I happen to have a (signed) copy of Hatcher's Notebook. (I found out after my dads death he was buddies with J. Hatcher!) On page 398 mention is made of Mr. Garand designing and building a faster firing pin. It was alleged to cut the lock time from a service/standard firing pin (.0057 of a second) and a National Match pin (.0049 of a second) down to .0022 of a second. There is/was also a special firing pin spring needed. It was described as some type of special chrome vanadium metal that had a square cross section rather than round as most other springs. (There is a picture on page 397 of a standard and the modified firing pin.)
That, according to the numbers, would be a big difference in lock times. However in real life, I don't know if the squeeze would be worth the juice.