Bedding rifles for accuracy?

[czub]

It seems common knowledge that bedding a rifles receiver to the stock improves accuracy. Is it because it absorbs vibration from the hammer strike/firing pin/detonation because of more contact area? If yes, would a softer bedding compound or plastic shims work better?

[Jakeiscrazy]

My understanding is that it prevents the rifle from shifting in the stock after you fire a shot.

[Sideshow]

Your presumption about things wiggling an jiggling is largely correct. Accuracy in rifles is largely about precise tolerances. The tighter everything locks up shot-to-shot, the more likely the next bullet goes the same place as the last. Glass bedding rifles ensures a tight fit between receiver and stock. In wood stocks, it also helps reduce (but not eliminate) the affects of expansion and contraction due to changes in humidity.

Softer materials are generally a bad idea, even a Kevlar stock vs. a fiberglass stock doesn't work well. Lots of long range precision rifles are even built with aluminum "sleeves", basically a metal shoe that fits around the receiver, which, together with the receiver, get bedded into the stock. Welding accuracy "lugs" to receivers and pillar bedding are also common practice depending on the design of the rifle in question.

Along with bedding, ensuring that the barrel is "free floating" is also vital. This means you don't want anything pushing or pulling on the barrel at any time. Basically, the stock should never be in contact with the barrel, only the receiver.

[czub]

So you think there is a larger effect from things shifting from shot to shot and less from harmonics but both play a part?