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For a time they used ground glass in primers. I don't remember when they stopped, but it was due to barrel throat errosion. So, if a report from yesteryear happened to use those primers, it wouldnt be accurate with today's primers. Does anyone know when the priming mix using glass went out of favor?
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One of the theories on barrel wear is based on amount of powder, haeat and pressure. A certain caliber barrel will be worn out by a certain amount of powder. In theory, a 30 cal shooting using 40 grains of powder will last twice as long as a .30 using 80 grains - 308 and 300 Win Mag come close in this respect. Bullet fit anf hardness can affect heating and pressure, bullet friction has more to heating a barrel than that hot powder charge. The barrel steel has internal friction from flexing due to bullet passage, swelling like a snake swallowing an egg as the bullet passes through along with actual lead or copper on steel friction. The softer lead bullets and the lower charges used by MOST boolit shooters lengthen barrel life by burning less steel AND creating less heat friction in the barrel. It would take hundreds of barrels, tens of thousands of rounds in very controlled conditions to actually create a scientific finding. Generally what we know, lighter powder charges, softer bullets make a barrel's accuracy life longer. Only you can determine when a barrel is too worn to meet your requirements. last longer