I use and like the lead sled #2 for it's adjustability. I also use it to remotely test fire newly built rifles.
Also I never add weight because it doesn't need it. (It weighs around 18 pounds). and it doesn't restrict the normal movement of the rifle.
I also use it for precision accuracy testing because it locates the front rest in the exact same spot every time. One of the main causes of inaccuracy, is changing the front rest location slightly while shooting. Once the accuracy load is found, then I will switch to sand bags or similar rest that will be used in the field. For finding the exact zero I want for hunting.
Bipods are another good rest If you hunt off the ground, but you need to practice and become proficient and consistent at using them. They also locate the front rest in the same location every time. Just like almost everything else in this sport, there is no one rest/thing that is best for everything and every situation.
The lead sleds have their place, and do what they were designed to if used properly. Rail guns use this system for ultimate accuracy and they will weigh many more times than a lead sled, They don't need a stock so the weight doesn't matter like adding 25 +pounds to the sled does. the only time I add weight to the sled is when doing slow motion Videos of rifle reactions to recoil and only enough to hold the rifle in a static position. On a few occasions, the test was discontinued to protect the stock.
I think it is a good tool if used properly and for certain reasons.
J E CUSTOM