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Naphtali
02-02-2011, 02:53 PM
Please identify micrometers that can measure I.D.s of barrels, odd and even numbers of grooves.

MtGun44
02-02-2011, 03:16 PM
Can't easily be done directly with any accuracy, you are measureing down in the grooves. Search
this site on 'slugging' your barrel. Look on Enco tools for an affordable micrometer that will read to
0.0001". Fowler brand is usually available under $35.

The basic process is to drive a soft lead ball or slug through the lubricated barrel and
measure the slug with the micrometer. DO NOT use a wooden dowel as they can fracture
on a long angle and the two pieces can wedge almost irremovably in your barrel. Brass rod
or steel rod with a .25 ACP case works fine for larger bores.
Bill

Hip's Ax
02-02-2011, 03:22 PM
And for an odd number of grooves you slug and measure from a groove to a land then find the largest gage pin that will fit down your bore, a little math and you have your groove diameter.

I was worried about getting this wrong on my Schmidt Ruben 1889 so I sprung for a v anvil micrometer to measure the slug directly. I got the same exact number as I did from the slug and the gage pin method.

alamogunr
02-02-2011, 04:05 PM
And for an odd number of grooves you slug and measure from a groove to a land then find the largest gage pin that will fit down your bore, a little math and you have your groove diameter.

I was worried about getting this wrong on my Schmidt Ruben 1889 so I sprung for a v anvil micrometer to measure the slug directly. I got the same exact number as I did from the slug and the gage pin method.

Thanks. I've got a V block I bought from a member here. I'll check results using your method. It will be more of a check on me than on the tools.

John
W.TN

bigdog454
02-02-2011, 04:12 PM
MSC has digit outside mics for $19.99 0-1 in. usually they are 55.57 I just ordered one to have for my son to use (won't let him take my Starrett ), made in China but seems well made. I will check it for accuracy supposed to be accurate to .0001.
0-1 in is order # cn76359916
I have no stake or interest in the Co. just thought that I'd pass the info on.
BD

Char-Gar
02-03-2011, 12:33 PM
[QUOTE=Hip's Ax;1146638]And for an odd number of grooves you slug and measure from a groove to a land then find the largest gage pin that will fit down your bore, a little math and you have your groove diameter.

I don't know how math will give you the groove diameter. Rifle barrels differ in the depth or the groove vis-a-vi the height of the lands. Even if you have the paper specs of a barrel, that could be wrong. If you went by paper specs, there would be no need to measure.

theperfessor
02-03-2011, 01:05 PM
I can see how Hip's Ax method works. If the land (bore diameter) is .350 and a land to groove measurement is .354, then the difference between the two values is the groove depth. Double that difference and add that to the bore diameter and you have the groove diameter. This assumes of course that you can get the micrometer anvil all the way down on the bore diameter part of the slug and not catch the edge of one of the groove diameter sections.

alamogunr
02-03-2011, 01:14 PM
I can see how Hip's Ax method works. If the land (bore diameter) is .350 and a land to groove measurement is .354, then the difference between the two values is the groove depth. Double that difference and add that to the bore diameter and you have the groove diameter. This assumes of course that you can get the micrometer anvil all the way down on the bore diameter part of the slug and not catch the edge of one of the groove diameter sections.

A blade micrometer would be able to make this measurement.

John
W.TN

MtGun44
02-04-2011, 05:22 PM
"Blade mic" - difficult to use accurately down in a hole, what about muzzle wear?

Slugging is more reliable, and really pretty simple. Wrapping .002" shim stock
around the slug and correcting for the shim stock has been suggested, but a
V mic is the real solution.

theperfessor
02-04-2011, 05:27 PM
The blade mike would be used to measure the land to groove size of the slug and wouldn't need to be inserted into the muzzle.

Hip's Ax
02-05-2011, 01:44 AM
I can see how Hip's Ax method works. If the land (bore diameter) is .350 and a land to groove measurement is .354, then the difference between the two values is the groove depth. Double that difference and add that to the bore diameter and you have the groove diameter. This assumes of course that you can get the micrometer anvil all the way down on the bore diameter part of the slug and not catch the edge of one of the groove diameter sections.

Bingo. :)

A fellow that goes by Parashooter on other forums told me to use this method. It worked perfectly but I was a little worried so I bought the V anvil mic and checked the slug directly. the exact same number both ways.

BTW, there are more than one angle V anvil mic available, you have to buy the appropriate one according to how many grooves you have.

MtGun44
02-05-2011, 02:07 PM
OK, perfessor - got it. I misunderstood.

Bill