RIFLING TWIST RATE DETERMINATION?

[Bill Paton]

Does anyone have experience using optical methods (bore scope) to accurately determine the rifling twist rates of antique barrels? Running a tight patch down a corroded bore risks getting stuck deep inside the barrel.

Bill Paton

[rich pierce]

I would take a long stiff wire, bend an L with the height of the L less than bore diameter. Follow one land that is on top or aligned with the top flat for example.  Slide the wire down the barrel while looking at daylight until it is exactky where the land twists 180 degrees and is on the bottom.  That length is half a turn.

[WadePatton]

No, but also wondering if a slug cast of Cerrosafe could be used in place of a snug patch on jag.  About 400f less heat required to melt than lead, but possibly durable enough to work through corrosion. 

I've never tried it personally, but if it crumbles or hangs up, boiling water melts it again.

[Daryl]

A cerosafe slug cast in the bore will quite likely be too tight/hard & will flow into the pits, binding it in place.  I'd try Rich's idea.

Barring that, a bronze bristle brush that is tight, will follow the bore well then would have to be turned at the breech to bend the bristles to allow it's removal. 

A tight, lubricated wool mop on a cleaning rod could also be used and will come out easily. I would try the mop first.

A tight patch jammed, should easily be removed with a worm or even a ball-screw.