We achieved 3375f/s with the Lightning 12 slug (200 grains) loaded in 3" hulls in a Benelli Nova shotgun with 24" smoothbore barrel.
I read that shooters feel that a 338-378 WM rifle has a lot of kick. In a 7.7lbs shotgun kick is almost non existent even shooting off bench.

Lefteris
www.europeancartridgeunlimited.com