HenryC460
06-02-2007, 09:56 PM
S&W 629 44 Rem. Magnum caliber, 5-groove rifling. Haven't shot it yet.
I slugged the barrel and cylinder throats and also made Cerrosafe casts of each. The two techniques were equally easy in my hands.
I ran up against the odd groove problem on the barrel, and not being a machinist, I don't know my groove diameter really. I do have slugs, and I do know that if I just hammer a slug into the barrel, tap it out, and try it in the cylinder throats, it fits. That's good. According to that, my cylinder throats are at least as big as my barrel, and after passing through the throat, the bullets will be at least groove diameter.
End of good news. And it wasn't really great, high quality accurate good news.
If I really make sure that slug is filled out to groove diameter by drilling a hole in it and driving a drywall screw in the hole to really expand the slug, and if I use the drywall screw as my handle and pull the slug out, it does not fit into any of the cylinder mouths. It does fit nicely back in the muzzle, so it's not a delayed springiness of the lead slug. The groove diameter really is a little bigger than the cylinder mouth diameter. That's bad, I guess, since my bullets will be sized to sub-groove diameter by the cylinder mouths upon firing, and hot gases will blow by in the barrel and were all gonna die or go to jail or something.
Cerrosafe casts confirm that my cylinder throats are smaller than groove diameter. Fresh barrel casts enter cylinder throats, but at 1 hr, forget it.
What should I do?
Size to about cylinder mouth diameter (around 0.4315") and shoot the dang thing is the first thought that comes to mind. If it's accurate, no problems. If it's not, then there's the option of selling it. Darn pretty revolver. Also, I suppose the cylinder mouths could be reamed to oh-point-whatever is a little bigger than groove diameter once I figure that out.
That brings up an interesting problem. What if I finally figure out how to measure 5 grooves and my groove diameter is 0.434" (accounting for expansion of Cerrosafe)??? Then what? Sure, I could have the cylinder throats reamed out to 0.435" or so. Then I "simply" size my bullets to the new cylinder throat diameter and try shooting it again. Have I got it right so far?
Then, I need to find nonstandard moulds and nonstandard sizing dies that drop and squish 0.436" and 0.435" bullets and I should (should) have a sweet-shooting six gun.
Anybody know how to actually measure a 5-groove barrel? I've heard of using an expandable ball gauge to get bore dia. and then measuring land-to-groove on the barrel slug, subtracting the two to get groove depth, and adding groove depth to the land-to-groove measurement and call that groove diameter. That sounds pretty sound and complelling to me, but I'm not a machinist. Someone else said carefully twist that slug in the barrel to shave lead off into the bbl. grooves and get a slug that's bore diameter and you don't have to buy a ball gauge that way.
Two babies crying and wife expects help. I'd babble longer, trust me (but if I really had time, I'd edit it down and make it readable). I am guardedly pessimistic about the situation, but if the shooting test says don't worry, I'll stop worrying.
Gotta go, really.
H. C.
I slugged the barrel and cylinder throats and also made Cerrosafe casts of each. The two techniques were equally easy in my hands.
I ran up against the odd groove problem on the barrel, and not being a machinist, I don't know my groove diameter really. I do have slugs, and I do know that if I just hammer a slug into the barrel, tap it out, and try it in the cylinder throats, it fits. That's good. According to that, my cylinder throats are at least as big as my barrel, and after passing through the throat, the bullets will be at least groove diameter.
End of good news. And it wasn't really great, high quality accurate good news.
If I really make sure that slug is filled out to groove diameter by drilling a hole in it and driving a drywall screw in the hole to really expand the slug, and if I use the drywall screw as my handle and pull the slug out, it does not fit into any of the cylinder mouths. It does fit nicely back in the muzzle, so it's not a delayed springiness of the lead slug. The groove diameter really is a little bigger than the cylinder mouth diameter. That's bad, I guess, since my bullets will be sized to sub-groove diameter by the cylinder mouths upon firing, and hot gases will blow by in the barrel and were all gonna die or go to jail or something.
Cerrosafe casts confirm that my cylinder throats are smaller than groove diameter. Fresh barrel casts enter cylinder throats, but at 1 hr, forget it.
What should I do?
Size to about cylinder mouth diameter (around 0.4315") and shoot the dang thing is the first thought that comes to mind. If it's accurate, no problems. If it's not, then there's the option of selling it. Darn pretty revolver. Also, I suppose the cylinder mouths could be reamed to oh-point-whatever is a little bigger than groove diameter once I figure that out.
That brings up an interesting problem. What if I finally figure out how to measure 5 grooves and my groove diameter is 0.434" (accounting for expansion of Cerrosafe)??? Then what? Sure, I could have the cylinder throats reamed out to 0.435" or so. Then I "simply" size my bullets to the new cylinder throat diameter and try shooting it again. Have I got it right so far?
Then, I need to find nonstandard moulds and nonstandard sizing dies that drop and squish 0.436" and 0.435" bullets and I should (should) have a sweet-shooting six gun.
Anybody know how to actually measure a 5-groove barrel? I've heard of using an expandable ball gauge to get bore dia. and then measuring land-to-groove on the barrel slug, subtracting the two to get groove depth, and adding groove depth to the land-to-groove measurement and call that groove diameter. That sounds pretty sound and complelling to me, but I'm not a machinist. Someone else said carefully twist that slug in the barrel to shave lead off into the bbl. grooves and get a slug that's bore diameter and you don't have to buy a ball gauge that way.
Two babies crying and wife expects help. I'd babble longer, trust me (but if I really had time, I'd edit it down and make it readable). I am guardedly pessimistic about the situation, but if the shooting test says don't worry, I'll stop worrying.
Gotta go, really.
H. C.