Miller,

I took my measurements with small hole gauges and a 0-1" micrometer. Groove diameter with calipers and measuring over the nibs with the mic. Depth was taken with depth stem on digital calipers and repeated 3X with same reading. I will get a cast but it will be a day or several. Wish I had taken some pictures before I started. The gun had been tucked away for 30+ years and showed it.

Thank you again,

John