Jim, I can make a somewhat educated guess on your bullet penetration results. The higher impact velocity (close range shot) caused the bullet to upset to it’s maximum diameter and perhaps (probably) lost more weight than did the longer distance shot.....hence the appearance of “less” penetration. JMO
There is also a “school of thought” in handgun hunting when using wide metplat handgun bullets.....penetration is somewhat lessened when impact velocities on flesh exceed 1200 or so fps using the same bullets from the same handgun. The theory being, the flt nosed bullet at the higher velocity displaces more tissue and the shockwave (my word) actually hinders penetration. Not saying less penetration....just not linear to the velocity increase! John Linebaugh of
https://www.johnlinebaughcustomsixguns.com/photos, has done a lot of research and experimentation on this subject.
I experienced the same thing when I went from my standard 375 H&H to mt 375 AI using the same bullets albeit 200 fps higher mv. In 1991, a bullet that I was very happy with, was a complete disappointment on a close range (high velocity) shot on an elk from the AI. A 270 grain bullet, broadside, behind the shoulder, only hitting a rib (and lungs) failed to exit. I
I expect more from my buleet from this cartridge. I immediately changed bullets , a 270 grain Barns (the original Barnes X) , and have only recovered 1 bullet. A stern to bow shot on a small bull elk..... a lot of ham muscle shattering the pelvis (I hit just to the left of my desired point of impact), a coule feet of gut, penetrated the diaphram, , left lung, exiting in the front leg pit, reentered the upper leg, reentered the upper leg, passing through the muscle (no bone contact), stopping under the hide on the offside of the leg! If you were counting, this was three (3) hide penetrations...... hide offers a great amount of resistance to bullet penetration! The recovered bullet weighed 257 grains....having broken off one “petal”! This is what I want and expect from a bullet......Barnes’ have been my only bullet since then, with no disappointments. My only changes have been changing bullets as Barnes improved their technology!
Though, I must confess that I dropped down to a lighter bullet (I hate light bullets), the 250 TTSX, for the much improved BC’s over the 270 grain TSX. I will go back up to the 270 LRX, when they become available and I used-up some of the 250’s! memtb