I would have went with the 300. Just because of the bullet size. Should have looked a little closer at what you were shooting. But only 100 grains? Seems to be a little small. I would be afrad that the bullet would go right through the deer without expanding much.
I shoot a 25-06. During this time, I was using 100 gr. SP.: I have on a number of occasions shot a deer (knowing that I hit it) and went to look for a blood trail. NONE TO BE FOUND!!!! I spent about 2 hours walking around the Mt. that he ran up. Gave up and started heading back to my truck, when I found him. He died about 300 yards from POI. Not bad. But again, no blood anywhere around him. I now shoot the 117 gr. BT. And aim for more neck shots now.
They don't bleed out when you hit them with small bullets that don't mushroom very much.
Rereading your post, Seems ........ off....... +1.5 at 100 then -1.5 at 200?
I slapped this info in my range calculator:
With 66 grains of Powder. (Didn't pay too much attention in which powder)
I came up with a muzzle Velocity of aprox... 3222 fps.
This is what the calculator said at POA at 150 yards:
Damn. Cant copy/paste N.M. I guess your #'s are almost spot on with my puter.
I get 1.74 +/- at the 100 and 200
my mistake: Never played with a 257. I always thought they would be a bit flatter of a shooter.
Ok, the 300 on the other hand. Puter said that it would be -2.02 at 200 yds. if you POA is at 150. That was with a 168 gr. HP. Just in case you were wondering.
Totally up to you. I guess that 257 is much flatter then the 300. But the 300 is a bit bigger. Send me a PM. if you want me to look up different Drop rates for em......
If I were in your shoes, I would rerange em. Sight em in for 250 yds. or 300 yds. If all the deer that you saw were that far, good chance the next ones will be too.
Get a 44 mag in a holster for them little deer at 25 yds. then you should be covered. Good luck....