For those who are interested (both of you!), here's how I derived the equation that I posted:
Eq 1: (K)inetic energy = 1/2 * (m)ass * (v)elocity^2
We can measure the mass of the striker (firing pin) and spring (as it turns out, that won't be necessary), but there's no easy way to measure the velocity, so we have to calculate v somehow.
Since the striker accelerates from a stop (cocked position), we could calculate the velocity at the end of its travel if we knew the acceleration of striker and the time that it takes to travel from the cocked position to the fired position (lock time). Eq 2: v = (a)cceleration * (t)ime
The acceleration of the striker can be calculated using Newton's second law of motion, Eq 3: (F)orce = m * a. Rearranging, Eq 4: a = F/m. We know the force on the striker because the spring force is generally given in pounds in the cocked position. For long springs and short firing pin falls we can assume that the force is constant over the firing pin fall. Though not quite true, it's close enough.
So, substituting from Eq 4 into Eq2 to calculate v, Eq 5: v = F/m * t
Now, how do we calculate t (lock time)? The (d)istance covered by an object under constant acceleration (produced by a constant spring force, in this case): Eq 6: d = 1/2 * a * t^2. Solving for t: Eq 7: t = sqrt (2d/a). Again following Newton's second law of motion, substitute F/m for a, so that Eq 8: t = sqrt(2dm/F).
Substituting from Eq 8 into Eq 5, Eq 9: v = F/m * sqrt(2dm/F)
As a reminder, Eq 1: K = 1/2 * m * v^2
Substituting v from Eq 9 into Eq 1, K = 1/2 * m * [F/m * sqrt(2dm/F)]^2
= 1/2 * m * F^2/m^2 * 2dm/F
= F * d
So, if you know the spring force at its working length, and assume that it doesn't change (much) over the short firing pin fall, and you know the distance of the firing pin fall (about 0.200" in a Rem 700), you can easily calculate the kinetic energy of the striker at impact.
However, I wonder along with Butch -- why would you want to know?