Since this seems to be a topic for everyone to toss their $.02 in for free................ here's wharer I'd go on you budget:
I'd do some looking around til I found a NICE used Superposed Lightning 20 ga. and POUNCE ON IT .
Gotta agree with Mr. Battue that, on grouse at typical grouse ranges under typical grouse conditions, the 12 will be of very slight advantage in pellet count over smaller bores. The added weight of the 12 will over-shadow any advantage it gains in payload.
