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Discussion Starter · #1 ·
I have a 1967 K-38 Target Masterpiece m 14-3 that has a constriction in the barrel at the point where the barrel threads into the frame. I discovered this when I slugged the barrel to determine what diameter cast bullet to use. The cylinder throats are .358" I don't know what the last 5 inches of the barrel are, because once the pure lead slug was hammered into the muzzle it was easily pushed toward the frame by pushing on the wooden dowel until it got to frame where it required a few taps with the wooden mallet. After going through this constriction the slug measured only .3505" at it largest diameter.

What can and /or should be done about this condition?
 

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More common than many would believe and depending on degree a great recipe for leading with cast bullets. Some times you can even feel it with a tight cleaning patch. Happens when barrels are crush fit to frames as most are these days. usually happens and to a greater degree in larger calibers (thinner barrel walls ) but possible on a 38 of course.
Good news is it is easy to rectify ,if you have access to reloading equipment. Search every thing you can on "firelapping". Too much info. for me to replicate here but it does work . I've been doing it for a few years , usually get an increase in accuracy and never had get worse.
Fire lapping, sounds creepy but it works.
 
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1st welcome to the forum. I'd make sure there's a problem before I changed anything, chances are good soft cast bullets will swell enough to use the rifling properly & it'll shoot very accurately as is. If not firelapping works very well.
 

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Happens when barrels are crush fit to frames as most are these days.
Actually, pinned barrels are "crush fit" also. When the thread on the barrel's shank is timed to the frame, the barrel is "supposed" to become hand tight about 60 degrees before top dead center. The barrel is then tightened the rest of the way using the appropriate fixtures and/or wrenches. The pin is then installed if it's that type of barrel. The only difference between the the pinned and so called "crush fit" installation procedure is the pin. The barrel does not just spin into the frame like a bolt into a nut and then the pin is inserted. The problem occurs when there is an "oops" in the final machining of the barrel's shoulder and it becomes hand tight too soon. The barrel is then rotated the extra degrees of rotation mechanically which causes the constriction. It's sort of the "when it's not right, get a bigger hammer" method of assembly.

Bruce
 

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Discussion Starter · #9 ·
The Happy Kaboomer, "I'd shoot it first and worry about fixes later if accuracy is not up to par."

1st welcome to the forum. I'd make sure there's a problem before I changed anything, chances are good soft cast bullets will swell enough to use the rifling properly & it'll shoot very accurately as is. If not firelapping works very well.
With this being a "Target Masterpiece" I would hope that the revolver would "shoot better than I can" I know it doesn't shoot better than I can because I have another target pistol that does shoot better than I can, and I can shoot it very well. Not this one.

needmostuff, the article that you linked, "A Contemporary Look At Barrel Leading and Related Sixgun Issues" was very good. I want to firelap this revolver. I don't need 250 pin gauges, however. If I buy individual pin gauges what sizes do I need for this S&W K 38? .3550; .3555; .3560; .3565; .3570; .3575; .3580; .3585, etc. ?

Which brand firelapping kit would any of you recommend? Do these kits include the lead bullets needed for firelapping? The only bullets I cast are 105gr and 125gr.....not enough bearing surface I think.
I appreciate the advice from all of you.

Thanks, Harleyrock
 

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Yo Harley, I never have had the luxury of pin gauges either but you are on the right track if you decide to go that way. I mostly go by pounding soft lead thru the bore and going by feel . Not as scientific but you can get a good feel . Look for slightly oversized sinkers or minie balls. Oil the bore well before starting the lead. A good micrometer is needed to check results and also chamber mouths after slugging.
I use the NECO products sold as a starter kit. 4 grits and some steel plates and an instruction book .It works well and they answer the phone for questions.
The Beartooth site also sells products which I have not tried . If you dig thru the tec notes and F.A.Q. section there are several mentions of how to do's. He does sell bullets and lapping kits.
Kind of a slow ,messy process but it is fun to watch the resulting improvement as you progress.
 
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