After (finally) getting some Berger 410s in for my 37XC, I was able to get out to a private range to do an initial test using N570. The issue is that I was unable to find any load data whatsoever. As such, I decided to start a thread here for others who might either be using the 410s in their 37XCs or for those who might be looking for information.
For my first foray, all I had to go on was my limited exploration of 390 ATips - my entire previous experience had been with much lighter bullets (Lehigh 353s). With the Lehighs, I had gotten decent results with H1000, but I think that such a speed powder would be too fast for a bullet weighing 57 grains more. With the ATips, I used 120gr of N570 and it seemed to do okay for the limited amount of time I tried that bullet.
For the 410s, I decided to do a shortened ladder starting at 114.5gr and going up at 1gr increments so I could attempt to find pressure. I also loaded up 6 foulers - 3 at 116gr and 3 at 117gr.
Here is the average velocity for each of these charge weights:
Temp: 85 F Humidity: 30%
Seating depth (essentially randomly chosen): .020"
4 shots each, except for the two fouling loads (116 and 117), which were 3 each.
114.5gr 2849 fps
115.5gr 2873 fps
116gr 2873 fps
116.5gr 2886 fps
117gr 2900 fps
117.5gr 2920 fps - very slight heavy bolt lift
118.5gr 2935 fps - heavy bolt lift
119.5gr Loaded, but did not fire due to pressure at 118.5
Here are the groups - not that I was shooting for groups, but it's interesting to see. Of note, the lower end of the ladder felt like big heavy pillows pushing me back. At the higher end, it was hard recoil - and my shoulder started to hurt. I'm likely going to play in the 116 to 117 range.
Also note that this was a reused target - disregard the Shoot n' See targets on the lower left.
Here's the rifle:
