Have a little mystery I thought I'd throw out and see what opinions I get...   
The bullets were cast and lubed in the same settings (pan lubed and diameters are real close) the loading was done at the same time, virtually the same fit of bullet to lead, same crimp, (what little I use), same brass lot, most of the details as identical as I could get them.
What's a mystery is how does a 150 grain heavier bullet have a 100 fps faster MV with the same loading?  I ran the same loads through the LabRadar three different times with very similar data results.  I think I have a grip on the mystery and Pressure trace should confirm but other input is appreciated
Attached copies of the data taken
A hint here, the recoil from the heavier bullet is more 

Possibly a slight change in the pressure peak, area and rise.

I should have said too that a heavy bullet should also help with a more complete burn of the powder and higher velocity.

My belief is that IT IS due to a more complete burn of the powder with the heavier bullet.  The residual powder kernels that are common with 5744 were considerably less.   Pressure increase goes without saying.  Point of impact at the 100 yards where this was tested was within a minute of each on the vertical but with the wind the horizontal was almost 2 minutes different from each with the same sight setting.   Group size with both of these bullets were nearly identical, slightly over 1 moa centers with iron sights - (call me a wuss, but it does require some  determined focus to hold groups with this  ) 
Hope to spend some time at 400 and 800 this weekend and see how things compare then.
I did go back and check some load and radar data from last fall(it was in a file on my old computer, upgrades happened first of the year) - to get the same velocity with the 625's - everything else being the same my powder charge was higher by 1.5 grains.  Weird stuff happens when you start getting so organized you can't remember where you put things???? 
Thanks 
Greg

GT-I am watching your progress with your 50-90 with interest, I also have a 50-90 and shoot 5744 in it. Looking at your recent loads and comparing them with your target in the Sharps building post I see you show a load with the 785 grain in the older post with 25.7 grains, but in your recent post with chronograph data it shows 29.7 grains. Your 25.7 grain load is pretty light, I started a couple grains more and with heavy bullets it's plenty!

ndnchf wrote on Jun 2^nd, 2020 at 1:48pm:


Black powder burn is limited by pressure; smokeless rate of burn is accelerated by pressure.