Bore measuring

[82Tank]

Let me say that I am sure that this has been addressed before but I couldn't find a previous thread by searching for "meauring barrel" (or I should say I found too many).
I have 'slugged' the barrel of my Navy Arms .58 buffalo hunter using Rotometals' Roto158-190. Now, how do I properly measure the slug to determine correct Minie diameter for a sizing die? There are 3 lands and 3 grooves on the slug (mirroring barrel), so there is nowhere that a caliper can measure a direct diameter. I am a semi-retired DoD missile engineer, so I am familiar with proper measuring techniques and instruments. I also have a set of snap gauges for measuring internal diameters, but - same problem.

Any assistance will be greatly appreciated.

Thanks

 

[bang]

See if I can get this right.
Measure the thickness of barrel at a land.
Double it.
Measure overall of the barrel.
Subtract the first number from the overall.
It will get you fairly close.

You can trial and error.
Cast or buy some minis. Make a sizer and make it slightly under size. Run a mini through it and check fit. Open the hole in sizer with an adjustable reamer a tad then try again.

The buffalo hunter is a cut down zouave. I have both. Mine uses a very slightly sized .575 mini. I made my sizer just as described above. I cast with a lee mold. The sizer just scrapes mostly at the mold seam. Shoots good with 65 grains fff.

 

[dave951]

Pin gauges are your friend. If you've been in a machinist environment, you'll know how to use these. To get minies to shoot accurately, you have to know that bore size exactly and make your minies accordingly. A pin gauge is the only economical method. For most 58cal, you don't need an entire set, only .575, .577, .579 and .581

 

[M. De Land]

Let me say that I am sure that this has been addressed before but I couldn't find a previous thread by searching for "meauring barrel" (or I should say I found too many).
I have 'slugged' the barrel of my Navy Arms .58 buffalo hunter using Rotometals' Roto158-190. Now, how do I properly measure the slug to determine correct Minie diameter for a sizing die? There are 3 lands and 3 grooves on the slug (mirroring barrel), so there is nowhere that a caliper can measure a direct diameter. I am a semi-retired DoD missile engineer, so I am familiar with proper measuring techniques and instruments. I also have a set of snap gauges for measuring internal diameters, but - same problem.

Any assistance will be greatly appreciated.

Thanks

With a conical (slug) you want to fit to bore diameter in a musket not groove diameter so a simple pin or ball gauge in the end of your barrel will get you there. Remember a slug from a rifle barrel is showing the inverse of the barrel interior profile.

 

[82Tank]

What is an economical source for those pin gages?

Pin gauges are your friend. If you've been in a machinist environment, you'll know how to use these. To get minies to shoot accurately, you have to know that bore size exactly and make your minies accordingly. A pin gauge is the only economical method. For most 58cal, you don't need an entire set, only .575, .577, .579 and .581

What is an economical source for those pin gages?

 

[dave951]

What is an economical source for those pin gages?

What is an economical source for those pin gages?

Amazon. They're about 6$ ea.

 

[82Tank]

Thanks. That's just what I need.

 

[ohio ramrod]

Actually there were some micrometers made for measuring three fluted taps . You can make a simple one by taking a piece of metal with a ninety degree "V" cut into it and place it on the mic's anvil. Then use a round rod to get an "indexing" point. then place your three fluted slug on notch and get the comparason.