2.5 degrees
3 degrees
3.5 degrees
4 degrees
4.5 degrees
5 degrees
5.5 degrees
6 degrees
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Joe,
That'll be a nice addition to your book and hopefully help explain the throat business because I think it needs it. Now you have to add a 30-30 and 06 throat to finish the thing.
Pat
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Joe,
That'll be a nice addition to your book and hopefully help explain the throat business because I think it needs it. Now you have to add a 30-30 and 06 throat to finish the thing.
Pat Pat;
If you tell me what they look like, I'll try to draw them and add them.
I made the drawing as a graph in EXCEL, fiddled with the data table until it looked like your drawing. The rifling was just beyond me. I wish I knew how to use a drawing program, and had one.
joe brennan
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Here Joe. The only other one I know of is the Weatherby which is just a long lead (ball seat) like a cast bullet throat.
Pat
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Pat;
35-44 degrees, is it 35.44 degrees or 35 degrees 44 min.? 1-22 degrees, is it 1.22 or 1 degree 22 min? Is the 1-22 angle the throat?
Thanks;
joe brennan
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Joe,
The numbers are degrees and minutes. 1 degree 22 minutes and so on. The 1 degree 22 min. is the throat angle, 2deg 44 min. incl. No lead (ball seat). The 30-30 is 30 deg. incl. right from the end of the chamber neck.
Especially with the 30-30, but in all cases, I think you can see why I said before in another thread that the case neck has to be considered part of the throat
Pat
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Joe,
Your drawing in
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Since I'm the one who got the ball rolling on this there isn't a mistake. If you look at the chart it says length for .001 reduction at the top so for a 310 x 45 min. throat the tapered section would be 10 x .077 or .770 long. For a .309 x 45 min throat it'd be 9 x .077 and so on. I use the 45 min, 1 degree, and 1 1/2 degree so know they're right, although rounded off, and assume Joe figured the rest right although he'll probably add something to this.
I hate to do this but I don't think the little angled part of the throat less rifling is called the free bore. Free bore and ball seat are just different names for the same thing unless I'm wrong here but I don't think I am. Weatherby uses about a 3/8 inch long straight section they call freebore to keep pressures down but in actuality it's just a long ball seat.
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Wooooops, my mistake. I was talking about the 'free-bore diameter' pertaining to throat design, not the term concerning throat length associated to bullet jump. That is what Weatherby has, longer throats than the bullet AOL on a chambered cartridge. I've editied my other post to include the word diameter to free-bore.
The sketch is still wrong. I'm not talking about degrees or lengths, I'm talking about the sketch and Joe's dimension suggestion of a .310” diameter ball-seat, the ball-seat would be larger in diameter, not even with the grooves which would make the ball-seat .308” in diameter, even with the grooves. I don't know any chamber dimensions that have the ball-seat the same diameter as the groove diameter.
I'm not replying to argue, just replying to Joe's question if this is right and the sketch isn't. Trying ta help ya out Joe. :)
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Dan,
You lost me on most of what you're saying and maybe you could try again but believe me the sketch, prints, and more than likely all the numbers, are right. The only thing I see that could be wrong is adding a comma behind the word “diameters” in the part you quoted and possibly (but stretching) Joe not putting the lines representing the groove lower but that's no big deal and this isn't an art or blueprint reading forum. When talking about throats for all practical purposes free bore and ball seat are the same thing.
There's no argument here, just talking.
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Well Pat, I think we said our part. This is a forum so lets see what others have to say. I'm sure Joe's sketch is sufficient, but he's such a perfectionperfectpersonallanist......:D
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I have to read this stuff a long time. Here's what I think. The drawing is wrong, it needs the additions Dan shows to show that the ball seat is .310” and the groove diameter is .308” for example. My drawing just has one line pair showing the ball seat dimension and labeled the groove bottom.
I'll try to fix the drawing.
I do not understand the free bore/ball seat business.
joe b.
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Joe,
You don't need to call it anything, but when you correct the drawing there will be a tapered ring between the straight cylindrical ball seat and the throat's tapered lands. In your example of a .310” ball seat and a .300 bore with a 1.5 degree throat .3820” in length, the lands will .3056” in length and the 'free-bore diameter' length will be .0764".
An interesting point is: with your example given the land height or groove depth is .004” with a 1.5 degree angle, the angled land length will always be .3056” as you increase or decrease ball seat diameter. The free-bore diameter length is the only length that changes past .308". A .311” diameter ball seat would have the free-bore diameter length of .1719".....................Dan
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Here's the revised picture, I can't get my camera to take a white background picture.
??????
joe b.
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