Best freebore diameter, for 6PPC?

Freebore Diameter

I use .2435 like most. Three reasons:

1. It's enough to clean up all trace of the lands in most barrels. If it doesn't, I would be surprised if the barrel turns out to be a shooter.

2. It allows the bullet to seat against the throat without resistance.

3. Anything larger would be unnecessarily sloppy. Keep in mind that a sharp reamer is much more likely to cut slightly oversize than to cut undersize.

I have a resharpened reamer that cuts the throat undersize. I was able to get the first chamber to shoot with the tight freebore, but it was very difficult to get a good seating depth. I used a separate throater to open it up and discovered my first (and only) hummer barrel.
 
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It depends upon the diameter of your bullets. If your bullets measure .2435" then you don't want a .2435" freebore. As long as there is clearance on the bullet, it doesn't make much difference. I've been using .2435" diameter bullets with a .244" freebore diameter and a little less wouldn't hurt anything as long as the freebore diameter is at least a couple of tenths over bullet diameter.
 
Boyd, yes, the bearing surface of the bullet and even the heel on a flat based bullet is what I'll measure. Although, I'm not sure that the heel of the bullet stays that diameter when it's seated in the neck especially if using lots of neck tension. I've never miked a pulled bullet, but might be interesting to see what seating the bullet does to the heel measurement.
 
Mike Bryant said:
I've never miked a pulled bullet, but might be interesting to see what seating the bullet does to the heel measurement.
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I have and they stayed the same, both bt and fb..... but IMO the 600lb push required to start the bullet into the lands DOES do something to the diameter.... ;)

al
 
Al, Sure does but only on a f.b. or should I say only the f.b. increases in dia., its amazing what happens to bases and they still shoot good...
 
geo.ulrich said:
Al, Sure does but only on a f.b. or should I say only the f.b. increases in dia., its amazing what happens to bases and they still shoot good...
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:)

"Explode" a charge of powdered gasoline with a blasting cap, swaging and expressing a lead/copper slug through a grooved tube at high velocity to achieve better intrinsic accuracy than my 5000.00 laser transit is capable of????

Yeahh, that's perty impressive!

al
 
As to freebore diameter, show me a reamer source that you can get the freebore ground that will cut to a specified tenth. You don't want the freebore smaller?? The barrel diameter is!!!

Secondly, how many of you ever mike the freebore diameter, or perhaps a better question, how many of you have the equipment or the ability to measure the diameter of, say, a 0.050" long freebore???
 
JerrySharrett said:
As to freebore diameter, show me a reamer source that you can get the freebore ground that will cut to a specified tenth. You don't want the freebore smaller?? The barrel diameter is!!!

And have the reamer cut X dia. through its life in other words they all wear, better off starting a little larger. How many know the working tolerance of the barrelmakers? that will help with the decision..
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geo.ulrich said:
JerrySharrett said:
As to freebore diameter, show me a reamer source that you can get the freebore ground that will cut to a specified tenth. You don't want the freebore smaller?? The barrel diameter is!!!

And have the reamer cut X dia. through its life in other words they all wear, better off starting a little larger. How many know the working tolerance of the barrelmakers? that will help with the decision..
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Most of the benchrest biggies in barrel making appear to be holding their advertised diameters to about 0.00005. For an example most 6mm benchrest barrels are 0.2430"/0.2370" or 0.2430"/0.2360". The minor diameter can be measured with pins, small hole gages, etc. For the major diameter and since I slug all my barrels I measure the OD of the expended lead slug.
This being said applies to barrels with even numbered grooves. The Spencer 5-groove and Hart 3-groove barrels, for example, pose a challenge to measure.
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Jerry, I mean groove dia. not the tolerances I am getting drop a zero.in other words groove dia. .2430/ .2435
 
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I'll stir the pot a bit. Ever thought about a tapered freebore? Obviously I have. Reamer makers will hate you but .......

Dave
 
Dave Tooley said:
I'll stir the pot a bit. Ever thought about a tapered freebore? Obviously I have. Reamer makers will hate you but .......

Dave
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Toot, tapered a few thousants or a few degrees? I've never had a reamer grinder that could get that close for tapering the freebore for a short range bullet, say 825 jacket and up to a 10 ogive nose. Now then, on a VLD or thereabouts where the bullet is 1" or longer and has a 15 ogive or so nose, I can see that.

I've had reamers ground by KF, HH, DM, DK, RE and a couple of others buy I don't think they CAN work that close.

STIR....STIR...STIR...SWIZZLE
 
If you tapered the free bore wouldn't that become the leade, as in a double angle ie, lets just say .25* into 1.5* ??
 
Kiff will do (does do ;) ) tapered freebores...... and with his 100X OC he gets them perty steenking close!!! They're sure closer than I can ascertain. Tenths become more workable at 100 power.
 
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