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I've oft wondered how the same powders,primers,bullets weight come to be changed from,1 yrs manual to anothers.I have Phil Sharpes original book on handloading(autographed)up to the new Lyman.What's changed that makes powder weights gone down(mostly)??It would seem the steel/alloy used for a modern modern firearm would be stronger??Eternal questions...
 

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Charges have gone down due to the way they measure the pressure. Older manuals had pressure check via a "copper crusher" or CUP measurement. This pressure was measured based on how much a copper pellet was "crushed". Newer, much more accurate methods of measure have been used over the last 10-15 years. It is an electronic measure and quite accurate. ALSO, pressure measurements will vary from one company to the next because they each use their own test barrels. If one company's barrel is .0001" smaller,(tighter!) that pressure is going to be HIGHER and vice-versa. Also, I have my suspicion that company lawyers are in the equation somewhere. Older manuals will generally have larger powder charges for a given bullet. Sometimes, dramatically so!
 

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Charges have gone down due to the way they measure the pressure. Older manuals had pressure check via a "copper crusher" or CUP measurement. This pressure was measured based on how much a copper pellet was "crushed". Newer, much more accurate methods of measure have been used over the last 10-15 years. It is an electronic measure and quite accurate. ALSO, pressure measurements will vary from one company to the next because they each use their own test barrels. If one company's barrel is .0001" smaller,(tighter!) that pressure is going to be HIGHER and vice-versa. Also, I have my suspicion that company lawyers are in the equation somewhere. Older manuals will generally have larger powder charges for a given bullet. Sometimes, dramatically so!
Well stated!
 

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The crusher test method for pressure measurement is kind of a summation of the all the pressure over time in one simple measurement.

The new electronic measurement use a pressure transducer and an Oscilloscope so the shape of the pressure curve can be seen instant by instant in time. Sometimes that reveals peeks and valley in the curve that could be a problem for a real gun and the engineers drop the load until those abnormalities disappear.

Also in those very old manuals they might not even have used the crusher testing and just went by seat of the pants indicators, like condition of the fired primer, measurements of the case just in front of the rim, or velocity increase per step changes in the powder charge. All these are really too crude and real pressure testing with the electronics is really required. It is important to use the very latest reloading data not data developed decades ago or ever years earlier.

Hot charges are very over rated but that use to be a contest between buddies and reloading manuals (sometimes). The best accuracy is rarely at the limit of powder load as the accomplishment of accuracy is a very complex thing having mostly to due with the wiping of the barrel and a bunch of other little things that all add up. The trick is to get the bullet to leave the gun as the wiping changes direction (its extreme travel) as it has to stop to change direction. Shooters looking for accuracy vary the velocity to get the bullet to leave the barrel at that point. Rarely if ever is that at the hot end of the velocity spectrum.

LDBennett
 
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