Washatonian
For the question asked and from the additional information that I know about you, your hunting conditions, and the fact that you have to use open sights and cap ignition. I really think that Builder is correct. I would see no reason to move from the 300 grain Deep Curl for those ranges. Also I know you really only want to shoot one weight bullet for both deer and elk. And again that falls right where you are with the 300 grain Deep Curl.
But, now in the same breath I would also suggest to you the the .451-300 grain Nosler partition PP has better Terminal Ballistics than a Deep Curl. It is also a stronger bullet and will be able to handle marginal shots into the kill zone somewhat better than the Deep Curl. One other thing the accuracy of the Nosler is not questioned by me. I shot the bullet years at elk here in Idaho for many years and I suggest to you that it is devastaing on game. As you know since we have shot together on different occasions I am now shooting a Lehigh/Bloodline and it took a lot of effort on my part to make that switch from Nosler, but I do feel it offers some additional factors that the Nosler, Speer, and Barnes do not. Please bear in mind all of this is just my opinion.
This is a recovered Nosler from an elk I shot a few years back... I have onlt recovered two Noslers from all the animlas that I shot with them this in 1 of 2...
This is the animal harvested....
Here are the aftermath pictures...
This guy did not like a Nosler either...
This might give you some indications also... Next time yopu get over this way we run out to the farm and shoot a few....