*New Results* Forward Velocity vs Bullet RPM....which “hits” harder?

[AckleymanII]

Thawed turkey's or Ham would work better, 12 lb minimum.

 

[AllThingsAI]

The gentleman that performed this test saw similar non-expanding results from 55g Vmax (TAP) bullets through drywall. Hmmm....40g VMax fragmented so I will try those and use drywall backed with thin leather to catch the drywall debris.

Bullet Drywall test
https://how-i-did-it.org/drywall/results.html

 

[PigButtons]

Couldn't you hang a 6" long 3" dia. piece of salami or something similar in front of a 2' x 2' backer board of some sort and measure the spray pattern? It may not allow for measuring the dissolution of the bullet, but it should make the splatter factor obvious.

 

[NC308]

Wouldn’t an slow motion video while shot thru clear ballistic gel show the same thing? It should show the fragmentation pattern along with the energy transfer? Not sure how to measure it but it would definitely be visible.

 

[AllThingsAI]

Wouldn’t an slow motion video while shot thru clear ballistic gel show the same thing? It should show the fragmentation pattern along with the energy transfer? Not sure how to measure it but it would definitely be visible.

Not sure...I really want a simple repeatable way to measure. Paper makes nice prints, all I need is just to get the bullet to expand. I’m going to try drywall and maybe a thin piece of aluminum. One thing I do know is I don’t want anything impeding the fragments once it starts.

How amazing would it be to have high speed video! Just look at the price of the cameras fast enough to capture a rifle bullet....BIG $$$

 

[Knotwild]

I'm certainly the least educated person in this ballistic room, but I am really interested in the results. It seems that bullet needs something substantial enough to compromise the bullets integrity. Paper and rabbit fur - seems like a bullet could sail right through it because there is very little resistance to make the jacket start to fail or drive the plastic tip back into the bullet to start the expansion. In other words, it may be that it's going to take some resistance in the beginning to start things out. Maybe a two or three layers of leather, stretched over a frame wet, tacked, and let it dry so it's tight.

 

[AllThingsAI]

Test 2 Preliminary Update

Bullet 40g VMax
Expansion Media - 1/8" Thick Aluminum plate
Detection paper starting @ 1" from back of aluminum plate
- 8 pieces of paper spaced every 1/2"

I did a get bullet expansion!
I'm reviewing all the material now and will work to process the information into an easy to view format for the forum....but I do see a result. I will say that since I used card stock spaced out in even increments I'm able to trace individual pieces of bullet over the majority of the distance (I should be able to calculate the rate of expansion based on this interesting observation, I don't think you could ever do this with gel or meat). I will post without a conclusion and let the you all come to your own conclusions.

Stay tuned....it's going to get interesting!

 

[AllThingsAI]

Test 2 results

40g Vmax
Velocity ~ 3300fps
1:12 and 1:8 Twist Barrels:

Here are the images of layers 1, 5, and 8. Each layer is 1/2" apart. So distance from layer 1 to 5 is 2". Distance from 5 to 8 is 1.5" Layer 1 was 1" from 1/8" thick aluminum plate. There are two pics. First is the front of layers 1,5,8, the second is the back layers 1,5,8. The distance markers on each card is 1" for measurement reference. I'll post individual pictures later.

 

[CharlieNC]

Wet newspaper has been used a lot to simulate viscous tissue.

 

[David Milisock]

Test 1 Summary: No expansion from either .224 55g VMax bullet. Bullets were both fired at ~ 3040fps from 1:12 and 1:8 twist 223’s. Clean holes all the way through both sets of test paper. I need to revisit the first layer of the target to get expansion initiated....clearly the 55g Vmax is tougher than anticipated.

Current first layer used rabbit fur, backed with 1/16” of modeling clay, then attached to card stock.....this yielded zero expansion.

Any thoughts on a better first layer expansion media? I’m going to scrap the fur, it’s a PITA and gets everywhere. I can just use bare leather instead.

I’m glad it was only 110 degrees outside today! I think I’ll wait for it to cool off a bit before I retest.

The test will be hard to do. Even the 40 grain VMAX has been shot from a 22 250 at 4350 FPS with a 1 in 9 twist that's about 5,800 RPS.

 

[rebel]

Like @Knotwild, I don't claim to be any sort of ballstician. I think you are missing a key component in your ballistic media that some have suggested - hydraulic pressure. What makes a critter blow up? It's water content. Water doesn't come close to simulating a real critter, it is non compressible, however it is repeatable and easy to clean up I would use a small Styrofoam cup or zip lock bag of water in front of your target to initiate expansion.

 

[AllThingsAI]

Like @Knotwild, I don't claim to be any sort of ballstician. I think you are missing a key component in your ballistic media that some have suggested - hydraulic pressure. What makes a critter blow up? It's water content. Water doesn't come close to simulating a real critter, it is non compressible, however it is repeatable and easy to clean up I would use a small Styrofoam cup or zip lock bag of water in front of your target to initiate expansion.

Purposely trying to avoid the hydraulic shock factor. I’m trying to measure the fragmentation difference (if any) due to spin. I was able to do this...see the results of test 2

This is a cause and effect issue....in my mind it’s the bullet that causes the Hydraulic shock effect on tissue. Once you understand what is happening with the bullet itself the you can better understand/model the hydraulic effect. Now we are getting into hydrodynamics...yikes! Big question for me is how does the sonic shockwave play into this hydraulic effect? Shoot one bullet slightly below the speed of sound and another slightly above it (both into gel)...that would be interesting and something I haven’t seen.

 

[yotehater]

Any thought to the size of the hollow point? The old Speer "Flying Ashtrays" were always spectacular on prairie dogs.

 

[AllThingsAI]

Started a new thread for results to keep things clean

Results thread:
http://forum.accurateshooter.com/threads/test-results-forward-velocity-vs-bullet-rpm.4012308/

 

[AllThingsAI]

Any thought to the size of the hollow point? The old Speer "Flying Ashtrays" were always spectacular on prairie dogs.

Bullet construction is complicated business. Lots of factors come into play...but I have a theory that shorter stubbier bullets will concentrate energy over a smaller Surface area and come apart easier...just a theory.

 

[rebel]

Seen it

Purposely trying to avoid the hydraulic shock factor. I’m trying to measure the fragmentation difference (if any) due to spin. I was able to do this...see the results of test 2

This is a cause and effect issue....in my mind it’s the bullet that causes the Hydraulic shock effect on tissue. Once you understand what is happening with the bullet itself the you can better understand/model the hydraulic effect. Now we are getting into hydrodynamics...yikes! Big question for me is how does the sonic shockwave play into this hydraulic effect? Shoot one bullet slightly below the speed of sound and another slightly above it (both into gel)...that would be interesting and something I haven’t seen.

Seen it a bunch, 300 BLK does both really well. I have tested a lot of purpose built subsonic bullets for hunting. At 1000 fps, you need Hydrodynamics. Try a 190 SMK through ballistic media with a road kill deer behind it - you won't recover the bullet.
Not disagreeing just posting experiences. I understand what you are doing, interested in the results, but I'm not sure it proves a splat factor. If you shoot a bullet designed for minimum expansion at 1800 fps subsonic, it pencils through just like that SMK described. Not gonna goof up your other thread with my theories AI. Glad someone else enjoys testing stuff.

 

[AllThingsAI]

Seen it

Seen it a bunch, 300 BLK does both really well. I have tested a lot of purpose built subsonic bullets for hunting. At 1000 fps, you need Hydrodynamics. Try a 190 SMK through ballistic media with a road kill deer behind it - you won't recover the bullet.
Not disagreeing just posting experiences. I understand what you are doing, interested in the results, but I'm not sure it proves a splat factor. If you shoot a bullet designed for minimum expansion at 1800 fps subsonic, it pencils through just like that SMK described. Not gonna goof up your other thread with my theories AI. Glad someone else enjoys testing stuff.

Understanding what is going on is a lot of fun! And I agree with you on proving splat factor (very subjective)...just trying to make sense of what is happening. But if a bullet does expand in a more efficient way because of spin it should cause more hydraulic (but thats another order of magnitude more complicated...step 1 first! (at least that's where my small brain takes me). Thanks for the reply...I enjoy learning what others have experienced.

 

[Ackman]

On PD's in Arizona, I did a side by side comparison with 2-223's. Both custom barrels. A bolt gun with 14 twist shooting 50gr Blitz (not the BK) @ 3450. And an AR15 with 10tw shooting Sierra 55BTHP slower at maybe 3150 (?, I'm guessing). They both demolished PD's, but at a few hundred fps slower velocity the 55 splat factor was just a little better.....the extra weight or the twist? I'd still choose the 14tw, that barrel was just stupid easy to dial in and shot most anything I put through it. The 10tw was much fussier about loads and took longer to get dialed.

 

[BobbyJ]

When the material properties are factored in the complexity goes up exponentially. Distributed forces along a rotating bullet of a given construction is where the material scientists come in and I lose my steam. I’m getting too old for differential equations!

I did calculate the total energy for both forward motion and rotation using a 55g 6mm bullet

Forward: 1490J @ 914.4m/s (3000fps)
2648J @ 1219m/s (4000fps)

Rotational: 4.19J @ 150,000RPM
16.75J @ 300,000RPM

So you are 100% correct that the forward kinetic energy dominates the rotational....but the rotational energy will send fragments out radially with 4x the force (when RPM doubles) once impact occurs. So the Fragment dispersion cone should be greater and dump more of that forward kinetic energy over a larger area.

Had to dust off the calculator! Feel free to check my math, the conversions can always bite you.

From what I have read in real world testing is the high rpms seem to give more POP and wow on Pdogs. People using a 1/12 twist say that a 1/8 or 1/9 at the same velocites give more POP. The only major difference is the RPMS.
While its true most of the energy is forward motion when the bullet hits something those calculations miss some of the picture of whats actually going on. The bullets is spinning then gets squashed into a larger diameater in a fraction of a second. Those rpms might cause it to pancake to a larger diameter which would tend to fragment which might be why they seem to be more explosive than what the math shows.

10j rotational vs 2500j of forward does not seem like it would matter much but if testing shows otherwise it means the math is missing something. It could be it just causes a larger pancake = faster deceleration = more explosiveness, the faster rotation might just serve to expand it more and faster.

 

[357Mag]

Understanding what is going on is a lot of fun! And I agree with you on proving splat factor (very subjective)...just trying to make sense of what is happening. But if a bullet does expand in a more efficient way because of spin it should cause more hydraulic (but thats another order of magnitude more complicated...step 1 first! (at least that's where my small brain takes me). Thanks for the reply...I enjoy learni

t others have experienced.

Allthings -

Howdy !

OK.... thinking out loud.

Varmint shooting ( PDs for example ):

- The bullet chosen / fired into the target ( or target animal ) does not itself carry any fluids in it.

- When shooting ( example ) varmints, " Red Mist " ... " Splat " and similar descritptions are referencing the forceful ejection of fluids, tissue, bone fragments and such from within the animals carcas to outside of the
carcas. This involves the transfer of energy from the bullet to / into the animal.

- When energy transfer reaches sufficient levels, the animals carcas cannot contain all of the energy.
Energy levels can be reached that cannot physically be contained inside the animal's carcas.

- IF a theoretical aerodynamically-stabilized bullet could be delivered at distance that would obturate and
come to rest completely inside of the carcas, the maximum amount of bullet energy would be transfered to the animal w/o any consideration being required for spin of the bullet. By extension, then......

- IF a spin-stabilized bullet can be delivered at distance, that would obturate and come to rest
completely inside the carcas; the maximum amount of bullet energy would be transfered to the animal
w/o any consideration being required for spin of the bullet. In other words.... if a theoretical spin- stabilized bullet that would in-essence pancake out flat while inside the carcas.....maximum energy transfer would take place as the bullet decelerated rapidly inside the carcase. All the enrgy would be dumped into the animal. Bullet spin would not add energy available for " transfer ". Spin would alter some of the mechanics of the ways / means of energy transfer.

- Organic components that originate within the animal that are forcefully ejected to then become
external to the carcas carry away with them some of the delivered energy. Therefore, external cues that
the carcas has been ruptured are evidence that excess energy has been delivered to the animal.....
amounts of energy the carcase can not contain. " Red Mist " then, actually conotes the fact that a certain amount of the delivered energy has become ejecta, and therefore.... not all of the energy was
contained within the carcas. In other words, not a complete energy " dump " inside the animal .

- The above seems to indicate energy transfer based highly upon fluid dynamics. Bullet fragments
or shrapnel would not be propelling much / most of the external ejecta. The displacement of the animal's body fluids, tissue, and so forth becomes so violent from the ( excess ) energy transfer that they carry away with them energy to the outside environement.

- In the real world, the spin-stabilized varmint bullet fragments due to violent expansion, and that expansion
is affected by not only the bullet's forward velocity, but also things like bullet design, construction; and materials ( to name a few ).

- For purposes of the test, use of say Hornady's .224" cal 55gr bullets would offer multple different bullets of the same calibre & wt. You could compare their 55gr SP , 55 SX SP, 55gr w/ cannelure; etc.
* I mention the 55SX because Hornady's SX bullet has a comparatively thin .009" jacket.
Or more to the point, compare the 55SX to the 55V-Max and say... Sierra's 55 Blitz King ?

My point:
There's a whole bunch of energy transfer taking place that is not dependent of bullet rpm, in the classic sense. The rpm is first & foremost needed to keep the bullet stabilized out to the desired engagement distace, with a useful amount of accuracy. PD's can be blown up by enough fwd velocity on a ( " varmint " ) bullet. Certainly, in instances where the " temporary wound cavity " driven in-part by the bullet's shock wave
is of a size that exceeds the width / depth of the animal.

What I am suggesting is a kill mechanism that is a function of excessive energy being applied, to the point where the carcase cannot contain it. HOW much excess, is up to the shooter.


With regards,
357Mag




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