[peng]

Yes, and yes. It's simply comparative, not real world. It really is only defined at an impact velocity. Most LE trained "firearms experts" opposite of me use muzzle velocity. If my client is so inclined, pretty easy to get them excluded under Daubert for common and simple mistakes.

Thanks, makes sense.

There is actually a program i use. SD changes as the bullet expands, weight/dia sq, the expanding bullet dia is getting larger, weight is the same. Why its really a metric for solids, not expanding bullets, but its still relative. Drive identical weight bullets the same vel, the larger expanding bullet penetrates less.

Got it. Are my calculations right though? We came up with 2 very different numbers for SD.

I assumed this was a 10mm round.

 

[dla]

Thanks, makes sense.



Got it. Are my calculations right though? We came up with 2 very different numbers for SD.

I assumed this was a 10mm round.

Your SD calculations agree with mine.
.138 for the 155 and .160 for the 180.

 

[fredj338]

Thanks, makes sense.



Got it. Are my calculations right though? We came up with 2 very different numbers for SD.

I assumed this was a 10mm round.

Yes, looking at the program, i put in inches instead of mm. Must be euro zone.
155/.143
180/166

 

[fredj338]

https://en.wikipedia.org/wiki/Impact_depth

Muscle is 1.04grams/cm2
lead is 11.34grams/cm2
180gr is .631"
155gr is .580"
The 180gr bullet is 9% longer than the 155gr.
Since according to Newton, penetration is directly proportional to object length, the 180gr bullet will always penetrate 9% further than the 155gr.

No not always, look at the gel shots i posted. Vel & momentum are a big part of penetration.

 

[Railsplitter]

Since according to Newton, penetration is directly proportional to object length, the 180gr bullet will always penetrate 9% further than the 155gr.

This is true if the velocity of the two are equal. A difference in velocity between the two weights and Newtons observation goes out the window. Then there is variations in bullet expansion which further complicates things. In other words heavy doesn't mean the best penetration.

 

[dla]

This is true if the velocity of the true are equal. A difference in velocity between the two weights and Newtons observation goes out the window. Then there is variations in bullet expansion which further complicates things. In other words heavy doesn't mean the best penetration.

No, they both have exactly the same momentum. Since the weights are different, the velocities must be different as well.

Newton's observation is just a shorthand method of predicting penetration and doesn't address the complexities of deforming/expanding bullets.

Bullet density matters a lot. If you switch from lead (11.34gm/cc) to tungsten (18.xxgm/cc) the penetration will increase proportionally. If you increase the weight (assuming lead), the length of the bullet increases, and Newton says the penetration increases proportionally.

 

[Diabloman]

Imagine we have two hardcast bullets of the same profile, same diameter, differing only in weight and length. They are both launched so that they have identical momentum(e.g 155gr @1350fps and 180gr @1162fps). Which will penetrate further and why?

Bullet weight....weight penetrates. i.e. a 230 gr 45acp bullet will penetrate a pine 4x4 @ 900 fps. Bullet weight!? fwiw

 

[fredj338]

Bullet weight....weight penetrates. i.e. a 230 gr 45acp bullet will penetrate a pine 4x4 @ 900 fps. Bullet weight!? fwiw

Only in solids. Once you start expanding bullets, penetration is directly related to frontal area, the changing SecDen. Plenty of 230/45 jhp that wont penetrate as much as some 124/9mm jhp.

 

[Railsplitter]

No, they both have exactly the same momentum. Since the weights are different, the velocities must be different as well.

Newton's observation is just a shorthand method of predicting penetration and doesn't address the complexities of deforming/expanding bullets.

Bullet density matters a lot. If you switch from lead (11.34gm/cc) to tungsten (18.xxgm/cc) the penetration will increase proportionally. If you increase the weight (assuming lead), the length of the bullet increases, and Newton says the penetration increases proportionally.

Yes like I said when the velocities change energy and momentum change as the velocity changes.

 

[CPotts]

Would someone please take the 'theoretical' out to the real world and shoot up some jello and tell us what you results you got.

 

[fredj338]

Would someone please take the 'theoretical' out to the real world and shoot up some jello and tell us what you results you got.

Already been done. Luckygunner labs isnt perfect but it is a valid comparison of diff calibers & bullets.

 

[Supersquatch]

Would someone please take the 'theoretical' out to the real world and shoot up some jello and tell us what you results you got.

If I'm making Jello I'm eating it.