What would you recommend I zero this sig copper head with holoson 512 red dot?

I'm just not sure if this should be zeroed like a handgun or a rifle?

Thank you

20 yards.
Barrel is handgun length.

25yds if you want the same POA/POI as a handgun.  The fact remains that you’re still dealing with a handgun round, and if you zero it for anything beyond 30yds, your bullet is going to climb above the POA to the point where you will have to hold low at specific intermediate ranges, versus holding dead on, or high.  

50yds is doable because the highest a 115gr bullet will go above the POA is about 0.25”, which is negligible.  I don’t recommend anything beyond 50yds.

I zeroed at 15 yards for my 8” Cmmg upper. It makes hit to 125
yards with ease.

I would be tempted to run it more like a pistol so 20-25 yard zero (depending on weight of round 115-147) and barrel length also.

10 yard "zero"