light vs. heavy bullets on poppers

[dv8]

Moderator's Note: This topic is thread drift spun-off from a post about shooting Minor in Limited and L-10.[/url]

Even if you hit all A's on paper, the steel is another story. Those poppers are not always calibrated all that well to go down on minor PF. Besides, PF is not always a guarantee - heavy bullets at slower velocities simply don't work. But even when those poppers do go down, the do it so much slower that it takes up to a couple of seconds - that is an eternity, and sometimes you just can't help but shoot that popper again, losing time and rounds... And I don't even want to talk about the wind - too much to laugh about for those shooting major...

Edited April 29, 2004 by Erik Warren

[tightloop]

dv8

I have NEVER seen or shot a popper or steel of any kind that a 230 gr bullet at 165Pf would not take over, same with 200 gr, same with 185 gr.

Jake

I like your attitude...

[Jake Di Vita]

Thanks buddy.

[dv8]

I have NEVER seen or shot a popper or steel of any kind that a 230 gr bullet at 165Pf would not take over, same with 200 gr, same with 185 gr.

I was talking about minor. A particularly popular load 147 gr bullet over 3.2 gr N310. This load flies a bullet at 906 fps out of my CZ Combat 85 (133 PF), and I have a video where PMS factory loads (115 gr, don't know velocity, but I wouldn't be surprised if it didn't make 125 PF) very slowly but still successfully knock some steel down, and then my wonderfull 133 PF loads keep dinging on those poppers doing nothing but silly music. With the same PF, lighter bullet takes less energy to rebound from target, hence transfering more energy to the target... well. I think... Since I was the shooter on that video taken just last Sunday - I need no more proof to what I said earlier. I am picking up my G35 coming Friday, and there will be no more aming at the very top of steel targets for me. I am shooting Production with 40 SW from now on, and if Jake is right (I think he is) - my scores are going up soon.

By the way, do those Scherer mag tubes work?

[dv8]

When I was shooting factory ammo I had very few steel problems - probably due to calibration variations, or possibly just hitting it not high enough. But all factory ammo I ever used was 115 gr. It is when I shoot 147gr at 900 fps that I have a lot more frequent problems with steel. (am I the only one?) Again, this is just a guess, but it seems to me that higher velocity with lighter bullet will be more effective than heavy bullet at lower velocities - that is within the same PF of course.

Did anybody else have similar experience, or am I missing something here?

[Flexmoney]

I like to think that heavier bullets take steel down a bit better (given the same power factor). I think they are more likely to push on the steel a bit more...transferring their energy better. Whereas light bullets hit steel with a quicker snap. With a perfectly square hit...it doesn' likely matter much. As the angle of the hit increase then the lighter bullet might be more likely to "skip" some of it's energy off the steel.

Just my own thoughts...I haven't tested that at all.

[dv8]

That's exactly what I thought first too. But on the second thought, there's gotta be some difference in how the energy is transferred from the bullet to a perfectly motionless target vs. not fixed target, such as a popper or a plate. Plus, there is the bullet bouncing back off the steel - does heavy bullet take more energy away from impact to rebounce?

I am not that good at mechanics, so the only way for me to check this out would be to load different kinds of ammo and set up some steel and chronograph... some day, perhaps...

[pangris]

While far from being an expert in this, pure, theoretical physics says you should be able to knock it over better with faster, lighter bullets. In practice... ? I personally carry a .45 with a 3.6" barrel, so I favor heavy slow bullets in real life. If I listened to theory, I'd carry a 357 SIG.

Seems like, if you were going to shoot slow enough to make sure every hit count, you could count out your rounds and put some hot ones in for the steel. I bet a 147 gr at 1150 would take it down pretty well I'm sure there are a bunch of good reasons not to do that, but if everything went right...

Paul

[dv8]

While far from being an expert in this, pure, theoretical physics says you should be able to knock it over better with faster, lighter bullets. In practice... ?

Practice shouldn't go far from theory, unless wrong theory is applied...

Here is another little question: Given the same PF 10 foot away from a muzzle, wouldn't a heavier bullet loose velocity faster than a lighter one down the road?

That's probably what it is.

Eh?

[dv8]

Seems like, if you were going to shoot slow enough to make sure every hit count, you could count out your rounds and put some hot ones in for the steel. I bet a 147 gr at 1150 would take it down pretty well I'm sure there are a bunch of good reasons not to do that, but if everything went right...

Paul

Paul,

That's the area where practice doesn't go along with the theory! At least at my level. May be more advanced shooters can do that, but I can screw up even a classifier plan, not even talking about a field course

As for sending 147 gr at 1150 fps using N310 - you are absolutely right, there are TONS of reasons not to do it! Staying alive would be one of them.

Be safe!

Vlad

[rhino]

Putting down steel isn't about energy transfer, it's about momentum transfer (impulse). The reason why heavier bullets will do better is because they retain more momentum longer after impact because more of the momentum is due to mass and is therefore less dependent on velocity.

At the same power factor (which is actually a measurement of momentum), obviously a lighter, faster bullet will have more available kinetic energy because velocity is the key. With momentum, velocity and mass are equal contributors.

[pangris]

Seems like, if you were going to shoot slow enough to make sure every hit count, you could count out your rounds and put some hot ones in for the steel. I bet a 147 gr at 1150 would take it down pretty well    I'm sure there are a bunch of good reasons not to do that, but if everything went right...

Paul

Paul,

That's the area where practice doesn't go along with the theory! At least at my level. May be more advanced shooters can do that, but I can screw up even a classifier plan, not even talking about a field course

As for sending 147 gr at 1150 fps using N310 - you are absolutely right, there are TONS of reasons not to do it! Staying alive would be one of them.

Be safe!

Vlad

147 at 1150? No biggie. Just wear kevlar gloves. And really good eye protection.

I'm new to reloading, too. 1050 be better?

[dv8]

Rhino,

Another question: Let's say a 147 gr bullet is charged with 3.2 gr powder, and another bullet 115 gr is charged with 3.7 gr powder. (This way their PF should be close) If I am not mistaken, the N310 is fast enough to completely burn out before the bullet leaves the 4.5 inch barrel. Which bullet will fly further? I think 115 gr bullet will fly further because lesser mass is propelled with more powder.

If 10 feet from the muzzle their momentum is the same, will it still be the same a 100 feet further? I'd say no, because heavier bullet will lose more energy to travel the last 90 feet, than the lighter bullet.

You are absolutely right that at every given moment the mass and velocity are equal contributors to the momentum for both bullets. The question is how the energy is spent while in flight, and how momentum is split between the bullet and the popper at the time of the impact.

What I am not sure of is the rate at which heavier and lighter bullets are loosing their energy. I suspect that heavier bullets might still be more effective on very close ranges... don't ask me how close - I have no clue

[dv8]

147 at 1150? No biggie. Just wear kevlar gloves. And really good eye protection.

I'm new to reloading, too. 1050 be better?

Paul,

This is an extremely important question, and it belongs to the reloading forum. I just have to warn you not to play with fast powders untill you have a very good understanding of the pressure in the barrel. Before you familiarize yourself with the reloading safety issues, I must strongly suggest that you don't load any ammo that is not listed in the powder manufacturer's published data. Not that I am such an expert in this myself (which I am not), but because it can be very dangerous. I personally know people that got injured that way.

N310 powder is not listed by manufacturer as suitable for a bullet heavier than 90 gr.

I had a lot of help from a member of this forum when I started reloading, I'd recommend that you get a good advise from experienced reloaders before trying anything new.

Be safe, man.

[mcoliver]

dv8, if you can get past the funny characters IN THIS THREAD maybe it'll shed some light into your questions. good luck.

[pangris]

147 at 1150? No biggie. Just wear kevlar gloves. And really good eye protection.   

I'm new to reloading, too. 1050 be better?

Paul,

This is an extremely important question...

Be safe, man.

I appreciate the sentiment, but I was kidding around. While I'm sure those loads are possible, I am Mr. Safety. The only loads I plan on working up will be factory duplicates +/- a few FPS, and I mean a few. I'm very aware that every time you r gun works PROPERLY there is a controlled explosion of 15-50K PSI about two inches from my fingers - which means when it works improperly... you get the idea... I'm cautious.

I apprieciate the thought, though.

[rhino]

Another question: Let's say a 147 gr bullet is charged with 3.2 gr powder, and another bullet 115 gr is charged with 3.7 gr powder. (This way their PF should be close) If I am not mistaken, the N310 is fast enough to completely burn out before the bullet leaves the 4.5 inch barrel. Which bullet will fly further? I think 115 gr bullet will fly further because lesser mass is propelled with more powder.

Uh, well ... I would expect the 115gr bullet to have a significantly higher muzzle velocity, so it would go farther before it eventually fell to the ground when fired parallel to the ground. I'm not sure if that answers your question or not!

If 10 feet from the muzzle their momentum is the same, will it still be the same a 100 feet further? I'd say no, because heavier bullet will lose more energy to travel the last 90 feet, than the lighter bullet.

They're both decellerating due to resistance by the air as soon as they leave the barrel, so if they coincidentally have the same momentum at some point, it's certainly not going to be the same late.

Momentum = P = mass x velocity = mv ... m is essential fixed in both cases.

I simplify my life by not worrying about energy when it comes to pistol bullets as it yields very little useful information, whether you're talking about external ballistics or terminal ballistics.

[dv8]

dv8, if you can get past the funny characters IN THIS THREAD maybe it'll shed some light into your questions. good luck.

mcoliver,

Thanks man, looks like the guys at the physics forum really dig this stuff.

The answer to our question still appears to be "Velocity". As for major loads, their energy is sufficient to "kick" a popper far enough for it to fall regardless of reasonable velocity variations.

[gm iprod]

Given the same projectile diameter and shape, heavier bullets will be longer and will loose less velocity (a higher Balistic Coefficient) . But at any given pf they will be going much slower and have less velocity to loose. They may, at short range (less then 100Y), have a more loopy trajectory??

From the Sierra Manual. Assuming 143pf

.357gr 110gr JHP. MV=1300fps, energy = 413ft lbs

.357gr JHP. MV=900fps, energy =284ft lbs (32% less energy)

110gr, Zero at 25Y, -.68" at 50Y, -3.02" at 75Y, -7.21" at 100Y. Lost 268fps. Time of flight aprox .257 of a sec. PF at 100 = 113.

158gr, Zero at 25Y, -2.01" at 50Y, -6.96" at 75, -15.00" at 100. Lost 81fps. Time of flight aprox .349 of a sec. PF at 100 = 129.

This proves ??????

If the plate stays up, you probably did not shoot it in the right place.

If you hold the pistol 66" (6ft man with pistol at just below eye level) off the ground and perfectly horizontal the 110gr would hit the ground at about 200yards, the 158gr will land at 170yards. But at the same time, regardless of velocity. Fired with the same ft lbs muzzle energy the heavier will travel further as the difference in velocity would be reduced. Fired at the same speed the heavier bullet will go further again before hitting the ground.

PF evens out the variables of weight versus velocity, to give different advantages to both, but not one over the other, especially where plates are concerned. If we used Muzzle Energy to determine the levels of power then the 158gr proj will be going about 1100fps and will hit the ground somewhere near 225yards, and have 25% more energy left at 100Y.

[Skywalker]

Guys,

let's clear the energy/momentum/velocity issue once and forever.

Physics: initial conditions of the system bullet+popper.

Bullet:

Vb0 = Bullet velocity (supposed constant for all bullet trajectory).

mb0 = Bullet mass

Popper:

Vp0 = Popper velocity before impact = 0

Mp = Popper mass

A = leverage arm from bullet impact point to popper hinge.

Now we need to make some assumptions, to easen the calculations: these assumptions won't have major impact on the conlusions of the survey.

1. The impact between the bullet and the popper is completely elastic. Thus, the fraction of kinetic energy of the bullet, transformed at impact in deformation work of the bullet and of the popper is negligible.

2. The bullet will retain all its mass after impact. Thus, mb1 = mb0 = mb. This is true for a jacketed bullet, while for a lead bullet there will be a small fraction of the bullet lead that will be vapourized at impact, but this fraction is negligible when compared to the whole bullet mass.

3. The bullet velocity after impact is negligible. Thus we will assume Vb1 = 0.

4. There will be no friction of any kind. Thus, the system bullet+popper will preserve its total momentum M = constant => M0 = M1.

Now let's write some simple equations deriving from 4.

System total momentum before impact: M0 = Vp0 * Mp + Vb0 * mb = Vb0 * mb

System total momentum after impact: M1= VPi * Mp + Vb1 * mb1 = VPi * Mp

M1 = M0 => Vb0 * mb = Vp1 * Mp => Vp1 = (Vb0 * mb) / Mp

Now the angular velocity of the popper, the one that gives you the impression a popper falls faster or slower, is w = Vp1 / A, thus:

w = (Vb0 * mb) / (Mp * A)

Let's throw in some ballistic data:

1. a 230grs. bullet travelling @ 850 fps.

2. a 123 grs bullet travelling @ 1200 fps

For the first bullet we will have an angular velocity w = (230 * 850) / (Mp * A) = 195'500

For the second bullet we will have an angular velocity w = (123 * 1200) / (Mp * A) = 147'600

The angular velocity of the first bullet is 32% greater than the second, even if the second bullet was travelling 41% faster.

We can conclude that, for a comparable range of velocities, a heavier bullet will knock down a popper faster than a lighter bullet.

BTW, Power Factor is practically a measure of Momentum, and this demonstrates good ole Col. Cooper knew what he was doing...

[rhino]

We can conclude that, for a comparable range of velocities, a heavier bullet will knock down a popper faster than a lighter bullet.

BTW, Power Factor is practically a measure of Momentum, and this demonstrates good ole Col. Cooper knew what he was doing...

[EricW]

Does it really matter?

I shoot 115gr's out of a short barrel and I have NEVER squarely hit steel that didn't go down. Based on that, I'd say engineering loads to take down steel is a solution in search of a problem.

BTW, the simple physics you guys are using doesn't really describe the problem anyway, since the collision between the bullet and the steel is neither perfectly elastic nor perfectly inelastic. You're really transferring an impulse from the bullet to the steel - which is where it gets very empirical because a lot of it has to do with whether the bullet bounced back, splatters, or just deforms temporarily rides with the plate on its way down.

And no, I'm not going to break out my old mechanics book and start spewing equations. My (and your) time is better spent dryfiring.

[Detlef]

ouch, good that I didn't read any of this thread earlier, shudder! sky, nice calculation (although it really doesn't take getting into angular velocity to capture the physics...), and I agree with it, however, you have only managed to drown the essence of the process in formulae:

m*v is momentum.

Before impact, all momentum is in the bullet, after impact most of it is in the popper. (But not all, I have seen pretty intact bullets (say 230 gr) come back with what must have been 50 ft/sec, so about 5% of the momentum is still in the bullet.)

What you have shown is that the bullet with the higher momentum (which just happens to be the heavier one!!!) knocks down the popper faster. DUH!!!

The point that we are really interested in is:

For a given (!) identical momentum/PF, will a heavier bullet knock down the popper better than a lighter one? So...will a 230 gr .45 at 760 ft/sec (PF 175) knock down the steel better than a 125 gr .38 at 1400 ft/sec (also PF 175)???

The answer is yes, but only for edge hits, because it's bigger! For center hits, the answer is no.

Btw. a popper weighing 150000 gr (about 20 lb) will go down with about 1 ft/sec linear velocity (heck, now I understand why it seems to take forever, IT DOES!) when hit by a 175 PF bullet. That is a kinetic energy of 150000 gr*ft^2/sec^2 (goofy units, but who cares). The incoming bullet had kinetic energy of 245000000 gr*ft^2/sec^2, so almost the entire energy of the incoming bullet was spent on deforming the bullet, the popper, and on heating the two up! This shows that any calculation assuming that the popper will have the same kinetic energy as the incoming bullet is horribly (!) wrong, and that these calculations have to be done using momentum, not energy conservation!

--Detlef

[rhino]

Okay, that's enough of that science and math stuff!

Everyone get back to your reloading rooms ... there's nothing more to see here.

[Detlef]

true, but if I had a dime for every time someone told me he used lighter (or heavier) bullets "because they knock down steel better", I could buy a new gun now....