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"Bad Joke Friday" Dan (moderator emeritus)
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Discussion Starter #1
It's my understanding that when cast bullets are used, the bullet should be .0005 to .0010" larger than the barrel groove diameter. And ideally, the cylinder throat will be .0005 to.0010" larger than the bullet.

I have a SBH with a .430 grove diameter barrel, but the cylinder throats are oversize to .436. What is the impact of this level of oversize throats?

It's also my understanding that you select the bullet dia. to match the cylinder throat dia. and not the barrel diameter. But .436" throats sure makes that questionable.

Dan
 

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The Hog Whisperer (Administrator)
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36,305 Posts
You just never know.

I have a "200th year" .45 Blackhawk, and cylinder throats measure about .456" or so, with a groove diameter around .452."  Theoretically, it shoudn't shoot worth a crap - but does with 300 grain and heavier hardcast (and jacketed).

My guess - emphasis on "guess" - is that those bullets are long enough that the nose of the bullet reaches the forcing cone and get centered up, while the case is still holding onto the base.

Anyway, back to your problem - I wouldn't hesitate to shoot .432" bullets through it.  0.002" oversize won't hurt, and you're not likely to find anything bigger, anyway.

Try it and see - you never know.
 

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Super Moderator
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3,365 Posts
Dan,

I've not heard of a SBH with throats that huge!  What method did you use to measure them?  If they are really that big, I suggest sending the gun back to Billy Ruger!  That CERTAINLY isn't in spec, and they should swap you out a new cylinder at no charge!

.432" bullets will shoot better than those sized .429"-.430" to be sure, but .436" is huge, and I don't have any bullet capable of being sized that large... don't think that I would advise doing so either!

Let me know how you measured the throats of your cylinder chambers.

God Bless,

Marshall
 

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"Bad Joke Friday" Dan (moderator emeritus)
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7,762 Posts
Discussion Starter #4
Marshall,

I measured them using two different processes. The first measurement was via slugging. I had previously purchased a Meister kit for slugging barrels/cylinders. I pushed the slugs from inside the cylinder outwards through the throats using a brass rod and three pound hammer. Because of the level of oversize measurements (they all were within .0005 of each other, I also used a telescoping guage to double check. This guage is spring loaded and pushes outwards against the walls and locks in place. You then measure the end result.

I used a good quality micrometer to do the measurements. This revolver has been particularly flustrating because of accuracy inconsistency so I started checking things out.  When I saw the measurements, it occured to me that these throats aren't doing anything to help align the bullets before they enter the forcing cone / lands area?

I do have access to several gunsmiths locally, so based on your indication they are out of spec., suggest I have them confirm my measurements.

Appreciate your information and will follow-up. I'd prefer to not have to pay for a new cylinder, and if they're out of spec. would be able to send to Ruger for corrective action as you suggest.

Dan
 
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