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Slugging Rifle Bore?

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Guys I just bought a new Minie rifle and am wondering the best and easiest way to determine bore diameter so I’ll have an idea of where to start with molds and sizers.

I’ve read several often convoluted methods. I do not want to have to pull the breech plug. Guys is there a simple way?

Thanks,

-Smokey
 
I’ve read you can take a piece of thick brass rod stock and put it in the bore, then hammer a round ball into the muzzle and use the piece of brass rod as a sort of slide hammer, turning the gun up and down, dropping the rod down onto the ball until it pops out.

Seems like a good idea to me? I have a .577 Enfield and a 1/2” thick 12” long brass rod, so am thinking I need to procure a maybe .60 cal or so lead ball? Anyone here have one around that size I could buy?
 
See if you can find a machinist with a set if pin gauges.
Pulling your breechplug is not much of a help anyway unless you a 3 flute anvil micrometer to measure the slug.
 
With an odd number of lands and grooves, the measurement of a bore can be an exercise in measurement precision. Any measurement of the slug will include the depth of the groove. Write down the measurement of the widest measurement of the slug. Then, using the depth side of your calipers measure the height of the groove above the bore. This groove depth is hard because it is so awkward. Once you have a depth subtract that from the overall measurement to have the land to land diameter. Now you have a diameter (less 0.001 to 0.002") for your minie ball.
 
Brass rod or similar in bore. Slightly flatten .577 or similar ball and use hammer/mallet against wooden dowel to get ball into barrel.
The technique you stated works well; simple, cheap.
 
Smokey, there's my way and those other ways. Mine isn't the most exact but it works for me so here goes.
Use some minies that are larger than your bore diameter. Hold on real tight to the nose of a minie with a good pair of channel locks and screw the minie base down into the barrel, using the rifling lands to turn down the diameter of the minie. Go as far in as you can to get the entire barrel bearing surface of the minie machined down. then use a pair of dial calipers to measure the minie diameter. Have the jaws of the calipers aligned lengthwise down the minie rather than perpendicular to its centerline. Take lots of measurements and write down the largest.
Then try it a few more minies until you're satisfied that you're getting really good at it and know what your bore is like. Checking how the turned samples fit in the bore should let you come up with the minie diameter.
 
So what exactly are you calling a "minie rifle"?

Assuming you're speaking of a type of ACW rifle, slugging the bore is pointless when you can use a pin gauge to determine actual bore size. They're cheap and on sale on fleeebay.

We in the North South Skirmish Association compete with ACW era arms. On the subject of guns that shoot minies-

1)The marked size on the barrel is very, very often different from actual size.
2)Use a pin gauge to determine actual size.
3)Cast and size minie to .001 under bore. Use only pure lead.
4)Use only real black powder
5)Most accurate charge level is about 60% of service
6)Avoid CCI reenactor caps like ebola pills
7)Decide on lube. Avoid anything with a petroleum origin. This will take some experimentation to determine what works best.

It will take lots of experimentation to get the best and most accurate combination.
 
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