On my Sporting Browning O/U's the main differences from the field Citori's is:
- The rib of the gun is higher and tapered. The taper in theory is to draw the eye to the target. A wider rib is all about the sighting plane for the eye to focus with the target alignment. Have two different barrels for the one gun which is versatile and allows me to shoot all the games with the high rib used for trap. One gun with 30" barrels and the other with 28" so it's a versatile set up for me.
- As you mention, barrel porting.
- A mid rib bead is more common on a sporting gun.
- Triple trigger feature which allows the user to change the style of trigger and some adjustment in the length of reach to the trigger.
- Probably biggest difference in field and sporting guns is in the stock. My Special Sporting stock falls half way between a field and a trap stock in height of the comb which fits me very well. Again some sporting guns have an adjustable comb that allows custom fit to the user .
- Many sporting guns have a more pronounced pistol type grip for target use. Mine has the right hand palm swell which again is a nice feature.
- Sporting guns generally have a different style recoil pad designed so it won't snag on clothing when the gun is being mounted.
- This picture may help. Don't own the field Citori in the center any longer and have replaced that with the 28" barreled Special Sporting. The top gun was my first venture into O'U's and bought that one new in 1998. Started out as a Lightning Sporting but changed out the stock and added a second barrel. You can see the differences as mentioned above.
- The bottom one being one of my favorites. Browning 325, 20 gauge. Chokes opened up to IC.