I use a lead sled for target with my 300 wsm. I do not put weights on it nor tie it down. I like it to slide some. I have figured out that to get the hairs on sight one puts pressure on the stock. That pressure I believe causes the rifle not to shoot the same depending on how much pressure is applied. Now I take lots of time to adjust so that I am putting little to no pressure on the stock. Works for me.
Pressure on the stock - I had read about the very precise hand held bench rest guns - so typically smaller cartridge - like .224" or 6mm caliber - heavy rifles, like 12 or 15 pounds (?) - shooter makes about NO contact with the rifle - is held aligned only by the supports - is free to recoil upon firing - the exact same every time - had read one shooter (Speedy Gonzales ?) say that he wanted to match his finger print where he touched the trigger - the ONLY contact he made with that rifle upon firing. These are the guys shooting "two's" and "teens" (.2xx", .1xx") 5 and 10 shot groups at 100 yards.
Is about very little to do with "sighting in" a hunting rifle. My experience is that the hunting rifle is firmly gripped with shooting hand and on the forearm, firmly into shoulder, head down fairly secure to comb - when firing at deer. So, I think, that is what you want to reproduce, when you are "sighting in" - grasping it / supporting it, as similar as you can reproduce, when you will be firing at game.
I don't think that "world class" high end shooters use rests at all to "sight in". These are the guys who practice trigger break - dry firing - with a coin balanced on end on their front sight or on scope turret - coin does not fall over when they trip the trigger. With laser pointers, can see they can hold very tight on a target when trigger breaks - like parts of MOA sighting error. They are good enough, they adjust sights to hit what they want, by shooting, as they would for score. Us mortals have to use some kind of rest or support, to calm down the wiggling enough, to be satisfied that our sights or scope is actually aligned where the bullet will go. And, I am quite convinced that the bullet goes to a different place, depending how the rifle is supported.
Do not loose track that the kill zone on a broad side whitetail deer is about 12" or so. A bullet through any part of that results in a dead deer. So if you can put 5 out of 5 shots into 4 inches at 100 yards, you are good for 90% or more of the deer that I have taken or seen taken. From multiple target shooters, I have been assured that if you think you might want to pull off a 400 yard shot, you have to actually shoot targets at 400 yards. What you got on 100 yard targets, may or may not have much to do with your results way down range. My brother tells me that he and his hunting partner - both with 300 Win Mag, 180 grain - well sighted in at 100 yard range off of sandbags and shooting tables - multiple times have missed 600 yard 4 foot x 8 foot plywood from field positions - they simply were not prepared for the windage requirement, way out there, besides the drop.
