All you have to do is to look down the clean bores from the breech end.
If the "rings" the shadow from the chokes are not concentric are not concentric the barrels are not straight.
Now, I actually heard this at a Provincial Trapshoot re bending a barrel:
"Place a bag of shot on a picnic table. # 7 1/2 works best. Remove the barrel from the gun. Take the barrel in the hand and raise up high, and bring down smartly on the bag of shot, bearing in mind the new direction you want the shot pattern to go"
In this case I think the comb needs raising, unless you or someone else, drove a vehicle over it, don't laugh, ask me how I know!
