Bullet weight

H

Hog head

New member
I fell into such a deal on some reloading supplies recently that I bought a rifle to use them in. The problem is the bullets seem to be odd sized.152 gr for example. How do I deal with this, round up,round down to fit my data? If you can round one way or the other how much do I drop the powder charge to start with without going too low? I'm loading for a dpms lr.308 if that matters.
 
Up to a three grain difference can usually be ignored. That's a normal spread for many cast bullet multiple cavity molds. It's also the normal specification for .30 cal military bullets (M2 Ball bullet 152 grains -3 grains tolerance; M1 Ball 174.5 grains -3 grains tolerance). You only have a 2 grain difference. Much more important is the construction (cast, copper cup and lead core jacketed bullet, copper solid, etc.) Just take the nearest weight load data you can find. Preferably the next larger weight, so a 155 grain bullet's data in the case of the 152, and go to its starting load and work up while watching for any pressure signs.
 
is the difference in flat base and boat tail so easily ignored. I see some of the same weights but with diffrent bases. All the bullets are jacketed some flat based others boat tailed some with lead showing at the base.
 
Bullet jacket hardness and diameter across those of near equal weight easily cause a greater peak pressure range than 10 grains of bullet weight. I got a bit flatter primers with .3092" 185 grain Lapua bullets than .3082" 190 Sierras with the same component suite in the same barrel. Same thing with 168 grain Sierras and 170 grain Lapuas; same brand diameters, barrel, case and primer but one more grain of powder.
 
"...152 gr, for example..." Use 150 grain data. 2 grains will not matter. Ditto for daft stuff like Hornady's 178 A-Max. Either 175 or 180 grain data will do. Close counts.
 
Note that Sierra and Hornady data tends to be conservative, so they have even more room for bullet weight variation than, say, Hodgdon data does. Some bullets are longer than others of the same weight and that causes pressure to shift some.

Bart is right on about bullet composition and shape details. In the 70's, NRA's Wm. C. Davis, Jr. got 7,390 CUP difference just from exchanging different cup and core flat base 150 grain bullets. His loads ran 44,510 CUP to 51,900 CUP.
 
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