How do you tell if a Winchester model 100 rifle has had the firing pin upgraded?

The Winchester 100 has a recall in effect, and Winchester strongly recommends that you do not shoot your 100 until it has been repaired. The number to call to find out if your rifle has been repaired is 1-800-852-5734. Give them the serial number and they will tell you immediately whether it has been repaired by having the firing pin replaced.

If you shoot it without the pin replaced, the bolt may not close properly and it will shoot all 4 shots like a machine gun, or it can blow out the side of the receiver.