Just curious, in your opinion, is it better to carry heavier grain bullet or lighter bullet for self defense carry weapon. I have a 40 cal beretta, which I don't have any self defense ammo for and want to purchase some. I know there is some that like the heavier bullets and some that like the lighter bullets. I was just wondering what your reasons are for carrying lighter or heavier bullets. I was personally considering the Speer Gold hollow points in 165 grain for my 40 cal. Thanks for your opinion and information.
Putting aside for the time being, the issue of shot placement, I tend to go with bullets of high sectional density because sectional density (along with velocity, of course) is what drives expansion, that is- penetration is the merely the product of sectional density times velocity.
The reason for this is that as a bullet expands, its sectional density decreases by a significant degree and heavier bullets, having greater initial mass, produce higher sectional density given similar expansion.
For example, if two .45ACP JHPs, one weighing 185 grs @ 1050 fps and the other weighing 230 grs. @ 865 fps were to both expand to 0.68" at impact, the expanded 230 gr JHP would have an initial sectional density of 0.161 and an expanded sectional density of 0.071 whereas the 185 gr. JHP would have an initial sectional density of 0.129 and an expanded sectional density of 0.057.
Doesn't sound like much of a difference 'til you look farther...
Comparing these two examples using the Schwartz bullet penetration model, it is easy to see the benefit of heavy-for-caliber JHPs-
-the .45ACP 185 gr @ 1050 fps that expands to 0.68" would penetrate to a depth of 12.31 inches and permanently crush 2.20 ounces of soft tissue along the way, whereas
-the .45ACP 230 gr @ 865 fps that expands to 0.68" would penetrate to a depth of 13.34 inches and permanently crush 2.40 ounces of soft tissue along the way
So, even though the heavier 230 gr JHP has ~18% less velocity than the 185 gr JHP, it still penetrates deeper and crushes more soft tissue than the lighter, faster 185 gr. JHP.