Well, I finally got it together!
Stimulated by a desire to shoot heavy boolits but finding stabilization of long heavy boolits a problem in my Marlin 1894 with 1:38 twist I decided to test same design different weight boolits.
So far my experiences with my gun, boolits and loads is in line with the Greenhills formula and I find boolits longer than about 0.75" do not stabilize well beyond 100 yards. In fact, anything much over 265 gr. groups poorly at 100 yards and many keyhole even if groups are good at 50 yards. I have tried lots of loads, different boolit designs and sizes to 0.435" and even "J" bullets - same result.
So I decided I would try some penetration tests to see if the heavier boolits penetrate significantly better than say a 265/270 gr. If so then I figured I might get the gun rebarreled or just buy a new one with the 1:20 twist Ballard rifling.
Anyway, after reading "Make Mine A .44" by Ashley Emmerson in Guns & AMMO last June I decided to do my own testing but from that article knew that the test media would be a problem. He was shooting through 38" of wet phone books!
I wanted to test at least 3 weights of same design boolit (240, 265 and 300 gr.) and at least 2 different designs so I would need at least 12 x 5 gallon buckets of wet phone books or newspaper with 2 end to end for each test. That is a pile of phone books and then they have to be disposed of after.
In the end to get things done and have a comparative test I decided I would use end grain birch to see what happened.
Informal and not entirely scientific but fun and informative, and I think worthwhile.
My conclusion from this so far is that I am happy with 265 gr. performance and will do some more testing.
I wrote this up in Notepad and attached it as a file to keep things simple. Click on it to open and stretch to get the table right (all in view) or unselect "wordwrap" - it should show up fine.