determining bore size with 5 groove barrel?

[mbogo3]

Is there an easy way of determining bore dia with a 5 groove barrel as the lands don't match up?How do you measure a slug? Thanx Harold

 

[sunray]

The same as you do with a 2 groove barrel. Slug the bore and measure the diameter at it widest point.

 

[Al-Sway]

No there is no easy way. It can be done with a V block, some careful measurements and mathematics. Otherwise, as mbogo3 has already concluded, you end up measuring on one groove and one land.

 

[Eagleye]

If you slug that 5 groove barrel, and the grooves are relatively wide, you can actually get a good measurement with a Caliper. Just rotate the bulet till it opens your caliper to the widest point, read the measurement, and you've got it. If the grooves in the barrel are narrow, you must use the V-block, measurement and mathematics to get the job done. Eagleye.

 

[tiriaq]

Bore diameter or groove diameter?
As mentionned, it can be difficult to get an accurate direct measurement from a slug.

 

[grouch]

Maybe if you insert a soft cast bullet bullet with a tapered nose in the muzzle and pushed hard enough to engrave the rifling to full depth and measured an identical bullet at that point you'd be pretty close.....

 

[looch]

Measure barrel wall thickness in several different places, take the average, multiply by 2, and subtract from the barrel diameter?

 

[curtmg]

Measure barrel wall thickness in several different places, take the average, multiply by 2, and subtract from the barrel diameter?

I'm not a gunsmith, but wouldn't that involve drilling holes into the side of the barrel?

 

[Sticker]

Howdy

It's not the kind of thing the average person will buy, but Mitutoyo makes a micrometer for 5 sided stock. It would work great for Enfield rifling and well as Smith and Wesson revolvers. They make a mic for 3 sides as well.

Sticker

 

[looch]

I'm not a gunsmith, but wouldn't that involve drilling holes into the side of the barrel?

"Several different places..." ...around the muzzle. dink.

 

[curtmg]

"Several different places..." ...around the muzzle. dink.

Honestly, it took me until about an hour ago, to realize that's what you meant, usually I'm a smartass, this is the rare occasion I'm more of a dumbass

 

[looch]

 

[mbogo3]

Damned if I didn't choke on my tea! At least he's honest.Too funny.............Harold

 

[maynard]

You guys ever heard of pin gauges?

 

[mbogo3]

Nope?

 

[tiriaq]

w ww.meyergage.com. is where I have bought pin gauges.
A set of pin gauges can be used to determine bore diameter of a barrel with an odd number of grooves.

 

[mooncoon]

I made up several stepped plug guages which give me the bore diameter. They are a series of straight sections going up in jumps of .002" and it is most practical to make them about 10 intervals long and the straight sections about 3/8" - 1/2" long. Groove diameter I guess at based on the most probable rifling depth.

cheers mooncoon

 

[Al-Sway]

Certainly a set of pin gauges could be used, if you wanted to spend a lot of money to check bore diameter.

 

[stocker]

If you want to know groove diameter to determine likely best cast bullet diameter to use pin guages aren't going to help you much but they would tell you bore diameter.

 

[maynard]

Certainly a set of pin gauges could be used, if you wanted to spend a lot of money to check bore diameter.

You can order them for about $4 each. For checking something like a .30 cal you would need .306", .307", .308", .309". If all of these fall thru the barrel it is time for a new barrel