Old thread, came across on search and wanted to help next guy.
2 types of tunes on these. On mine you need to heat up the red locktite and put 3/16 punch through. I drilled out for 1/4. But had to sand the burrs off.
Replace the original and it is quite again. After 100 sind rounds started moving again. Thinking should lube it for range work.
Putting action back in and reassembly is tricky. I put it back in without everything on the tube. The pulled slightly apart to put it all back together.
I don't have spotting scope. But 3rd shot seems to open a little. First two are inch or less, on my starting loads.
I am having trouble deciding on next load with imr 4350, they were all similar.
Hunter, which is higher pressure caused problems and stuck cases.
What I don't like is you have to rack it hard or will fail to fire. Also can be funny feeding if laying on bench or odd posistion.
I like to load one in chamber first, for hunting.
They also replaced with dust cover with plastic to quite it up. Midway has parts.
I just put timney trigger in, dropped from 4.5 to 2.5lbs. I don't know if that was original. Since light for the era. No creep. I'd be tempted to just replace spring.