Thread Choke Question

[oldhenry]

I've checked a few of my revolvers for thread choke previously & fortunately none were afflicted with this malady.

Ruger returned my GP100 Lipsey .44 spec. for the 2nd time yesterday. While cleaning it after a 100 round session I discovered some peculiar marks in the bore. They are located @ the forward edge of the frame to bbl. junction. Three are in the grooves & two are on the lands. They seem to be perfectly square (size of groove & land width). One of the marks in a groove is more obvious than the others.

All marks are in alignment with each other.

Is it normal for thread choke to be visible?

I attempted a photograph, but all that came through was a close-up of the muzzle & a light @ the forcing cone.

I plan to call Ruger Monday about this & the .004 end shake/.010 cylinder-to-bbl. gap.

Henry

[oldhenry]

False alarm.

I should have slugged the barrel before suggesting the unusual marks could be thread choke.

I slugged the bbl. this afternoon & there is no thread choke. Surprisingly enough the grove dia. is a consistent .431.............which is puzzling since my Lipsey .44 spec. flat top slugs out @ .429.

The 5 square marks in the bbl. remain a mystery.

Henry

[Don Purcell]

What is the diameter of the cylinder throats?

[oldhenry]

What is the diameter of the cylinder throats?

In it's present condition the cylinder throats are the best assets: uniformly .43150.
I was told today that their bore tolerance is .429 to .431.

I worked on the bore last night with JB Bore Paste & the bbl. bore marks look better, but remain. A nearby rifle builder has a bore scope & I have an appointment to see him tomorrow.

Henry