Ruger Old Model SBH Bore Diameter

I have an OM SBH I have been trying to get to shoot and it has been a struggle. Throat size is .431 and that is what I have been sizing to but still experiencing poor accuracy and leading. Gas check bullets help the leading but accuracy is still mediocre. So I decide its time to slug the barrel and low and behold its .432. So now I need to have the cylinder honed to .433 and get an appropriate sizing die. Fortunately my molds drop large enough with my alloy to make it work.

Gun is an unconverted OM SBH in fantastic condition but I think I am finding out why I got a "Good Deal" on it.
Is anyone else seeing this large a bore with there SBH. Seems on the large side to me.

Thanks
Mike

I have the same OM SBH and it shoots .430 perfectly. But, does lead the first few inches of barrel when sized to .429...

opening the cylinder throats is easy, making them smaller is less easy.
I would re-measure.

No doubt about it, I'm pretty sure my measurements are good though. Slugged the barrel, measured with Micrometer and get .432. Barrel slug wont enter the throats. Measure the throats with pin gauges and get .431. To your point though, I will certainly measure again before the chips fly.

Thanks
Mike

Pin gages are pretty much the last word, but the slug not entering the throats is proof you're correct.

I have a NM SBH with .432 throats, a .430 groove, AND mediocre accuracy. The fault here is an excessively huge forcing cone, so long and cavernous that a 240gr's bearing length is shorter than the cone length, thus allowing the bullet to fly unsupported between cylinder and rifling. I sent it to Ruger, but they said it's "within specs" and sent it back so I'm not sure they'd fix undersize throats.

Send your cylinder to DougGuy here on the board. He will fix it.

That's probably what I will probably do Wayne. Out of curiosity, have others seen a bore diameter this big on their SBH's. The reason I hadn't slugged the bore is that all my Rugers have been spot on in the past and shot well as long as the throats were correct. I slugged this one because the throats appeared ok but I was still having issues.

Thanks
Mike

Quote:

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Originally Posted by yeahbub

...I have a NM SBH with .432 throats, a .430 groove, AND mediocre accuracy. The fault here is an excessively huge forcing cone, so long and cavernous that a 240gr's bearing length is shorter than the cone length, thus allowing the bullet to fly unsupported between cylinder and rifling. I sent it to Ruger, but they said it's "within specs" and sent it back so I'm not sure they'd fix undersize throats.

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I have two Ruger Vaqueros one .44-40, the other .44 Magnum, both have forcing cones so large that .45 Colts and ACPs fit, don't "spit" and shoot accurately down the .44 tubes if I swap cylinders from my NMBH .45 Convertible!

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.432" is a bit odd even for an OM. Try this. Take a plastic cleaning jag and patch it real tight in the clean dry shiny bore. Push it towards the frame and observe how much effort it requires to keep the jag moving. Any change in resistance, is either a tightening or loosening of the barrel. Lots of OM 44s have a loose spot about a half inch long right where the barrel meets the frame. There were more of these slight bulges than there were thread constricted barrels back in the day that one was made.

You have certainly arrived at the root cause of the problem(s) discovering the throats are smaller than the bore. Time to remedy that and it will be shooting lights out!

Outpost, fortunatly my forcing cone looks pretty good.
Doug guy, I'm going to measure again to be 100 percent my finding are correct and send you the cylinder. Life has caught up to me and I won't be able to mess with it for a couple of weeks at this point.

Thanks
Mike

Outpost, have you sent those vaqueros back to Ruger to get those cones fixed? It's really interesting that you shoot .45's through them and still get good accuracy. Any leading? I suppose they're not really stout loads.

I have an Old Model Vaquero in .44-40, but the throats are .425, barrel is .430. It needs new chambers as well as a throat reaming because they won't chamber a round with a .430 boolit anyway.