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Old 09-03-2014, 08:32 AM
edlmann edlmann is offline
Join Date: Oct 2009
Location: lovely downtown Central Florida
Posts: 5,071

Originally Posted by sigman2 View Post
Even though this ammo is HXP 1978 they could be from different lots. The powder burning rate will vary from lot to lot so the charge weights will vary accordingly. There will always be very minor variations in the powder charge of ammo from the same lot. The powder charges are measured by volume, not individually weighed. The 53.6 to 58.4 gr. charge shows that these are from different lots. If you take ten rounds from ten different lots and adjust the powder charge to the same weight you will have a real mixed bag of loads. Remember there were usually multiple lots run in the same year. Head stamp year does not mean the ammo is the same as far as charge weights. You need to separate your ammo by lot numbers which is not possible with loose ammo. This is why I prefer not to buy loose ammo.
Good reason for the variation in charges: on the production line, manufacturers use powder which is NOT conformed in its characteristics as is the powder you buy with which to reload. Rather, the loaders test the lots and adjust the charges accordingly to fit the burning characteristics of the powder in the lot they received - not a uniform standard.

ETA: There is some value to breaking the asphalt bond by seating the bullet very slightly. This would theoretically help uniform the resistance. Dunno if I'd then shoot the ammo in a Garand - might want to experiment with a bolt gun.
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Last edited by edlmann; 09-03-2014 at 08:36 AM.
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