Slugging a barrel

[augois]

How does one go about slugging a barrel, and how do you measure the resultant slug?

Also, is the optimal cast bullet diameter .oo2" over groove diameter, or should it be more?

[Shiloh]

How does one go about slugging a barrel, and how do you measure the resultant slug?

Also, is the optimal cast bullet diameter .oo2" over groove diameter, or should it be more?

Many guns will have a different sweet spot.

My Krag does well with .312 boolits, the bore is just under .310 The '03 likes 'em at .004 over bore size. I got the cone shaped fishing weights, lubed it good and drove it down a cleaned bore with a dowel. The Krag was slugged this way and so was the '03. Hand guns barrels and chambers were done with lead boolits and measured. with a caliper. I should really get a micrometer for more accurate results.

Shiloh :castmine:

[ra_balke]

A better way is to slug the chamber throat.

it is not so much that a bullet must fit the bbl, as it must fit the throat.

Fill an empty case with lead. load it into the gun.
Make a chunk of pure lead that will fit down yur bbl, and drive it down the bbl with a rod.

Pound on it till yu feel it go dead.
You will know what that means when you do it.

Take the mess out of yur gun, and measure the throat, and fit yur cast bullet to that.

[Piet]

RA_Balke

Could you please clarify how you fit the bullet to the throat?
Thanks.

[405]

Piet,
By slugging a bore all the way thru you get a slug measurement of land and groove diameter that is the smallest of any part of the bore. By obturating a slug AT the throat you get a "slug" or "casting" of only the throat area. Theoretically this is the critical first area of the bore that tha bullet encounters when it is fired thus the most critical for best fit and minimum leading/blow by potential. For those rifles with throats that are larger than groove diameter the best bullet diameter is theoretically the throat diameter.

You can take an empty case and fill with lead to the mouth. Or use a metal rod that is about a snug fit into the case. Cut the rod to length of the case (even with case mouth). Put plugged case into chamber. Push a soft lead slug down from the muzzle until it stops at the plugged case.... which is the throat area. Use a slug about 1/2-3/4 inch long. Gently tap, tap, tap this slug with the rod used to push it down from the muzzle. It will obturate to fill the throat area. As ra_balke posted- you can feel it quit obturating (goes dead). Remove plugged case from chamber. Gently tap the throat slug on thru. You should end up with a casting of just the throat area and a small part of the bore. Sounds harder to do than it really is.

[Jack Stanley]

RA_Balke

Could you please clarify how you fit the bullet to the throat?
Thanks.

Piet , I've done as 405 described with a fired casing and it works well . I did however resize the case first before filling it with lead . Leaving the fired primer in is a good thing and putting a light coating of lubricant on everything so it would be easier to remove .
Either way will help you get the throat measurements . I've found that bullets sized up to about .0005" over work without problems , the groups you make will tell you what's best .

Jack

[Piet]

Thanks for the information, I will try it.

[fourarmed]

This has been mentioned here before, but it bears repeating: Use a metal (steel or brass) rod that is not much smaller than the bore. Manufactured wood dowels have a tendency to break on a bias and jam in the barrel. If you are worried about bore damage, wrap a little tape around the end of the rod.