SpudFiles

Mixing number: 150
Projectile diameter: 12mm
Projectile mass: 7g
Tube length: 100cm
Combustion chamber volume: 20cc
Target: 10mm a3 steel plate.
This is a picture of a 12mm steel ball impacting a 10mm steel plate. The bullet is embedded in the steel plate and cannot be removed. There is a bulge on the back. How much kinetic energy do you think this impact contains? Can it be compared with the 7.62×39mm intermediate rifle bullet? I know that the bullet fired by ak47 can pierce a 10mm steel plate, but the cross-sectional area of the bullet is different, which will affect the penetration. I wonder if the total energy can reach the level of the intermediate rifle bullet?

yyt wrote: ↑

Tue Jan 31, 2023 1:04 am

Mixing number: 150
Projectile diameter: 12mm
Projectile mass: 7g
Tube length: 100cm
Combustion chamber volume: 20cc
Target: 10mm a3 steel plate.
This is a picture of a 12mm steel ball impacting a 10mm steel plate. The bullet is embedded in the steel plate and cannot be removed. There is a bulge on the back. How much kinetic energy do you think this impact contains? Can it be compared with the 7.62×39mm intermediate rifle bullet? I know that the bullet fired by ak47 can pierce a 10mm steel plate, but the cross-sectional area of the bullet is different, which will affect the penetration. I wonder if the total energy can reach the level of the intermediate rifle bullet?

Tough to say, maybe not 7.62 round, closer to something like 556 probably. It's really hard to judge it against modern rounds since steel ball is not as good at penetration as bullet shape due to energy being spread on the higher surface area.

This is just a guess but I would say roughly 1100J of energy at muzzle. Few years ago I experimented quite a bit with high mix hybrids and figured out some formulas that can be used to estimate muzzle energy.

Jimboishere wrote: ↑

Wed Feb 01, 2023 7:10 am

yyt wrote: ↑

Tue Jan 31, 2023 1:04 am

Mixing number: 150
Projectile diameter: 12mm
Projectile mass: 7g
Tube length: 100cm
Combustion chamber volume: 20cc
Target: 10mm a3 steel plate.
This is a picture of a 12mm steel ball impacting a 10mm steel plate. The bullet is embedded in the steel plate and cannot be removed. There is a bulge on the back. How much kinetic energy do you think this impact contains? Can it be compared with the 7.62×39mm intermediate rifle bullet? I know that the bullet fired by ak47 can pierce a 10mm steel plate, but the cross-sectional area of the bullet is different, which will affect the penetration. I wonder if the total energy can reach the level of the intermediate rifle bullet?

Tough to say, maybe not 7.62 round, closer to something like 556 probably. It's really hard to judge it against modern rounds since steel ball is not as good at penetration as bullet shape due to energy being spread on the higher surface area.

Did you see those pictures? They are in another post with the same title. This post failed to add pictures, but I don't know how to delete it.

yyt wrote: ↑

Thu Feb 02, 2023 3:34 am

Jimboishere wrote: ↑

Wed Feb 01, 2023 7:10 am

yyt wrote: ↑

Tue Jan 31, 2023 1:04 am

Mixing number: 150
Projectile diameter: 12mm
Projectile mass: 7g
Tube length: 100cm
Combustion chamber volume: 20cc
Target: 10mm a3 steel plate.
This is a picture of a 12mm steel ball impacting a 10mm steel plate. The bullet is embedded in the steel plate and cannot be removed. There is a bulge on the back. How much kinetic energy do you think this impact contains? Can it be compared with the 7.62×39mm intermediate rifle bullet? I know that the bullet fired by ak47 can pierce a 10mm steel plate, but the cross-sectional area of the bullet is different, which will affect the penetration. I wonder if the total energy can reach the level of the intermediate rifle bullet?

Tough to say, maybe not 7.62 round, closer to something like 556 or stuff like .45 acp ammo(judging by the specs https://gritrsports.com/shooting/ammuni ... -acp-ammo/ ) probably. It's really hard to judge it against modern rounds since steel ball is not as good at penetration as bullet shape due to energy being spread on the higher surface area.

Did you see those pictures? They are in another post with the same title. This post failed to add pictures, but I don't know how to delete it.

Yep, was looking at 2nd screen and accidentally posted in wrong thread It's a good dent on photos, but as I said before, calculating is hard when shape of the projectile differs THIS much.

About the only way you're really going to get an idea of muzzle energy is to run it through a chronograph, or if you don't have access to one, shoot into a ballistic pendulum. The latter is very easy to set up; with a mobile phone as camera ad some calculations you can get some very accurate results. "Penetration of x mm steel sheet" is absolutely arbitrary unless all you're interested in is "can I penetrate steel sheet of x mm thickness?"

picture thread for reference, that is extremely impressive, congratulations!

Can it be compared with the 7.62×39mm intermediate rifle bullet? I know that the bullet fired by ak47 can pierce a 10mm steel plate, but the cross-sectional area of the bullet is different, which will affect the penetration.

Sectional density is indeed an important factor to consider here. It's 0.195 psi for a typical Chinese AK steel core round, compared to 0.069 psi for your 12mm steel ball, that's almost 3 times greater for the AK bullet meaning it would be a much better penetrator, even if they have the same kinetic energy.

It's also worth noting that the steel core is even smaller in diameter and slightly pointed:



Given that you've managed to drive that projectile at least half way through the plate, I think it's safe to say that in terms of energy you're definitely in the same ballpark as an intermediate rifle round

mrfoo wrote: ↑

Thu Feb 02, 2023 12:16 pm

About the only way you're really going to get an idea of muzzle energy is to run it through a chronograph, or if you don't have access to one, shoot into a ballistic pendulum. The latter is very easy to set up; with a mobile phone as camera ad some calculations you can get some very accurate results. "Penetration of x mm steel sheet" is absolutely arbitrary unless all you're interested in is "can I penetrate steel sheet of x mm thickness?"

I have a cheap speedometer, but the strong airflow seems to affect its accuracy, resulting in some very strange data.

jackssmirkingrevenge wrote: ↑

Fri Feb 03, 2023 10:09 am

picture thread for reference, that is extremely impressive, congratulations!

Can it be compared with the 7.62×39mm intermediate rifle bullet? I know that the bullet fired by ak47 can pierce a 10mm steel plate, but the cross-sectional area of the bullet is different, which will affect the penetration.

Sectional density is indeed an important factor to consider here. It's 0.195 psi for a typical Chinese AK steel core round, compared to 0.069 psi for your 12mm steel ball, that's almost 3 times greater for the AK bullet meaning it would be a much better penetrator, even if they have the same kinetic energy.

It's also worth noting that the steel core is even smaller in diameter and slightly pointed:



Given that you've managed to drive that projectile at least half way through the plate, I think it's safe to say that in terms of energy you're definitely in the same ballpark as an intermediate rifle round

exciting

Stabilizing Finn wrote: ↑

Wed Feb 01, 2023 11:03 am

This is just a guess but I would say roughly 1100J of energy at muzzle. Few years ago I experimented quite a bit with high mix hybrids and figured out some formulas that can be used to estimate muzzle energy.

What is the formula? Can they exceed the accuracy of hgdt?

yyt wrote: ↑

Fri Feb 03, 2023 8:05 pm

Stabilizing Finn wrote: ↑

Wed Feb 01, 2023 11:03 am

This is just a guess but I would say roughly 1100J of energy at muzzle. Few years ago I experimented quite a bit with high mix hybrids and figured out some formulas that can be used to estimate muzzle energy.

What is the formula? Can they exceed the accuracy of hgdt?

Formulas that I used are quite specific to that launcher that I experimented with. But simple calculation with available energy and efficiency gets you quite close in my experience.
Using figure 3.75J energy in milliliter of propane times chamber volume times efficiency gets rough muzzle energy.
So 3.75J x 20ml = 75J then 75 x 150 = 11250J of energy in chamber. 11250 x 0.1 = 1125J. (0.1 being efficiency of 10%)

Only real way to determine muzzle energy is knowing mass of projectile and velocity. If you can measure muzzle velocity, then it is easy and very accurate to modify that formula to estimate muzzle energy at specific mix numbers.

I don't know if my energy estimations are anywhere close to real world but in my experiments with those figures I'm able to figure out my launchers muzzle energy very close.

Tried sometime ago to shoot 8mm steel ball bearing to steel plate and got similar resault, ball embedded itself into the plate and did not penetrate (6mm thick plate if remember correctly). Then switched to .223 barrel and shot 55 grain fmj with same mix number and it went straight trough and left clean hole. So projectile shape has huge impact how well it penetrates.