Penetration/Sectional Density/Velocity ??.

[youngda9]

I have a question about bullet penetration.

I was thinking of loading up a 300 grain load in my .44 magnum rifle (24" barrel) in order to get more penetration on tougher animals like wild hogs. I currently shoot the 240grain XTP at 1825fps, my deer load.

Shooting a lighter bullet, I obviously can get more velocity and energy. How can I tell what the threshold of penetration would be in velocity where a 240gr XTP and 300gr XTP bullet would be the same. Given that these bullets are the same construction and diameter I would think there is a way to calculate this (impact)velocity.

For example, I shoot the 240gr XTP at 1825fps. In order to get the same penetration with the 300gr bullet I have to shoot it to greater than XXXXfps. How do I calculate the velocity that will give the same penetration for a different weight bullet? (or is it much more complicated than that since they will expand at different rates since the impact velocity is different)

Is it just the ratio of the SD (.185*1825fps/.232=1455fps)?

XTP Numbers:
200gr XTP @2150fps, 2053ft-lbs
Sectional Density: 0.155
240gr XTP @1825fps, 1775ft-lbs
Sectional Density: 0.185
300gr XTP @1500fps, 1499ft-lbs
Sectional Density: 0.232

 

[RhinoDefense]

Penetration forecasting isn't a simple formula. There are many things to factor and an "all else equal" doesn't apply. You'll have to do grunt work.

 

[rcmodel]

Yep.

There is no way to tell without trying it.

Any expanding bullet is limited in penetration by how much it expands at the velocity you are shooting it.

When the bullet expands, it's just exactly like opening the drag chute on a funny-car.
The bigger the chute, the quicker it slows down & stops.

I would expect the 300 XTP to give deeper penetration, because it won't expand as fast or as much as the lighter 240 bullet at attainable .44 Mag velocity.

How much more can only be determined by testing.

rc

 

[CraigC]

IMHO, the XTP is a little too lightly constructed for its weight and has a reputation for separating at the moment of truth. I prefer cast bullets but if you want a good jacketed bullet for larger wild hogs, look no further than the 270gr Gold Dot. It's a toughly constructed bullet with a bonded core and stands up to .444 pressures and velocities.

 

[jaybirdjtski]

If you want penetration and "killing ability" go with a hardcast lead with a wide meplat.
Cast Performance makes a 300 grn with a .31" meplat.
Beartooth makes a WFNGC 300 grn with a .340" meplat. (wide flat nose gas check)
You should get 3' of penetration at least. These penetrate in a straight line and will shoot through a big pig front to back or the other way around or through both shoulders.
The wide meplats typically have a wound channel 2x the diameter due to the flat nose.
Think of standing in front of a Mack truck.
Performance is predictable, reliable and deadly. In a handgun these bullets would be bear loads. A pig would be kid's play. For the ultimate in penetration....like you want to kill a Cape Buffalo with your 44, Belt Mtn Punch 300 grn at $2.50 each. Not uncommon for these to break both shoulders on a bison or penetrate 4' through a big animal.
Forget all the calculations. Big bullets at moderate speeds with flat noses penetrate and kill. I know all about ft/lbs and that but the performance of hardcast with wide flat noses has to be experienced. The white hunters in 19th century Africa already had it figured out. So did the buffalo hunters in America.
I have a 454 Casull SRH and like Beartooth bullets. Uniform, accurate and they flat out work on animals! Of course, you give up downrange performance as they do not have pointy noses or boat tail design but up to 150 yards, you will kill anything you hit in the right area.

added: I have load data showing up to 1650 fps / 1800 ft/lbs with a 300 grn bullet and a 24" bbl. You won't need it however!

 

[Captcurt]

I shoot the 300gr XTP in my ruger inline and it works fine, but I am only cranking about 1200 fps in it. CraigC is probably right about the xtp being a little too thinskinned when you crank it up to 1800 fps.

BTW Craig, I'll have to try the Gold Dot.