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Posted: 9/29/2013 4:10:57 AM EDT
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I was reviewing load data from Hodgdon's site for the 223 and for the first time I looked at load data for 90 grain bullets vs. 55 grain and compared powder charges for the same brand across bullet weights.
I get that larger bullets will likely have lower velocity, but is also that why the charges are so much smaller on the larger bullets? I would have thought a larger mass to propel would equal more propellant, but I am guessing that is over come by the need for lower velocity? Thanks |
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A heavier bullet needs a greater force to start it down the barrel so the pressure builds behind it for a longer time and this pressure causes the powder to burn more efficiently.
A lighter bullet starts down the barrel sooner and the pressure never builds as fast or as high. Some of this difference is due to the difference in the bullet mass and some of it is due to the heavier bullet being longer and having more surface in contact with the barrel . Lots of different factors and things going on when one drops the hammer . |
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Peak pressure is the constant and cannot be exceeded without nasty side effects. So if the bullet weight in a cartridge increases, the powder charge will have to decrease to keep the pressure constant. So the result is you can't push a heavy bullet as fast as a lighter bullet in the same cartridge.
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