bore the next time out. Removing every trace of moly is
unnecessary. Removing all metallic and carbon fouling is suffi cient. So long as the bore is oiled or greased properly for storage, remaining traces of moly are harmless. Proper bore cleaning after using
any gun is always an issue but this is particularly an issue for those who live in humid environments (especially humid environments where salt is also an issue, such as places near the ocean). When using moly-plated bullets proper bore cleaning and protection might be even more important. The combination of carbon, moly, copper alloy, and mois- ture on the steel can lead to microscopic etching. Any such bore damage might or might not degrade accuracy or sub- sequently increase fouling. The point of noting the potential
for bore etching is to emphasize that after firing any gun the bore should be properly cleaned and oiled before long-term storage. To me, it seems quite illogical that those who fail to follow this practice and who have been using moly- plated bullets would choose to blame moly for any subsequent barrel damage that might occur as a result of their not properly cleaning and protecting the bore. Upon what would they blame bore damage that resulted from not cleaning the bore of a gun from which they had been shooting only naked bullets? PROBLEMS RESULTING FROM NOT MAKING
NECESSARY LOAD ADJUSTMENTS Because properly moly-plated
bullets are so slick, when loaded into identically prepared cases and using the same propellant and charge and the same primer, typically, peak chamber pressure is signifi cantly lower. While this seems intuitively obvious to most shooters – less bullet-to-bore friction means the bullet will accelerate with less resistance, so peak chamber pres- sure will be less. However, the corre- sponding logical consequence, reduced velocity, is not so intuitively obvious. In fact, this result surprises many shooters. Nevertheless, as a bit of refl ection will clarify, all else being equal, if the load generates less pressure (force on base of bullet) it necessarily also generates less velocity. So, when we switch to moly-plated
bullets, to maintain accuracy (same bar- rel time), we also will need to increase the charge. This is a big issue, not be- cause of the modest velocity difference but because the change in barrel time that will occur if we do not increase the charge can alter what had been an extremely accurate load into a load that is useless for varminting. Barrel time does matter. Unless the original load was push-
ing pressure very close to maximum, the solution is to simply increase the charge until barrel time matches what it was when using naked bullets (this usually occurs when velocity and pressure are about 5 percent higher). Obviously, if the original load generated too close to maximum pressure, we will have to consider use of a different propellant (or other load changes) to achieve a
combination that gives accurate barrel time at acceptable pressure. A complicated problem that often
crops up when we begin using moly is that the primer blast moves the bullet before the charge ignites. Such primer- induced bullet movement is notoriously variable and is bound to destroy load accuracy. (We often get away with us- ing an unnecessarily hot primer with unplated bullets because those have enough friction in the case neck to stay in place when the primer shock wave hits. With properly moly-plated bullets, the primer blast is far more apt to dis- lodge the bullet because bullet-to-case friction is so much less.) The solution to this potential prob-
lem is twofold. First, where acceptable and possible, use a milder primer. If you already are using a rela-
tively mild primer, what do you do? The remaining mitigation is to ad- dress this basic problem by increas- ing bullet-to-neck tension. Generally, when using neck bushing dies, use a ¹⁄₁,000-inch smaller neck bushing. When using a conventional sizing die, reduce expander diameter about ¹⁄₁,000-inch. Sometimes, a greater increase in bullet- to-case interference can be helpful. Generally, the following load
modifi cations are necessary for good results when using moly-plated bullets: Increase charge (usually be-
tween about 3 percent and about 5 percent); Where feasible and appropriate, use a milder primer; and, Increase interference fit be-
tween bullet and neck (by ¹⁄₁,000-inch or more).
Of course, special situations occur.
Left, dedicated pan funnel and measure funnel. With these, I can easily achieve the higher charge density and superior packing scheme that swirl charging affords. Right, view showing technique and how this method causes granules to swirl into the case. My personal testing and additional testing I did both in the Norma ballistics lab and in the Oehler Research ballistics lab has proven that a uniform granule-packing scheme can signifi cantly improve ballistic uniformity. This works even with charges that fi ll only a small percentage of the boiler room and, once established, the packing scheme is very robust against handling.
Page 26 Spring 2012
I encountered a classic example when testing the 225 Winchester cartridge with the 40-grain BT. Both Varget and Rl 15 worked perfectly. A full case of either gave perfectly normal pressure, velocity was very impressive (partly because of the 28-inch Krieger barrel), and accu- racy was phenomenal. When I tested the same basic load using moly-plated bullets, velocity dropped about 75 fps and accuracy was no longer satisfactory. I could have used 4895 to get back to the same pressure and barrel time but I chose to use a swirl-charge, as necessary to get approximately 5 percent more propellant into the case. Velocity was higher than with the unplated bullets
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