Sporting Mauser's don't need a steel lug in the stock.
In the old days, the gunsmith just did a good job of inletting the receiver's recoil lug to the stock for a perfect fit.
The reason the military rifles used a steel lug was because it was faster to get a tight fit and added strength.
Today, we use glass bedding compound, sometimes mixed with powdered metal for added impact resistance for Magnum rifles.
The truth is, the glass bedding is stronger than the old steel lug because the glass bedding compound spreads the recoil over a much wider area.
You will see cracks around steel lugs on old military rifles. You don't see cracks in glass bedded rifles.
I suggest doing some reading on glass bedding a rifle and the correct method of doing it.