In order to get the best performance from a barrel, it's often best to "slug the bore". This involves tapping an oversized ball down the bore with a brass rod. It thus "copies" the rifling, and lets you measure the resulting slug indicator. You can determine how deeply you feel the projectile needs to ride in the rifling. This is the best way to start. You can't just go on ... "it's a 45 caliber". Well, that can be any of a wide variety of sizes. I'm sure you know that Hornady makes .452", .454", .457" ball. Just to name a few. There are .459" slugs for some guns. All "45's".



Here's a pic of the barrel series I was shooting the other day.



Here's one of my test "bore slugs".

Gary

I've heard of slugging the bore on an old rifle that you don't know what size it is. But, you made this barrel. How does slugging the bore help? Don't you still have to get to the range to determine what the right size slug or ball really is?

Slugging is usefull, even though Gary made this barrel, because each barrel made is really unique, in and of itself, and having an accurately formed and measured slug gives a starting point for experimentation.

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Hello Scott,

Prior to making the tooling, from which to make the projectiles; I always slug the bore. This takes a print of the rifling. I determine the depth to which I want the slugs to ride. I then make the "cherry" or machine cutter with which to cut the bullet molds. I have to make that oversized, in order to be able to size the slugs back to uniformity. Quite a bit of work. Quite a few judgement calls as to size really.

The tooling stresses the barrel during button rifling. It displaces the steel for the grooves, rather than cutting away the material. Thus, the size of the rifling button is "not" the actual size of the bullet. The steel actually swells around the button, and then contracts behind the button after it's passed by.

"Slugging" the bore tells you exactly what you got for your efforts.

Gary

nice pics shows the rifling really well , its all in the details ,

Gary,

Do you keep bore slugs for all the rifles you make?

Keith

The information is recorded in the shop and range ledgers. Some of the slugs exist ... but the shop historian is behind in cataloging them in the little green felt lined oak drawers.

Gary

Gary,

Now that's impressive. I would have thought you had a box full of the slugs in plastic baggies with hand written notes on the bags. Maybe even seperated by year of manufacture, but I like the felt lined drawers better. Are they in your office above the workshop?

Keith

The management has been slow to finish the office above the workshop. There is, indeed, a second floor (which management built when I ... I mean they, built the building. However; the office area contains "stuff" and my engraving bench area. The remainder of the second floor is the anodizing shop and bath.

Management was greeted with a wonderful opportunity to "further study" the office complex; by the positive advancement of my lower back condition.

Gary

Since we're opening up airgun posts again; here's a blast from the past. Gary has another thread regarding liners and such and recommended sizing for consistency after determining the best size/slug. Well, here's a refresher on getting started on the path to getting the best size figured out.