I want to tell you about my experience with firing pin springs. The gun is a Stiller Viper LV in 6ppc with Krieger barrel. I installed one of your firing pin springs with a shim to give 23.2 pounds at cocked length. Pin fall is .220", protrusion is .060". August 2018 at a small match in Selkirk Manitoba Canada the gun shot a .1760" agg and won 3 yardages. https://benchrestforum.ca/index.php?topic=1315.0
May 30th 2019 I installed a Duo spring with no shim, 24 pounds at cocked length and tested a new lot of Barts 65 grain boat tails. The gun agged .3062". Either it didn't like the new lot of bullets or the Duo spring, which gives a big WHACK! and the crosshairs jump.
I put your spring back in, the same one that I shot the teen agg with and the gun agged .210" in the next test.
What does this prove? I can take a proven good shooting gun and knock it right out of tune with the wrong firing pin spring.
I recommend a Duo spring to everybody I shoot against.
Kenora Ontario Canada