Okay, I am going to put this quite clearly, you may not agree, but these are my findings and are echoed by others using similar combinations of bullet and velocity:
The deer I have shot with copper at a variety of ranges 90% of them dropped on the spot, the others made it a maximum of 20 yards. They were heart shots that ran, and most heart shots do go bang flop.
In my experience with lead (mainly SSTs which people seem to rate highly), I probably got about 40-50% that ran 20 yards or more. They were not as effective from my experience, all these shots were with good hits inside a 'kill zone'.
I understand the point about a follow-up shot should a deer run and need another, however with the copper working well and myself having good accuracy from a variety of positions, I have never had a situation where I needed to take that sort of shot as my shots have been through an appropriate 'kill zone' and the bullets have done more than enough damage to drop the deer quickly, if not instantly. Follow-up shots should not be the sole reason for using one particular bullet, because if they are a regularity, you either need to question if you're shooting beyond your ability, or if the bullet is performing correctly. Equally you would have to question how far is the deer realistically going to run before running out of steam if it has been hit well, even if your shot is at 250m you do still have another 200m of range with certain combinations of copper (maybe further with others) I would expect to be able to get back on a deer and for it to slow to the point of being able to take a shot within that?
I agree that you lose velocity quicker using a light bullet, however all I am interested in is the ballistic chart - what range can I go out to, while maintaining at least 2200 FPS, which is where I believe the limit to for the TTSX, you may get away with slightly slower, but that is where I am comfortable to in .30 cal. By my charts produced on Applied Ballistics, trued with chrono data, I came up with the ranges stated in my previous post for my rifles.
Now while you may question the amount I have shot, the sample sizes for all my conclusions are large enough that I myself am very satisfied to draw my conclusion from them. I would not use non-lead if I did not believe myself that it wasn't the best tool for the task, on none of my stalking patches have I been forced to use non-lead, I do so by my own free will.
Ben