Breaching a barrel

[Mark15373]

Hello everyone, I have a question for some of the more experienced guys out there. I acquired an old wreck (.32 cal poor boy) and the barrel had the plug and tang brazen on the back, which I didn't trust to shoot so I cut off 1/2 inch and sure enough my gut was right about 4 inches from the bottom was rusted shut, but has since been cleaned out to functional condition. No touch hole was ever drilled but as for the breech and plug I know you have to drill out a slightly larger size so the plug meets on the shoulder flush to create a seal, but I'm not sure how big to drill it out or the depth, and tools are not a problem I have access to what I need at the machine shop at my work. if anyone has any advice I'd sure appreciate it.
-Mark

[44-henry]

Center it in the lathe using a four jaw chuck. I would bore it out 37/64 (or a hair smaller) at 1/2" depth and thread it for a 5/8-18 thread using a bottoming tap (or single point thread it if you know how). Align your tap with a center in the tailstock to keep it centered. Not much to it if you have a good lathe.

[Bill Raby]

If you don't have a good lathe, send it to Track of the Wolf.

[Mark15373]

@44-henry thank you for the advice, I will be boring it out tomorrow on my lunch break 

[L. Akers]

In a .32 cal. barrel you don't need a plug as big as 5/8ths.  I would use 1/2-20 (.435 bore size ) or 9/16-18 (.490 bore size ) with preference to 1/2-20.  The procedure is as 44-Henry described.  Use a boring bar--not a drill.  You want the bottom of the counterbore to be square to the bore axis to create a shoulder.

[Scota4570]

In a .32 cal. barrel you don't need a plug as big as 5/8ths.  I would use 1/2-20 (.435 bore size ) or 9/16-18 (.490 bore size ) with preference to 1/2-20.  The procedure is as 44-Henry described.  Use a boring bar--not a drill.  You want the bottom of the counterbore to be square to the bore axis to create a shoulder.

I do it with a boring bar too.  90* shoulder and I start the threads on the lathe .  I also make a relief cut to break the final chip with the bottoming tap.    Fancy...

For those not  able to do internal boring and threading, would it be a problem tot have a 60* shoulder instead of a 90* shoulder?  You'd want the plug face to be bore diameter, of course.  It seems a little easier but he same result.