I can confirm that a 3 1/2", 2 1/4 ounce load of No. 1 shot will do several things simultaneously.
1) Reduce a nice floaty crossing clay pigeon to its constituent molecules
2) Loosen your fillings
3) Cycle the gun so hard that the empties fly 15 feet
4) Cause a big grin on the lady shooting it!
(and the guys who had a couple as well)
It was a day for excesses. After blatting clays with those loads we did some target shooting with one ounce slug and then climbed back into my buddy's 7.3 litre car for the trip home (its some saloon car that can take 8 guns and ammunition etc in the boot)
A good day was had by all - and I did indeed pick up the empties of the Remington rifled slug and Mammoth magnum shotgun cases - they are all high brass and will make stunning match cases and a bit more interesting than the norm.