c-g-designs

LOCKTIMES:

The chapter hereunder is an extract frpm the magistral Stuart Ottespn’s book. It goes against received ideas, but ir reflects so well the reality that it greatly inspired me for the C.G furing system. Thank you Stu..(We met in 1993 and I detailed him the C.G firing system whp impressed him.

From Stuart Otteson's book The Bolt Action’ (1976), p. 256: 

          "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 US 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 US 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 low-velocity/high impulse ignition results. By decreasing weight, the percussion becomes a high-energy/low impulse type. This allows designing to a somewhat lower energy level, thus making possible a slight 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 a necessary margin for reliable ignition under varying conditions. Current US Army sensitivity requirements are 48 inch-ounces (0,34N/metre) for small-rifle primers and 64 inch-ounces (0,45 N/metre) for large-rifle primers.".

Note:

For a C.G 4mm FP travel,this results in :

 = 85 and 112 Newton respectively.