Used UDs on numerous guns including slide mount .45 ACP.
For a .243 you might look at illuminated reticle scopes but for a pure 1x red dot UD cannot be beat. Watch the dot size; 4 MOA blots out 4" on your deer at 100 yards. They make a 4 dot size UD version, believe smallest is 2 MOA. Also have models with crosshairs etc. if not mistaken.
I have an Ultra Dot on a Ruger Redhawk and it has been really good. The Sightron looks like it would be just fine too and has a Lifetime warranty.
If going with Ultradot I would probably go with the Match Dot as it has different size MOA dots and on a longer range pistol you want a pretty small dot. I would not want larger than 3 and 2 would be better.