Terry,
I have a Tikka Stainless Synthetic and it too is made out of polypropylene. This is a special material that is extremely durable. In fact, there is a boat company that makes boats entirely out of this material.
My Tikka Synthetic stock is much more durable and solid than my cheap plastic stocks on my Remingtons. The Winchester stocks are better than the Remington stocks, but not as good as the Tikka stocks.
Now, I would not rate the Tikka stocks as good as the HS Precision or McMillan stocks, but, again, they are much better than the Remchesters.
Zachary