Slugging a barrel

[Mike from OK]

What is the best procedure to get a slug for accurate measurement?

Mike

[bob in the woods]

I have , in the past, simply driven a lead slug through the bore. [ breach plug removed ]   Today, I have some cerosafe that works well.  I put a plug down the barrel  with a wire running through and then pour in the melted cerosafe. It will harden and then shrink enough to pull it out . It then expands to the correct dimension which is easily measured.

[Mike from OK]

Thanks Bob!

Mike

[J Henry]

JUST THE WAY I DID IT,  Take a 12" long brass rod that just slides down the barrel,slid it down the barrel,now take a soft lead slug/round ball and drive it into the barrel about 4",NOW turn the rifle upside down and shake it up and down ,like your churning butter. The brass rod will slide up and down driving the slug out and the brass rod will come out to.Now take a Micrometer and measure the slug/round ball.Easy as that," Told to me by a 95 year old Master Gunsmith" Worked slick as a smelt. and you do not have to go to all the extra of pulling the breech plug .K.I.S.S.

[Semisane]

JUST THE WAY I DID IT,  Take a 12" long brass rod that just slides down the barrel,slid it down the barrel,now take a soft lead slug/round ball and drive it into the barrel about 4",NOW turn the rifle upside down and shake it up and down ,like your churning butter. The brass rod will slide up and down driving the slug out and the brass rod will come out to.Now take a Micrometer and measure the slug/round ball.Easy as that," Told to me by a 95 year old Master Gunsmith" Worked slick as a smelt. and you do not have to go to all the extra of pulling the breech plug .K.I.S.S.

Yep, that's what I do also. Works fine, but let me add two things. (1) Make sure the bore is very clean and well oiled. (2) Brass is nice, but you can use a steel rod - even something like a length of re-bar - if you put two or three wraps of duct tape on each end of the rod to prevent direct contact of the rod with the bore.

[Daryl]

Another way, one I have used numerous times is a bit simpler. I drive an oversized pure lead ball into the muzzle. Turn a ball screw into it and pull it
out with pliers and measure with mic or calipers.
The thin tine/jaw ends on the calipers will measure groove dia. quite easily if even numbered groove and lands. With a bit of finessing, one can get a reasonable
 measure on odd numbered rifled bores & grooves as well.

[rich pierce]

On originals I pound a slug in and drive it out the breech because they are seldom uniform end to end unless pristine.

Unless a barrel is coned or an original that may vary end to end I’m not sure why slugging is better than calipers at the muzzle. For bore diameters up to .450 or so I have used telescoping ball gauges. They can be inserted a couple inches also. Then measure using micrometer or caliper. In reality if a bore is .499 or .502” it’s not going to make much difference in the ball size you’ll end up using. Try a couple ball diameters and patch thicknesses as usual.

[Daryl]

LOL- I have a set of those expandable ball gauges. Thanks for reminding me, Rich.

[Mike from OK]

Thanks all.

Mike

[Daryl]

The expandable balls will only measure bore diameter. When thinking patch thickness, one must or rather should know the groove diameter.
Taylor and I went out to the range today, shooing our BP shotguns for load/patterns testing as well as some plinking with our squirrel rifles.
I found a .360" ball (cast in Lyman mould by the look of them. I wish I new where I got them from) loaded almost as easily as the .350's in my Rice 36 bl. using the same .020" duck material patch (caliper measure crushed).
Loading was with my tapered 5/16" to 1/4" hickory rod.
Think we might get out this coming week and shoot the trail with them.