I experimented a while ago when my wife first got her synthetic 700 in 300WM. Bought some devcon and filled the entire stock from front to tang. Essentially this made the stock so stiff it was practically an aluminum bat wrapped in plastic. So to answer your question, it did squeeze accuracy out...
What about the new information released with the current Prescisionrifleblog research? According to the test on some high scopes, the 5-25x56 S&B is coming up SHORT on high magnification. If this is true than users are getting a 7-22.4 zoom out of the S&B. Link below explains the results and...
Just started loading 300 wm myself. From what I've read on the forums, Norma seems to be the best as it is my understanding that Lapua doesn't and hasn't made 300 wm brass. Also I shop on precisionreloading.com