Stuart Otteson, The Bolt Action, pages 256-257 states,
"Both striker energy (1/2MV²) and impulse (MV) are functions of the mass and velocity of the firing pin, but with velocity more important in the energy term since it appears to the second power. If a firing pin is lightened, velocity will increase exactly enough to hold the energy term constant. Since impulse is only to the first power of velocity, however, it diminishes. Conversely, if the same impact energy is achieved with a heavier and slower-moving firing pin, a higher impulse effect results.
It might intuitively seem that impulse improves the detonation effect of the firing-pin blow, and thus for a given impact energy, the slower and heavier type striker blow is more effective. It also apparently follows that the lack of momentum in a light fast firing pin fall requires an increased energy to compensate.
Both SAAMI and U.S. Army studies on the subject show that exactly the opposite is true. At a given energy level, a light firing pin giving a snappy low-impulse blow is more effective in detonating the primer than a heavier and slower pin. A sharp, high-velocity impact transfers its energy to the primer faster and thus at a higher peak level. The low-velocity impact, with its greater impulse, not only transfers the energy over a longer time period, and so lower peak level, but it allows more cushioning in the energy-transfer process. This was graphically illustrated in extensive development work at Olin Corporation and described in U.S. Patent 3,056,226 of Oct. 2, 1962 (Charles Hubbard and Robert Smith).
The above explains a more subtle relationship between striker design and lock time. By only increasing mainspring power, and retaining a heavy firing pin, a slow-velocity/high-impulse ignition results. By decreasing weight, the percussion becomes a high-velocity/low-impulse type. This allows designing to a somewhat lower energy, thus making possible a slight additional lock-time gain.
Another practical advantage of a light, high-velocity mechanism, is that it allows ignition with a less violent striker blow. Since the jar of the striker blow precedes the bullet to the muzzle, this enhances a rifle’s potential accuracy.
Just how much impact is actually necessary for primer detonation depends also on a number of other variables. Certain standards are available, however, which consider normal manufacturing tolerances and necessary margin for reliable ignition under varying conditions. Current U.S. Army sensitivity requirements are 48 in.-oz. for small-rifle primers and 64 in.-oz. for large-rifle primers.
Most commercial arms today use the same firing pin assembly for both primer sizes. One of the largest firearms companies bases their designs on large-rifle tests which established the following necessary impact levels for perfect ignition: 30 in.-oz. for a clamped primer, 40 in.-oz. for an ideal firearm, and 63 in.-oz. for an average production firearm, they have chosen 75 in.-oz. as the goal for their production centerfire rifles by taking the ideal firearm 40 in.-oz. figure and 10 in.-oz. for the maximum anticipated firing pin eccentricity (off-center blow), 10 in.-oz. for the maximum anticipated headspace variation (cushioned blow), and 15 in.-oz. for the effect of extreme temperatures."
HPC
Different helix angles can cause coil stacking...bad ignition juju that is difficult to track down.