Re: Caldwell Lead Sled...
I have the Caldwell "Solo" model along with a caldwell bag filled with lead shot.
If you are shooting a "kicker" you'll appreciate it if you are spending time at the range testing loads. Went with the solo because it will accept AR type weapons with long mags, as well as bolt guns. Putting a 25 lb. bag of shot on it really dampens the recoil. Add another bag, or a couple 10 lb. weight plates and you can really reduce felt recoil if you have a gun that kicks like a mule.
The solo will also do double duty for holding a rifle for mounting a scope.
Watch Cabela's - they are on sale often.
Can't say much more as far as a review. It works well if you have enough weight for the gun you are shooting. It's not overly heavy to carry, and is easy to adjust. Some of the other models have a few more "bells and whistles". If you are shooting one of the larger calibers mostly, you might want to consider a heavier, beefier model.
Although lead shot isn't cheap these days, I'd recommend buying lead shot and put the bags into a caldwell weight bag. You can use sand or whatever you like, but lead being dense give you more weight in a bag vs. sand or something else. 2 bags of lead shot, plus 2 caldwell bags will probably cost as much as the sled itself. You can also use old lead wheel weights if you have a place to get them and make your own bag out of balistic nylon or an old jeans pants leg.