Years ago I got into the habit of testing my reloads a number of different ways.

I took them to the range on hot days to do informal "pressure" tests while testing their accuracy potential and their speed.

Next I would do sone more informal penetration tests using soaked bundles of newspapers or soaked phonebooks tied together.

Finally, I would test my bullets on game.

Almost without exception my own informal testing showed that given the same make of bullet, and same impact velocity - the higher the sectional density - the deeper the penetration. It seemed to matter much more than caliber, bullet weight or energy, when predicting penetration.

"Famous penetrators" that either i or my buddies tested included 160 grain 6.5's, 175 grain 7mm's, 220 grain 30 caliber's and 250 grain 338's. In almost every case I remember, a smaller caliber, when combined with a signifigantly higher sectional density bullet - would out-penetrate larger calibers shooting bullets with poorer sectional density. These old experiments, and my subsequent testing on game - made me a fan of long bullets.

I know that my own testing was very limited in scope and complexity. I never had the chance to use any really big-bores growing up, as I knew no one who used anything bigger than a .375.I'd like to ask the collective wisdom of my fellow forum mates to share the results of any of their own back-yard penetration tests, and any conclusions they've formed as a result of their own experiments.

Thanks,

Penetration depends on momentum Weight x Velocity. With equal bullet weights the smaller caliber will penetrate furthur, and have the higher sectional density. As you pointed out with a given diameter a longer bullet weighs more.
Good luck!

The only real number to predict penetration is MV/(pi)r^2 where r = the radius of the bullet, or half its diameter.

This is (Momentum of the bullet)/(cross-sectional area of the bullet).

Sectional density is a crude shorthand figure of merit which is based on a square bullet that is a bullet caliber on each side of the square cross-sectional fictitious bullet.


There is an optimum balance point of bullet momentum (for comfort in shooting and carry-weight of the cannon that shoots that momentum down range, and back at you), balanced against size of bore of that sporting cannon.

Smaller bore with more momentum wins, as long as the bullet is stout enough to handle it.

Legal-minimum-wise and practically in the field, the .375 caliber wins all contests.