Notes: As you can see I only had one load that made Major PF and then just! I picked a COL of 1.170 to keep pressure down and it seemed to be a common / popular choice but I found that it was just a bit too long to fit in my STI mags with 9mm spacers.
From here I'll try the Ramshot Silhouette at shorter COL's (I've seen several references for this powder / bullet combo at shorter COL's) before I go to a higher charge weight, as I find 8gr is nearly a compressed load.
Overall, compared to results posted here I seemed to be getting ~2.5% - 3.0% lower velocites with the Silhouette and ~6% lower with Autocomp. At first I thought my chrono was mis-calibrated but due to different deltas from the reported data I don't think so. But I could be wrong.
Also, the previous pistol owner told me 8.0 gr of Silhouette gave him 170PF. I think he said COL was 1.170.
Any other thoughts?
Note the part I put in bold....it doesn't work that way. If you increase the OAL, it will lower the pressure and lower the velocity. That means you'll simply need more powder to increase the pressure and velocity to the desired level.
There just isn't a free lunch where you can increase the OAL and keep the same velocity, but get lower pressures. Set the OAL at what fits in your mags and what runs in the gun, then adjust the powder charge to get the velocity you want. In the end, shorter OAL, longer OAL, more powder, less powder, it's still going to take the same amount of pressure to drive the bullet to the target velocity.
People will often bring up different pressure curves when talking about varying OAL, and that can be true, but almost any change we make also changes the pressure curve, to some degree or another, but it's not going to make a significant change in peak pressure, which is what we're concerned with.
If you're using a different lot of powder (likely) than the original owner, and sometimes even a different lot of the same bullet, you're likely going to see a difference in velocity. On top of that, no two chronos are the same, and environmental conditions are rarely identical. Throw in the fact that many people do very limited chrono testing and call it good...i.e. they run five rounds over the chrono, got 170PF and they stick to that load for a long time without ever checking it again. Add all of those things up and there really isn't any way to tell if what you're seeing is different from what the original owner was getting. R,