I've got a nice Marvel .22 conversion that I would like to use for Bulls eye. I've found a Nikon Monarch RDS for a decent price. Are these a good RDS? Nikon says parallax free at 50m. Have any of you used this sight on an AR .223? They are discontinued so don't want to drop the dough unless they are a good sight. I really couldn't find many reviews about them. Thanks so much.