Just an update on the optional heavier striker springs in case people are wondering... the 80N (18#) and 100N (22.5#) striker springs arrived today.
I did a couple of tests. First I removed the bolt shroud and firing pin assembly, supported the collar near the tip of the firing pin on a digital scale, and pressed down on the bolt shroud to check two measurements: pressure on the spring when it first starts to compress, and pressure on the spring when compressed to put the cocking piece flush with the back of the bolt shroud. One thing to note, with the action fully cocked the cocking piece is slightly below flush with the back of the bolt shroud, so the below measurements take some overcocking into account, which explains why the final spring pressure is higher than ARC's specs.
With the stock 70N / 15.74# spring, it took 12.3# to start compressing the spring and 16.8# to have the cocking piece flush with the back of the bolt shroud.
With the 80N / 18# spring, it took 14.8# to start compressing the spring and 19.2# to have the cocking piece flush with the back of the bolt shroud.
Next, bolt lift effort. I used a hook type scale at the center of the stock hourglass bolt knob. Not the greatest test method, but it was pretty repeatable... I tested each spring 10 times and averaged the numbers.
The stock 70N spring took about 4.75# on average to open the bolt.
The 80N spring took about 5.45# on average to open the bolt. The extra effort is noticeable while running the bolt compared to the 70N spring but it's not heavy IMO, the action still operates smoothly. I'm going to run the 80N spring for a while and see how I like it and see if there's any difference in SD/ES or group sizes. Since I've had no failures to fire with the 70N spring and CCI 450s, and SD/ES/group sizes are all great I may reinstall the 70N spring for the lighter bolt lift and keep the 80N spring in my shooting bag just in case.
I did not test the 100N / 22.5# striker spring as I damn near launched the bolt shroud across the garage just trying to install it. It's much longer than the 70N and 80N springs; it's actually longer than the firing pin and you have to partially compress it before you can start sliding the bolt shroud over the firing pin, and I could not compress it enough to install the cocking piece with only fingertip grip on the two small ledges on the bolt shroud. The 100N spring is a pain in the ass to install compared to the 70N and 80N springs which aren't too bad. I need to make a tool that will grab the ledges on the bolt shroud or engage the two bayonet locking tabs that hold it to the bolt body so I can get a more secure grip on it to fully compress the 100N spring while keeping my fingers out of the way to install the cocking piece back on the firing pin.
Once I make a tool and get the 100N spring installed I'll report back with the actual bolt lift measurement. My hunch is the bolt lift with the 100N spring will be about 6.8#. I'm also pretty sure I won't like the bolt lift with the 100N spring installed...
Here's a pic... stock 70N spring on top (80N spring is the same length), 100N spring on bottom. You have to compress the 100N spring nearly to coil bind to get the bolt shroud down far enough to reinstall the cocking piece.