A while back I purchased a Sig p320-x full size with a Romeo Pro red dot and suppressor sights. I finally got a chance to test the red dot out. The red dot was co-witness and I assumed all was good to go. I decided to give three rounds using the iron sights. I aligned all three dots and all three rounds hit four inched below the center. I loaded up another three rounds and all three rounds four inches below center. At first, I thought it was me. I bench rested the pistol and same outcome. I then aimed four inches above the center and hit dead center. I noticed a little shelf on the front sight and when I line that up with the two dots dead center, but the front dot is way up in the air. I then tried the red dot and sure as heck the rounds all hit low, I raised the red dot up and its actually under the front dot and dead center shots. I am confused on what to do next. I have never had anything like this happen.

You 'might' be doing it wrong. The Sights on SIG Pistols are set up for a 'Combat Hold' sight picture. Which one are you using?



You don't indicate the distance to the target, but if you're NOT using version 'III' in the graphic above, that 'could' be your problem.

. I also contacted SIG and they said the pistol should have a #8 rear and #8 front. It's definitely a #8 rear and there is definitely #6 front. I don't know if this changes things. If all three dot are aligned and you aim dead center all hits are below the center.

Front sight #6 is 0.230" tall.
Front sight #8 is 0.220" tall.

If it's #6 when it should be #8, then it will cause you to hit low. It sounds as if someone installed the wrong sight height during assembly. You should take a photo and email it to Sig. They will probably send you a shipping label and have you ship the slide back to them for replacement sight installation.