Re: Remington 5r at 1000 yards
Seeing that you are probably shooting in NC, you are most likely shooting near sea level, higher than standard temperature for most of the year, and in high humidity.
The higher than standard temperature and high relative humidity should give your ballistics a slight nudge; however, being close to sea level (Raleigh is approximately 400 to 500 feet ASL), you are shooting in denser air.
I ran a quick comparison of SMK 175 (what I use in VA) against SMK 180 and got what I expected. You are going to see slightly less drop with the 175. The energy is slightly less on the 175 and the flight time is almost identical.
I'm finding that the 5R rifling in the milspec barrel loves the SMK 175 at sea level and is most noticeable beyond 500 yards. Inside 500 yards at low altitude and all other things constant, the 168, 175, and 180 all produce about the same results. When I hunt with it, I use Barnes TS 168 and use my SMK 175 dopes out to 300 yards.
But, to throw my answer at your question; stick with the SMK 175's or hand loads of the same recipe.