The problem is that the OAL will vary between manufacturers, type of bullet, and even lots. Not to mention every round will have a slightly different OAL due to the way they're loaded. There just isn't a way to accurately gauge them after any kind of setback, you need the OAL from before you suspect setback.
Here's a toast to our wives and to the women we loved. <pause> May they never meet.
The M1 Garand rifle is the best battle implement ever devised by man.