Jag size

[No Powder]

I don't always remember very clearly what I read. I am presently having one of those moments. I thought I read that a jag should measure approximately .040" less than the bore size. After measuring several of my jags, I'm finding some variation. I know the size of the cleaning patch has a lot to do with it. But am I remembering correctly, or am I way off base?

[Bigsmoke]

Tom, It has been many a moon since I made any jags for anything, but I think that .040" would result in a lot of lost patches. 
When we were playing with the big bore guns, I had to make cleaning jags for them.  I found early on that even the best of gun shops didn't carry anything for 8 and 4 bores.  Narrow minded people.
I would go .030 instead.

A couple of hours later:
I really got to wondering about this so using my occasionally accurate dial indicator thingie, I first measured the bore of my .54 rifle.  This is a barrel rebored to .54 from the original .50 cal.  It came out .548, groove to groove.
Then I measured a .54 cal jag.  It came out .511 on a jag made by Treso lo these many years ago.
So, it comes out .037.  Pretty close to .040, Tom.

John

[No Powder]

John, I agree with your .030" being the measurement that makes the most sense. I did as you, and checked some jags. But since I have a hard time getting an inside measurement, I just went with a 50 cal.  being .500", and a 54 cal. being .540. Most of the 54's measured around .490. Not what I was expecting. And the ones that really surprised me were the TC 50 cal. jags that measured about .423". So once again, I'll use the Keep It Simple Stupid method (KISS), and use them if they work.