Bigcountry, a lot of mass-produced injection molded stocks are not that stable. The plastics they use may not warp from fluctuations in humidity, but they can change due to fluctuations in temperatures. In addition, many of these stocks have forearms that provide no internal support, and can actually be squeezed into contact with the barrel. And Heaven forbid if you rest the stock on a hard object. They will bounce!

By all means, a high-quality synthetic stock (McMillan, Brown Precision) is a very stable stock. But not all synthetics are as good as these two.

Brian