Dunk; I use both in my 6.5mm rifles, but have found little need for the heavier bullet for deer.
The 125 shoots a bit flatter. [3050+ fps vs 2750+]
I have yet to recover a 125P from a deer, after shooting about 25 with this bullet.
I feel that if these are not staying inside, why go to a heavier bullet?
I do have a recovered 125P in my collection, but it came out of a moose, not a deer.
While I do not necessarily go moose hunting with the 6.5 and the 125P,
In this case it was opportunity that presented itself.
I was deer hunting, and an immature Bull Moose showed up unexpectedly.
I gave him one in the ribs at about 200 yards.
He dropped in about 10 seconds right where he stood.
Bullet was under the skin on the offside.
I had an interesting experience many years ago with a 6.5x55 and the 140P
I had a doe draw, and was hunting with two companions with the same tags.
5 does crossed in front of me about 120 yards away, ran up the hill and over a
little ridge, out of sight.
One doe then returned, and stood on the ridge. She was about 200 yards away.
I up with the 6.5 and gave her one through the lungs.
She dutifully dropped right there. I wandered up to dress her.
Imagine my surprise to find a second doe down behind her with a broken back, hit just above the shoulders!
That 140 had killed two deer, not one. I never saw the second deer until I walked up that hill.
Penetration of the 140 is surely NOT in question, lol.
Regards, Eagleye.