Jimro, weak firing pin springs don't detonate the primer compound as uniformly as strong ones do. Primers are much more uniform when they're smacked very hard and deep by the firing pin. Non uniform primer firing causes a greater muzzle velocity spread. And this is the reason why folks shooting competition at the longer ranges change springs often.
A 32-pound standard Rem. 700 firing pin that's weakened by 25% will have its normal 2.6 millisecond lock time increased to about 3.2 milliseconds. That's only about a 0.6 millisecond increase.
Win. 70's lock time with their 23 pound standard spring's about 3 milliseconds. I use 26 or 28 pound ones in my Winnies.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master