Trying to figure out the setup for turkey.  I currently use a moss berg 500 with a fixed full choke 28” barrel.  It works nice for me, but I want to put a red dot on it.  
When not used for turkey I put a 18.5” HD barrel on it.

Wondering how much of a difference it would make with regards to the HD barrel.

Would the shift of impact be massive between two barrels?   At a home defense range?  
Obviously I would try it and see where it hits, just curious what the hive has seen. I might just bite the bullet and get me a new shotgun.  

Thanks.

I figured that.  Was just curious about others experiences with it.

Others experiences will be that you're going to have to pattern both.

My shotguns will sometimes exhibit significant differences in POI with different loads out of the same barrel. The only way to know how both barrels will pattern on your gun with your loads will be to personally test them.

Will you see a significant change in POI? Maybe.

Will they both hit to the same POI? Also maybe.

Will the difference be "massive"? Probably not (if by "massive", you mean a couple of feet of difference)