It is my understanding that the dimple was to enhance the liquid priming mixture to flow evenly (through capilarlary action) in the rim. I have heard that cases are spun to help deposit the priming mixture before drying. Priming is such a important part of rimfire accuacy, the powder charges are so small, the primer can contribute up to 30% of the propellant force. The amount and distrabution of priming mixture is the holy grail in accurate rimfire manufature.
Gort
Standard velocity 22lr ammo
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The priming mixture of all manufacturers has been spun on wet going back to the original .41 rimfires of the nineteenth century. I was told by someone involved in the negotiations between the Federal Cartridge Co. and the Soviet Union, to purchase a design license, that the dimple was meant to direct the primer flash forward across the top of the powder lying along the lower side of the case.
I think, regarding accuracy, that consistancy in the VOLUME of primer composition, is more important than consistancy of deposit, as it can vary the pressure curve, and if the cases are spun, the deposits should be uniform, with or without a dimple.
In Schuetzen Shooting, it is believed that the least important variable, regarding accuracy, is the powder charge, and the most time is spent with bullet uniformity, bullet position in the breech, and the best bullet lube for the gun. We even go so far as to use the same case over and over, and index it's position in the chamber with a file mark on the rim. While usually, bullets are weighed for unifomity, powder charges are just thrown with a measure, and not weighed.
Paul
I think, regarding accuracy, that consistancy in the VOLUME of primer composition, is more important than consistancy of deposit, as it can vary the pressure curve, and if the cases are spun, the deposits should be uniform, with or without a dimple.
In Schuetzen Shooting, it is believed that the least important variable, regarding accuracy, is the powder charge, and the most time is spent with bullet uniformity, bullet position in the breech, and the best bullet lube for the gun. We even go so far as to use the same case over and over, and index it's position in the chamber with a file mark on the rim. While usually, bullets are weighed for unifomity, powder charges are just thrown with a measure, and not weighed.
Paul