Poppers And Power Factors

[ajax]

This is for a non USPSA match , my question is will there be a difference between 100 grain and 124 grain 9mm bullets ability to take down poppers if the power factors are the same or will the heavier bullet have a better chance of taking them down?

I'm hitting the Knob Creek pistol match this coming weekend and they set their poppers really light but want to make sure if I use the 100 grainers they will still take them down.

Thanks

Ajax

[AzShooter]

The heavier bullet will take the poppers over more reliably even at the same power factor. What you are looking at is Kenetic Energy to knock the poppers over and a slow moving heavy object will prove to be more adapt at this.

[AlamoShooter]

IF... the hinges were perfect and the steel had no slop in the movment = I do not think you would see a difference. And I use a 95 grain bullet in my Revolver for our steel matches and we use knock down targets too. It allways works fine.

But the steel hinges are not allways in good shape and AZShooter is right. = use the heavier bullet

[Schutzenmeister]

Ajax

I think it's mainly in the calibration of the Poppers. I've seen them set light enough that the average 22 LR would take them down, and heavy enough that a 45 with milspec ball barely moves them. In general though, I have to agree that bigger and slower is more reliable.

Consider this extreem example on a bowling pin: A slow moving bowling ball will almost certainly knock a bowling pin over while a faster moving bullet with the same PF could easily shoot right through the pin and still leave it standing. So if you want to knock something over, I'd tend to agree big and slow is probably better than small and fast.

Just my 2 cents ...

[Gun Geek]

The heavier bullet will take the poppers over more reliably even at the same power factor. What you are looking at is Kenetic Energy to knock the poppers over and a slow moving heavy object will prove to be more adapt at this.

Sorry, got this backwards. At a given powerfactor, the lighter bullet would have more KE than the heavier bullet. KE is 1/2 x m x v^2 (squared). KE is more sensitive to changes in velocity than in mass.

My quick calculations (on the back of my electric bill) show that the lighter bullet (at a 125pf) will have about 25% more KE than the heavier bullet at the same pf.

The other part of the story is momentum, which is m x v. But we already know it is the same since the powerfactor is the same (yeah I know, weight and mass are not the same, but it works for this discussion).

It is my observation as well that the heavier bullets tend to do a better job knocking things over. But why?

It has to do with the time the bullet spends pushing the target (longer with a slower bullet) and, with the amount of energy used to deform (destroy the bullet). A small fast bullet (i.e. 9mm) is completely destroyed when hitting steel (ever find anything other than an occasional jacket?. Big slow ones are not destroyed - you can regualrly find 45's especially FMJ after they hit steel.

Now I'm getting interested. I wonder what speed I would have to throw a baseball to get a pf of 125,000. Wonder if it would do a better job on a popper than a 9mm? Hmm...

[Schutzenmeister]

Now I'm getting interested. I wonder what speed I would have to throw a baseball to get a pf of 125,000. Wonder if it would do a better job on a popper than a 9mm? Hmm...

Let's see ... My 1-ton diesel 4x4 ... Hmmmm. Curb weight about 7850 lbs. Hmmm ... That's about 54,950,000 grains. Now for the math to make a 125 PF ... Hmmmm ... That's about 0.00227(...) feet per second. (Or about 0.027 inches per second ...)

You're on the right track Gun Geek ... My theory is that Poppers are more "pushed" down than "knocked" down. By contrast, assume a 1 grain bullet at 125000 fps ... I suspect one of two things would occur. Either the bullet would pass straight through the popper, or simply disintergrate on impact. Either way, I don't believe it would "knock" anything down, and it simply does not have the duration of impact to "push" anything over.

I have a son that's a physics major ... I wonder if I could interest him in building a rail gun to test our theories?

[herky]

Maybe Flexmoney will chime in with his "Dwell time on Steel with JHP's" theory.

[Gun Geek]

OK 45 second on the Google calculator and I got the following:

A baseball is no more than 150grams, which is about 2315grains.

For a 125000 pf, I would need to throw it about 54fps (125000/2315 = 54)

54 fps is about 37 mph. I can do this! (I was clocked in Highshcool at about 60mph)

Next time I get to the range, I'm taking a baseball. I wonder what the president of the pistol club will say if he sees me throwing a baseball at a popper or plate rack! Probably laugh because I'll have to throw a dozen times before I hit the darn thing.

My gut tells me the baseball will take the plate over faster than my 9mm loads at 130pf.

Now we're having fun!

Ask that physics major what he thinks...

[Schutzenmeister]

Now there's an idea for a start position ... Standing naturally on pitcher's mound, baseball in hand. Gun is in locked box in front of pitcher. On start signal, using only the baseball and while remaining on the pitcher's mound, knock over the Popper at home plate. Knocking over the Popper unlocks the case holding the gun. Retrieve gun and engage the RO ... err, I mean running target (sorry!) before he can safely make it to first base.

Remember, three strikes and YOU'RE out!

(I got WAY too much time on my hands tonight!!!)

[XRe]

Inertia is, I believe, the physics principle you guys are searching for. It's harder to change the momentum of an object with more mass. Ignoring, for the moment, the energy expended upon breaking a bullet up and how that might affect all the fun things like retained and transferred energy, etc... if both bullets were to stay intact, the heavier bullet would have more resistance to acceleration (deceleration is really acceleration in the opposite direction). The .45 slug is going to be harder to slow down.....

Carry it through from there... I can't explain it in all the fun physics gobbledeygook language, but...

[G7.]

Momentum = mass times velocity. (AKA Power Factor)

Kinetic Energy = 1/2 mass times (velocity squared).

"Conserved" means momentum before the collision equals momentum after the collision. (or KE before = KE after)

Momentum is conserved in ALL collisions. Kinetic Energy is only conserved in perfectly elastic collisions (billiard balls, knock-knocks, ball bearings). Bullets hitting poppers is an example that is much closer to an INELASTIC collision (two lumps of clay colliding - and then sticking together).

The best-case scenario for us as shooters would be if the bullet could impact the steel, and then stay stuck to it. Of course, this won't happen, but second best is where there is the bullet does NOT splatter, and just falls - in a thud - to the ground.

If the bullet splatters, the momentum, which is conserved - is partially lost in the sum of all the little masses, times velocities, going sideways.

In an equal-momentum situation (and = PF) say a 100 gr bullet going 1250 fps vs a 125 gr bullet going 1000 fps, (both PF = 125) the heavier bullet has the edge ONLY because it probably will not break up as easily. If both could stick to the steel, both would knock it over equally fast/as well.

This is why .45 works so well on steel -- and pins. Not only is the momentum good, the bullets stay together because the velocity is lower.

[Cuz]

You guys are making my head spin. Did I log into the wrong forum this evening???

-Cuz.

[kruger]

The best-case scenario for us as shooters would be if the bullet could impact the steel, and then stay stuck to it. Of course, this won't happen, but second best is where there is the bullet does NOT splatter, and just falls - in a thud - to the ground.

Errr... wouldn't the best case be when the bullet bounces back? Both the incoming momentum and the outgoing momentum of the bullet would be transfered to the steel. The next best case would be if the bullet just stops all forward movement. The worst case would be if the bullet retains some forward momentum (like if it stuck to the steel).

If the bullet splatters, the momentum, which is conserved - is partially lost in the sum of all the little masses, times velocities, going sideways.

Momentum is a vector quantity. A change in motion in an direction orthogonal to the original momentum vector does not change the magnitude of the vector in the original direction. However, any fragments whose velocity vector has a component in the orignal direction would have a effect based on that component vector.

My apologies for any errors, it's been a while since I've done basic kinematics.

Ahhh, the memories.

Wistfully,

Mark Kruger

[Flexmoney]

Maybe Flexmoney will chime in with his "Dwell time on Steel with JHP's" theory.

Hey...I read that in a reloading book.

The idea being that some bullet shapes can dwell (hang onto...stick) on the steel better than others...thus, transferring more of their energy to the steel.

I always liked to think of that like throwing rocks in the water. The shape and size of the rock can be a factor in how it dissipates energy. A big gnarly rock is going to sink right into the water. Where other sizes and shapes can be skipped over the surface of the water. Those (skipping) rocks, once they enter the water, can even flutter through the water on their way to the bottom...which spreads out the energy even more.

Now, I really don't know that JHP's transfer any more energy to the poppers or if they don't.

[G7.]

Errr... wouldn't the best case be when the bullet bounces back? Both the incoming momentum and the outgoing momentum of the bullet would be transfered to the steel.

No, because then the momentum of the bullet bouncing back would be wasted in NOT pushing the popper over. (Same for the splatter going sideways, it too is wasted as far as being used as "WORK" in the physics sense, to push the steel over)

Velocity and Monemtum both are vector quantities, and we want all those vectors pushing the plate over, not going sideways as splatter; or backward. Any bouncing is wasted, (and hazardous to the shooter )

[herky]

Flex, it's your theory and you can spin it anyway you want to.

[Flexmoney]

I usually do.

I like to throw that out there when I get amazed looks when (mostly newer) shooters see me using JHP's. They look at me like I am crazy. I assume that is because they equate JHP's as being expensive...like those boxes of "defense" rounds that are sold in 20 round boxes. (Could be they think I am crazy for other reasons too.)

[hopalong]

I DO !!!!!! (think your crazy for other reasons)

Showing you some

HOP

[shred]

Errr... wouldn't the best case be when the bullet bounces back? Both the incoming momentum and the outgoing momentum of the bullet would be transfered to the steel.

No, because then the momentum of the bullet bouncing back would be wasted in NOT pushing the popper over. (Same for the splatter going sideways, it too is wasted as far as being used as "WORK" in the physics sense, to push the steel over)

Velocity and Monemtum both are vector quantities, and we want all those vectors pushing the plate over, not going sideways as splatter; or backward. Any bouncing is wasted, (and hazardous to the shooter )

Elastic vs inelastic collisions. Indeed a bounce is the best at knocking things over.

[ewokUk]

So would a 110 grain bullet with a PF of 115 (at the target) drop a ful-sized popper?

I'm thinking of using a hot .30M1 & this is what the ballistic calculator come out with at 300m.

Mind you I'll have to use 40" of Kentucky windage!

[LPatterson]

So would a 110 grain bullet with a PF of 115 (at the target) drop a ful-sized popper?

I'm thinking of using a hot .30M1 & this is what the ballistic calculator come out with at 300m.

Mind you I'll have to use 40" of Kentucky windage!

That's going to be 1 fast M1 if you hope to get 1045 FPS @ 300 yards. I think you should run that through a ballistic calculator to find a starting velocity.

[Schutzenmeister]

M1 Carbine? Assuming you actually HIT the Popper at 300 , You might have a chance. Why not compare the PF of your Carbine to that of what is left of a .223 at 300? A 55g bullet won't have all that much left on it at 300, I wouldn't think ...

[Harmon]

M1 carbine sierra bullet starting out at 1900 fps(per the sierra manual) will be exactly 1045 fps at 300 yards.

Is that going to be fast for a m1 carbine? not hardly. it should knock the steel over at 300 too.