Slugging the Bore

[Cowboy]

Would like to ask a couple of questions in regards to slugging the bore.

1. Under what circumstances would you consider slugging the bore? What is the main purpose of slugging a bore?

2. How does one go about doing so?

Respectfully, Cowboy

 

[54ball]

1. Measurement of the bore.
2. Cleaning and refreshing the bore with an aggressive compound or even a cutter inlet into the lead.

The most common method is to have a rod in the plugged bore, then molten material is poured around the rod. The rod may have grooves or holes to grip the lead.

 

[necchi]

1. Under what circumstances would you consider slugging the bore? What is the main purpose of slugging a bore?

Guy's just want to know what they have. For the average guy just hunting or plinking accuracy can be found without needing an absolute measurement. But it can matter for distance and/or Bench shooters.

2. How does one go about doing so?

Usually some kind of internal hammer is placed in the bore first. Slide a 1/4 to 3/8 solid brass rod about 12" long in the bore first, then using a soft wood or rawhide mallet a guy can pound an oversize ball in the muzzle (with proper care).
Turn the barrel upside down and bounce the brass rod driving out the lead slug.
Or,
There is a relatively inexpensive product out there called Cerrosafe; https://www.google.com/search?q=cerrosafe&ie=utf-8&oe=utf-8&client=firefox-b-1-ab
The stuff melts at well under 190° (less than boiling water) and can be reused forever.
Use the internal hammer, plug the bore a little past the muzzle with a tight wad of paper and pour the Cerrosafe.
I know folks that plug the bore just past the muzzle and use molten lead too,, but you have to be smart to be able to do that safely.
I'm not going to try to pander instructions for using molten lead.

 

[varsity07840]

If the barrel has an even number of lands and grooves, you don't need to slug it. Use a dial caliper.

 

[Cowboy]

Thanks necchi.

Your reply was very informative!

Respectfully, Cowboy

 

[Cowboy]

My main reason for wanting to slug the bore is more for refreshing the bore than measuring. I appreciate your reply. Thank you.

Respectfully, Cowboy

 

[Cowboy]

Thank you for the information and reply 54Ball.

Respectfully, Cowboy

 

[mooman76]

It's more important to slug when shooting minies. They do best when the minie is .001-.002 under bore size. It's good to know info but not necessarily necessary. Kind of a shortcut to finding what works best.

 

[M. De Land]

Slugging a bore is for the purpose of measuring the groove depth or groove diameter.
The bore of a barrel is the land diameter. This is best measured with pin/plug gauges.
The best method I know of to make a bore slug is to use and under size mild steel rod tape wrapped every three inches to bore diameter then a soft lead slug is drop down bore and another mild steel rod tape wrapped the same way is tapped down on the soft lead slug. The soft lead slug is positioned between the steel rods which expand it from both ends. This will make a perfect impression of the bore interior. It is pushed out and the grooves can now be measured as they become the barrel groove inverse or land on the lead slug.
The tape wrap perfectly protects the bore interior from the steel rod flex.
Odd numbered rifling can be accurately measured with a tri-mic or Powely gauge which is nothing more than a poor mans tri-mic.

 

[M. De Land]

A poured lead slug is for lapping the bore as it will be under size when the lead cools.
The lapping compound added to it is what tightens it up in the bore.
Freshing out a barrel is actually cutting the grooves deeper with a hardened steel cutter and then reaming the bore wider as well.
Lapping only removes a few ten thousands generally and is good for leveling a tight spot in the bore.
It cannot remove pitting over .001 in depth but it will smooth the edges of the pits which is often all that is needed.

 

[Rockthrower]

Cerrosafe is the way to go or just melt some paraffin in a ladle and use it. Wax slugs are easy to remove and are darn accurate.

 

[M. De Land]

I have and use Cerosafe but not for slugging a bore.
It's primary purpose is for chamber casting and measuring and it is time sensitive as it begins to expand after a certain amount of time has passed were as a lead slug remains static.
Cerosafe will expand about one percent in 200 hrs after being cast and will be at measuring diameter in about one hour after casting if memory serves me correctly.

 

[Cowboy]

Thank you for the information Moonman.
Respectfully, Cowboy

 

[Cowboy]

Great Information M.D. , I appreciate your reply and the education as well!

Respectfully, Cowboy

 

[Cowboy]

Thank you for the reply Oakgall. It’s greatly appreciated!

Respectfully, Cowboy

 

[ZUG]

I have and use Cerosafe but not for slugging a bore.
It's primary purpose is for chamber casting and measuring and it is time sensitive as it begins to expand after a certain amount of time has passed were as a lead slug remains static.
Cerosafe will expand about one percent in 200 hrs after being cast and will be at measuring diameter in about one hour after casting if memory serves me correctly.

You are correct -- this is from Brownell's web site "Cerrosafe shrinks during the first 30 minutes of cooling and then at the end of an hour, is EXACTLY chamber size. At the end of 200 hours it will have expanded approximately .0025". Cerrosafe melts between 158° - 190° F. It should be melted in a clean, iron ladle. Source of heat should be removed as soon as the alloy is completely melted, at which time it is ready to pour. The solidified casting should be removed from the chamber before, or when, it cools to room temperature. If allowed to remain in the mold over an hour, it will grip the chamber walls and be difficult to remove"
I would use this method if the breach plug can't be removed and a lead slug can't be driven through the bore. My two cents worth :v .

 

[M. De Land]

I've had to melt Cerosafe out of a chamber several times I left in a scoach to long and it would not budge when I went to knock it out.

 

[mooman76]

Been there done that.