Included angle and throat-is this right?

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  • Last Post 04 December 2007
CB posted this 14 August 2007

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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CB posted this 14 August 2007

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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CB posted this 14 August 2007

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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CB posted this 16 August 2007

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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CB posted this 16 August 2007

HERE'S ANOTHER TRY:

 

CHAMBER THROATS-THE INCLUDED ANGLE

            The “ball seat” is the cylindrical section of the throat. For a 30 caliber rifle with .300” bore and .308” groove diameters, the ball seat might be .310".

 

Length per

 

.001”

Included

diameter

Angle

decrease

30 min

0.115

45 min

0.077

1 degree

0.057

1.5 degree

0.038

2 degrees

0.029

2.5 degrees

0.023

3 degrees

0.019

3.5 degrees

0.016

4 degrees

0.014

4.5 degrees

0.013

5 degrees

0.011

5.5 degrees

0.010

6 degrees

0.010 The “included angle” is twice the angle shown in the drawing. Thus, if the angle shown is 1 degree, the included angle is two degrees. The throat shown tapers from the ball seat to the bore diameter. For the 30 caliber rifle mentioned above, the throat would taper from .310” to .300".

The length of the tapered throat is determined by the included angle of the taper. If the included angle in the rifle mentioned above is  1.5 degrees, and if the throat is to taper from .310” to .300", a diameter decrease of .010"; then the length of the tapered throat is .380", see the table. (10 X .038” = .380") And, another example, a 2 degree included angle throat would be 10 X .0029” = .290” long. And so on.

 

 

 

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CB posted this 16 August 2007

I guess the picture and the rest just don't work here.

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CB posted this 16 August 2007

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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CB posted this 17 August 2007

pat i. wrote: 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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CB posted this 17 August 2007

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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CB posted this 17 August 2007

The other.

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CB posted this 18 August 2007

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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CB posted this 18 August 2007

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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CB posted this 14 November 2007

Joe Brennan wrote: CHAMBER THROATS-THE INCLUDED ANGLE

            The “ball seat” is the cylindrical section of the throat. For a 30 caliber rifle with .300” bore and .308” groove diameters, the ball seat might be .310".  

Joe,

Your drawing in http://www.castbulletassoc.org/attachment.php?id=546>CHAMBER THROATS-THE INCLUDED ANGLE.doc is missing the 'free-bore' diameter area, with your example of a .300” bore, .308” groove with a might be .310” ball-seat. The ball-seat would be .002” over groove diameter. That .002” angled part of the throat between the cylindrical ball-seat and the angled groove and lands is called the 'free-bore' diameter. Thus, the greater the diameter of the ball-seat over groove diameter, the greater of area the free-bore diameter. The red lines here in http://www.castbulletassoc.org/attachment.php?id=546>CHAMBER THROATS-THE INCLUDED ANGLE.doc II is where the bottom of the groove ought to be.  The two arrows point to the free-bore diameter section.  Good example tho Joe...........................Dan

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CB posted this 14 November 2007

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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CB posted this 14 November 2007

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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CB posted this 14 November 2007

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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CB posted this 14 November 2007

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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CB posted this 19 November 2007

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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CB posted this 19 November 2007

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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CB posted this 19 November 2007

Here's the revised picture, I can't get my camera to take a white background picture.

??????

 

joe b.

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CB posted this 19 November 2007

Dan,

You're wrong but I give up.

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CB posted this 20 November 2007

Hey Joe, that looks good, even in color.  I'll try one later and see what a scaled one looks like......................Dan

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CB posted this 20 November 2007

Hey Joe, see if this works for you. It as close I can gan git to scale. Its a .310” dia ball seat about .120” long with a 1.5 degree throat........Dan

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CB posted this 20 November 2007

This is certainly a better picture than I can make. I make the drawing in EXCEL, copy it to WORD, print it, photograph the print, put it into PHOTOSTUDIO, add the text andthen insert into a WORD document. Along the way I get lost several times, and I can't photograph the WORD print so it comes out looking white. There must be a better way.

I put the picture up on cast boolits in the middle of a thread about terminology, and the argument began.

I think it's time to put the words and meanings, and many words have several meanings, down into a simple paper.

From the end of the cartridge case place to the bore and groove place there are any number of things that can be cut into the ?chamber?.

How about we tell what the words mean to us? Remember, there's no right or wrong, if “XXXX” means “AAAA” to you, that's just what we want. Let's give the newcomer, and me, some help.

Here are some of the words:

Throat

Ball Seat

Leade

Free Bore

Bore Diameter

Groove Diameter

?????????

joe b.

  

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CB posted this 20 November 2007

Alight, this is my take on the definitions as I have been taught from the likes of Tom Gray and George Morrison...

Throat - the section of the barrel that begins at the point where the rifling starts

Ball Seat is the same as free bore.

Free Bore - the portion of the barrel from the end of the chamber to the beginning of the throat that is free from any rifling.

Bore diameter - the diameter of the bore at the top of the rifling lands.

Groove diameter - the diameter of the bore at the bottom of the rifling lands.

Leade - the area of the barrel from where the angle of the throat begins to where it reaches bore diameter.

Not saying this is 100% accurate, but it is how it was explained to me.

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CB posted this 20 November 2007

Here's what we've got. Looking for a competent drawer!!!!!!!

NOTE: Montana Charlie's modification of my (lovely) drawing is included, but invisible, here at “CHAMBER", “FREE BORE", “LEADE” and “THROAT” since the drawing defines these terms.

            A drawing or picture would clear up many of the differences.

 

BALL SEAT

            The cylindrical section of the barrel cut just in front of the cartridge case

Ball Seat is the same as free bore.

 

BORE (DIAMETER)

            The as-made diameter of the bore of the barrel, in .30 caliber, nominally .300"

Now BORE is correctly used in only 2 instances. One is to describe the measurement from the top of one land, to the top of the opposite land, or another way, it's the minor diameter within the barrel created by the cutting of the grooves. The second way BORE may be used is when describing the ENTIRE interior surface of a barrel, as in, “The bore of my rifle shines.” This includes both the lands and the grooves.             Bore diameter - the diameter of the bore at the top of the rifling lands.

 

 

CHAMBER

           

 

FREE BORE

In a rifle chamber throat is also known as freebore and is supposed to be groove diameter with the rifling cut out.

 

Free Bore - the portion of the barrel from the end of the chamber to the beginning of the throat that is free from any rifling.

 

GROOVE (DIAMETER)

            The as-made diameter of the groove bottoms of the barrel, in .30 caliber, nominally .308"

The groove is exactly the dictionary definition . It is a narrow area where material has been removed from a surface and lies at a lower level. In saying, “My groove diameter is .308” describes the major internal diameter of the barrel, from groove to opposing groove. Or as an imaginary circle drawn perpendicular to the axis of the barrel and touching the bottom of each groove.

Groove diameter - the diameter of the bore at the bottom of the rifling lands.

 

GROOVE DEPTH

            The distance from the bore to the bottom of the groove, in .30 caliber, nominally .004".

 

LEADE (LEAD)

That section of the bore of a rifled gun barrel located immediately ahead of the chamber in which the rifling is conically removed to provide clearance for the seated bullet. Also called Throat or Ball Seat.

Another valuable term is LEADE. This is the area of rifling (lands) that begins at the end of the throat, and extends to the point where the lands attain their full height.

 

Leade - the area of the barrel from where the angle of the throat begins to where it reaches bore diameter.

 

THROAT

            The barrel from the end of the cartridge case to the place where bore and groove diameters are not cut.

            I believe “throat” describes everything ahead of the 'chamber' that is involved in transitioning from that chamber to the rifled bore

            In a rifle, the throat is the unrifled portion of the barrel between the chamber mouth and where the lands begin.

            On a revolter, throat is the part of the chambers at the front of the cylinder where the boolit rests (or should), )

in a rifle chamber throat is also known as freebore and is supposed to be groove diameter with the rifling cut out (lotsa throats in rifles are whatever size/shape they are).

Throat - the section of the barrel that begins at the point where the rifling starts

 

 

 

 

 

 

 

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CB posted this 20 November 2007

Gee whiz Joe, I thought you had the terminology settled?  Pacific Tooling calls the ball-seat the 'lead' and the angled section the 'throat'. Clymer calls the ball-seat the 'free bore' and the angled section the 'throat'. Beats me?.................Dan

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Ken Campbell Iowa posted this 04 December 2007

I will only bring this up to be pondered .... no replies please until after xmas, otherwise Santy will not bring me any trick shooting equipment .....

uh..... I havent seen much discussion on this thread about that little space between the front of the case and the start of the ball seat ... usually ground out to about 45 per side stepdown from outside of case neck diameter to the start of the ball seat ... on your 308 W chamber, from say 0.340 down to 0.311 ... that little corner.. space ... silly little lead catcher ...

This is actually not understood too well, but at least in rimfire is important, because some guns don

... and for those of you who shoot the shorter 38 specials in 357 Mag chambers, because 38 brass is cheaper ... heh heh, you may have noticed a difference in accuracy.

If you think about it, when fired, the bullet metal probably is * obturated * to fill that little space and then is squoshed back down at the 45 degree shoulder to the diameter of the beggining of the free bore ....

This is not always a trivial thing, although we usually ignore it as just something to complicate our lives.

Remember, no discussion until next year ( 2008 ) ... just don

Oh yeah... there is such a thing as a chamber whose free bore is the same as groove diameter .... a competition match chamber for a heel bullet ... as in .. uh ... a .22 rimfire ( owch ) ... or my soon to be tested 20 gauge slug gun project.  Anyway, the chamber neck diameter is also the same ... or vice versa ...

regardez, ken campbell, deltawerkes

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