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I wanted to slug the bore and cylinder throats of my new RBH .45acp/.45LC so I went out and bought a box of .457 round balls the other day. Just this evening I had a chance to slug the .45LC cylinder and the barrel. The barrel miked .451" plus a ten-thousandth or so and the cylinder throats ran mostly .451" minus a ten-thousandth or so. The barrel seemed tightest at each end of the barrel. After starting the round ball at the muzzle, with a plastic mallet, it slid (with vary little effort needed) to the throat of the barrel where it had to be assisted out with a bit more effort.

Looks to me that I have to open the cylinder throats up by a ten-thousandth or two. What would you think is the best way to do this.
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Ted

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Are you sure you need to open them up. If the gun shoots well I wouldn't. I had a .44 S&W with open throats and it leaded the barrel really bad.
 

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opening throats

Are you certain the throats need opening? A ten-thousandth is mighty small.. In any case if the gun shots OK I'd leave it alone. The easiesdt and best way to open throats is the Clymer made jig sold by Brownells. In your case I don't see enough difference to be a problem... The worst thing I would say you found was the differences in the bore's diameter. The tightness at the throat is caused usually by the stress the constriction of the receiver ring that at the muzzle is puzzleing. Are you certain what you felt wasn't just normal engraving pressure. To check, insert a soft lead slug into the bore(slip fit). Then used just under bore diameter BRASS rods and a hammer gently upset the lead slug to a tight bore fit while it is near the center of the barrel. Lube the bore beforehand with sizing die lube(I use STP). you can then get an accurate reading of the tightness of the bore at each end. The tight area at the muzzle is not as 'bad' as the tightness at the throat. The only fiz is to lap the bore at the throat to relieve the constriction. Remember the slug measurement you have is the measurement at the point of smallest bore diameter. A little 'choke' at the muzzle is actually a good thing!Ig your not familiar with lapping technique it may be best to find a qualified pro.
 

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If your within .0002 then your probably wasting your time. Thats too close to consider a problem. KN
 
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