You're quite welcome, Nuts. A couple things...
First, a 7 1/4 lb shotgun(Probably heavier than your 500) firing a 1 1/4 oz Brenneke slug has about the same free recoil as a 9 lb 375 H&H firing the usual 275 gr load.
IIRC, the last '06 I had packed about 30 ft/lbs of free recoil with its 9 lbs loaded weight and 165gr bullet.
That 12 will go maybe 50 lbs, tho my math or memory may be off a tad.
And few riflemen stand there and shoot off 250 rounds a day like some trap,skeet and SC fanatics do. Kick is cumulative.
Don't let this throw you. With good instruction, most folks willing to learn can fire shotguns amazingly well.
And the lack of good instruction is why there's so many folks who do not shoot their shotguns well, or even at all.
If there's questions, sing out, we've got a very good bunch here to answer them....