I used to use a 20 ga shooting #4 shot for rabbits and squirrels and it was pretty effective. I'm sure you could do the same with a 12ga. Some folks might think that's a little too big, but the tradeoff is less pellets in the meat than with smaller shot.
You might check with the refuge to see if you have to use steel. At Gray Lodge you can use lead to hunt as long as you don't have waterfowl in your possesion, I know it doesn't make sense as you are hunting the same area as the waterfowl. Just thought I would mention that to save you a little money.
I used to use #6 when I hunted the flats east of Palmdale. But I switched to #4 in my 12 ga. when I started hunting cottontail around Cajon pass. I hunted by shooting from one side of a ravine to the other (up to 30 yards) with a super full choke, and I found that with the #4's, I could shoot right into the short sage brush that those little guys would stop behind. The #4's anchored them much more effectively than the #6's, so it was much easier for my dogs to find them in the steep, brushy stuff. I have to admit though, it was a tough choice when quail season opened up, so I carried a pouch of #4 and a pouch of #8 and took my chances when I reloaded and changed chokes, depending on whether I thought quail were in the area. I'm back to hunting open terrain in Mendota and the Southern Sierra foothils now so I use #7.5 and carry a few #4's, and change out my choke as necessary.
IN MY 12 GUAGE I KEEP A VARIETY. I GO WITH 6'S FOR SQUIRRELS AND RABBITS AND MOUNTAIN QUAIL.. BUT I ALSO GET RID OF MY OLD STEEL WICH ARE 4'S. I HAVE NEVER HAD A PROBLEM. I HAVE TRIED 7 1/2'S FOR QUAIL BUT NOT MUCH LUCK. THEY DON'T PATTERN WELL IN MY SHOTGUN.
Well I generally use the 7.5's because I am out quail hunting when I come across the bunnies. In most of the spots I go I am as likely to see quail as rabbits, and it would just make me mad if I was loaded wrong when I came up on a covey.
Its funny, but I see a whole lot more rabbits when I go out quail hunting because I think the dog scares them into motion, and the bunnies are focused on the dog and not me. I think the rabbits tend to hold alot tighter when I am by myself and I probably walk right by a bunch of them.
I think though that if I was just going out for rabbits I would have to take a .22
I would be interested in hunting with you Saturday morning as I live in VVille. PM me if your interested in a little company.
I'm getting to be a bigger and bigger fan of larger shot for just about everything. I normally look to #4s or #5s for the bunnies (jacks at least). This is from a guy who shoots quail with #6s though...
I generally use 4's (if for rabbits only) or 5 (if I can find them, my preference),
or if I can't get 5s and it is still also bird season, I use number 6 shot. Either in
20 guage or 12 guage. I find that fewer pellets in the meat, the better. Plus, the
larger (though fewer) pellets retain energy better at distance and also in those
cases where there might be a light screen of brush or foliage in the way at the
time the trigger is pulled.
In 12 gauge cottontails #8 or 7 1/2 low base, and for jacks if you want to be humane use #6 high base although 7 1/2 and 8 low base will stop them under a full bead but a tap-stick will normally be necessary. And the range will be limited.
Let them get out a little farther, and 6's are only use on jacks not cottontails. You'll waste the meat if you shoot to close. Be patient and let them get out farther. If you can't let them get out farther place the beed on the ears or skip shoot them by shooting a few feet in front of them. The gravel that a skip shot kicks up will stop a jack.
That's how you hand close shots with a shotgun. I've cut them in two at times on a jump shot at my feet.
My friends and I hunt cottontail over beagles in PA. I use an O/U 12 ga with IC and Mod chokes. I stick with #6 shot unless we might find grouse. Then my 1st barrel has #7 1/2 in it. I use 2 3/4" Remington game loads (low brass) unless there might be Pheasant around (not too many here anymore) then I fill both barrels with high brass and don't take close shots on rabbits. That's the beauty of using dogs. You can pick your shots more easily. Using the low brass, we end up with a lot of dead rabbits that we can't even find more than a bb or 2 in them. It doesn't take a whole lot to kill cottontails. I've got my eye on a 20 ga Red Label. I could still use it on the birds but I'll just carry some 3 inchers with me.