I've got a Kodiak .50 cal. that I last hunted with 15 years ago. I've gone through it putting in new firing pin, firing pin spring and breech plug.

When I hunted with it I used Power Belt Platinum 270gr. bullets. In all honesty I had no complaints. I'm looking to change bullets. I've got Hornady .451 cal. 250gr. XTP and Hornady .458 300gr. HP. I've got Harvester sabots. I will be using Shooters World .50 cal. pellets @ 100gr. charge. My max range where I'm hunting will be about 125 yards.

My main question to those who have used either of these bullets is; will the lighter bullet @ 1800 fps be tough enough for close shots and would the heavier bullet @ 1700 fps be too tough at the max range.

I run 250 gr TEZ with Blackhorn in my Kodiak but have heard good things about the XTP's

For deer? The 250 will be fine. So will the 300, if it stabilizes. You will get more pass throughs with the 300. At 125 yards I don't think there would be more than about an inch and a half difference in elevation, but it may be off to one side . Personally, I'd use the 250. I have shot many, many deer with 240 and 250 XTP's. Reliable and accurate.

I've used XTP's for 20 years and haven't lost a deer yet. I think mine are 240 though

Yes

240 vs 250 gr will have no difference