Weight Vs. Speed

[D.Hayden]

Is there a general rule of thumb, about bullet weights.

Now I'm shooting

124 for 9MM - I'm going to try 147's next

180 for 40sw

230 for 45ACP

for the 40 and 45, are these good weights?

If the power factor is equal, how can it matter to bring down steel? It's alway mass * speed right?

[Flexmoney]

Those are all effective weight bullets for the given calibers. No worries.

[ErikW]

There are lots of rules of thumb about bullet weights. Are you interested only in the ability to knock down steel targets?

I always felt the lighter 9mm bullets were iffy taking down Pepper Poppers and 147s did a better job. This is at Minor velocities. However, a 115 from a Major .38 Super does a fantastic job of taking down steel, having 400 fps more velocity than a Minor 9mm 115.

The only problem with the 230 is you'll get a little bit of long-range bullet drop if you are loading to 165-170 PF. The 180's drop is minute. All the 9mm bullets fly flat, even at Minor.

[pcschwenke]

I do a fair bit of steel shooting and I'll give you a bit of info. Bullet weight x velocity gives you power factor but, doesn't always give you best outcome for steel. Here is why, lighter bullets will disapate more energy at the point of impact but, not much momentum. Heavy bullets give you more momentum regardless of velocity.

I use 200gr RN bullets in 38 special for that very reason. They are going ~680fps but, tumble large pepper poppers with ease and reload very quickly.

Any 40 or 45 load is fine and not need to change bullets with them. I shoot 200gr SWC in the 45 ACP at ~ 780 fps.

Biggest thing to remember is that when you shoot, continue on and don't wait for the steel to fall. This is what seperates the best from the rest.

Paul

[D.Hayden]

Thanks for the responses.

I was asking about steel specifiacally, because I've heard that larger bullets work better, I hadn't heard anything about longer ranges, but that makes sense.

If I move from a 124 to a 147, or a 230 to a 200, does recoil change as trhe speed changes?

[Brazos Custom]

If you are just talking about how well a bullet will take down steel then assuming the same power factor the lighter bullet will do better. Kinetic energy is more important than power factor in that calculation. Kinetic energy = 1/2 mass times velocity squared so the velocity component is more important than the mass. 115's at major power factor will take down steel much better than 200 gr bullets.

[TBF]

If you are just talking about how well a bullet will take down steel then assuming the same power factor the lighter bullet will do better. Kinetic energy is more important than power factor in that calculation. Kinetic energy = 1/2 mass times velocity squared so the velocity component is more important than the mass. 115's at major power factor will take down steel much better than 200 gr bullets.

If this is true, then, pins are the opposite.

For pins I have noticed a distinct advantage with heavier bullets.

I don't shoot much steel, but Iv'e not noticed any staying up with 200 grainers in 45acp.

Travis F.

[Brazos Custom]

For pins you have another variable, you have to dump the kinetic energy into the pin not just blow through it. Larger caliber bullets with more cross section put more energy in the pin. Also if the bullet is going too fast it will just go right through the pin and carry some of the energy with it. Heavier, larger caliber bullets make more sense for pins.

[EricW]

If you are just talking about how well a bullet will take down steel then assuming the same power factor the lighter bullet will do better.  Kinetic energy is more important than power factor in that calculation. Kinetic energy = 1/2 mass times velocity squared so the velocity component is more important than the mass. 115's at major power factor will take down steel much better than 200 gr bullets.

If this is true, then, pins are the opposite.

For pins I have noticed a distinct advantage with heavier bullets.

I don't shoot much steel, but Iv'e not noticed any staying up with 200 grainers in 45acp.

Travis F.

The reason heavy bullets work better on pins is because momentum, not kinetic energy is the dominant factor in taking down the pin. If the bullet didn't "stick" into the pin (ideally), it would be a different story.

[D.Hayden]

If you are just talking about how well a bullet will take down steel then assuming the same power factor the lighter bullet will do better. Kinetic energy is more important than power factor in that calculation. Kinetic energy = 1/2 mass times velocity squared so the velocity component is more important than the mass. 115's at major power factor will take down steel much better than 200 gr bullets.

SO in general are you saying lighter is better all around, or is there some tradeoff?

For 45 do you think 185's or 200's would be better than 230's (assuming they all shoot paper equally well)?

[Phil Dunlop]

BarKim, the tradeoff is that the gun feels snappier to shoot with the lighter bullets, and can be harder to control.

In the case of the 40 most shooters seem to have settled on bullets around 180 gn. Some prefering the softer push of 200gns and some the sharp and snappy feel of 155gn

Its a matter of personal preference at major p/f though if you were shooting the mover in NRA you might concider a bullet traveling at +1000f/s to keep your aim on paper.

P.D.

[MoNsTeR]

Heavy bullets give you more momentum regardless of velocity.

Not so. Momentum formula:

p = mv

Of course, we also call mass * velocity "power factor". So if heavy bullets at the same PF are better at taking down steel or pins, the reason isn't momentum.

[tightloop]

We have gone back in time to the late '70's. That was always the knock on 9mm that you had to hit steel high to take it down. Subsequently, shooters developed the "don't send a boy to do a mans job" attitude. slower heavier bullets, always seemed to take steel down more efficiently, but ultimately, it is the shooter placing the bullet in the right spot. You can get away with lower hits with major PF, no doubt.

All in all, you pay your money and take your chances. Hit 'em correctly, they fall to minor PF.

[ErikW]

Hit 'em correctly, they fall to minor PF.

Unless they are out of adjustment or broken. Then you spend an extra .5 - 2.0 second making it up, or you let it go and gamble on calibration. And there's a good chance your little bullet knocked it back into adjustment so you'll end up with a Miss.

Life ain't fair and neither is IPSC/USPSA steel.