Measuring bore size of odd number groove bores?

[Catpop]

How does one measure the bore size of an odd number groove bore, i.e., without opposing grooves such as 5 as in my 1982 SW 629? Thanks in advance, Catpop

 

[243winxb]

Read info at link.

HOW TO Measure Odd Number Groove Diameter
The following question was posted on the old "ASK EACH OTHER" forum by ccrider on 09/20/2009:
"Can some one explain how you measure a slug from a 5 grove barrel so as to determine bore size?"
It was answered by Bob S Posted - 09/20/2009:
"Wrap the slug with thin shim stock; mike the shim stock first, it may not be "as advertised". Wrap the slug tightly,
and mike the resulting wrapped slug very gently, so you don't compress the shim stock into a groove in the slug
(which is an imprint of a land in the bore). Subtract twice the thickness of the shim stock, and that is the groove diameter."

http://forums.thecmp.org/showthread.php?t=3255 Google is your friend. I find .430" cast/sized diameter bullets to work great in a 44 mag. Ruger or Smith. No shim stock? Use a soda can, cut strips.

 

[Catpop]

243winxb,
After reading your post half a dozen times, I think I figured out the directions should start with, SOFT LEAD SLUG THE BORE, then on with the directions furnished. Once I got that through my thick skull it made perfect sense!
Thank you so much! Catpop

 

[243winxb]

When i was young and not to smart, I slugged my bores by loading lite target loads with oversize cast bullets and shooting them into a large 30 gal trash can filled with water. Place old news papers or phone books on the bottom. Stand on top of a wall, shoot down into the water. You will get wet. Not a good method, but works. You may get a hole in the bottom of the trash can with the 44. There are standard cast bullet diameters that work well in many firearms. I would not go to the trouble of slugging a barrel until i had an accuracy problem.

 

[243winxb]

The link is slugging the bore of a a 1873 45-70 Springfield Trapdoor rifle. You can not do that with a handgun and i would not use a wood dowel. http://forums.thecmp.org/showthread.php?t=3255

 

[fecmech]

If you carefully turn the slug in the mic jaws you will find a point where you are just leaving the edge of one land and just starting on another. It is a very small but measurable window. I have done it many times on many S&W's.

 

[stu1ritter]

Me thinks you need to measure the cylinder throats rather than slug the barrel. In a revolver, that's all that really matters. Have a bullet that just pushes through the throat. My 629-3's throat measure at .430 and I size my bullets to .430.

Stu

 

[Sam1911]

Me thinks you need to measure the cylinder throats rather than slug the barrel. In a revolver, that's all that really matters. Have a bullet that just pushes through the throat. My 629-3's throat measure at .430 and I size my bullets to .430.

Yes, sort of.

You DO need to measure your cylinder throats, but if they are smaller than groove diameter -- which happens too often -- those need to be reamed to proper size. Then you still need a bullet properly fitted to the bore.

Swaging down a bullet by putting it through undersized throats will get you poor results no matter what size bullet you started with.