So some of the posts have been really helpful for rifles

Photon Guy my best advice for you is to seek a cartridge in 6.5mm to .308 calibers, and spend some time looking over ballistic tables. If its main purpose is hunting then look at bullets with a BC of .400 plus for your research. When leaving the muzzle at speeds of 2700 to 3100 fps you'll find that with a BC of .400+ it'll give you decent trajectories and plenty of energy to handle most North American big game.
 
Well to bring in some further discussion on physics, momentum which is represented by P is a product of the mass and velocity. Now I would think the main factor in a bullet slowing down prior to exiting the muzzle is air resistance. If you were to shoot a gun in the vacuum of space the bullet would maintain its velocity indefinitely. In the earth's atmosphere however the air resistance will slow it down. How quickly the bullet is slowed down I would think would depend on its momentum. Now it doesn't matter if you've got a more massive slower moving bullet or a less massive faster bullet mass and velocity both have an equal effect on the momentum. So if the momentum is the same I don't see how a more massive but slower bullet would maintain its velocity better than if it were vice versa.
 
Photon Guy, why do I think that this discussion has no actual purpose other than your personal amusement? If you really wanted a new rifle, more than enough info has been shared with you (by extremely knowledgable folks) to make your choice well informed.

Go buy a rifle and tell us what and why.
 
Photon Guy said:
Well to bring in some further discussion on physics, momentum which is represented by P is a product of the mass and velocity. Now I would think the main factor in a bullet slowing down prior to exiting the muzzle is air resistance. If you were to shoot a gun in the vacuum of space the bullet would maintain its velocity indefinitely. In the earth's atmosphere however the air resistance will slow it down. How quickly the bullet is slowed down I would think would depend on its momentum. Now it doesn't matter if you've got a more massive slower moving bullet or a less massive faster bullet mass and velocity both have an equal effect on the momentum. So if the momentum is the same I don't see how a more massive but slower bullet would maintain its velocity better than if it were vice versa.
Click to expand...

Well physics is part of ballistics, but you're also ignoring aerodynamics in all your figures. Ballistics Coefficient or BC is the bullets ability to overcome the forces acting upon it after leaving the barrel. A bullet does not slow down prior to exiting the muzzle, not unless your barrel is so long that all the powder is consumed a long before the bullet exits.

Bullets with a higher BC resist the effects of drag better, to get a more streamlined bullet you need to increase the length and as a result the weight. You also need enough bearing surface on a bullet to engage the rifling to spin the bullet enough to stabilize its flight and to have enough surface to get proper tension when seating in the cartridge case. So in lighter bullets you can't make as streamlined of a bullet to resist drag as you can with heavier bullets and have enough bearing surface to work properly.

The only way to get a light bullet with a high BC is to drop bore diameter. So if you want to shoot a 90 grain bullet like you posted in your other thread your better off going to a 6mm bore rifle than a .277 caliber. So while you're not wrong in your physics, you're not correct in your ballistics.

I recommend you read this article by Bryan Litz. Here is a little quote from it:
Bryan Litz said:
It’s a generally accepted fact that the heaviest bullet in a given caliber is the best bullet to use for long range target shooting. There are several credible studies of this topic, [Ref2] [Ref3] and it is one of the fundamental truths of long range ballistic performance. Assuming constant form factors (drag profiles), heavy bullets will have higher BC’s than lighter bullets of the same caliber. Heavier bullets will also have lower muzzle velocities than lighter bullets, but when loaded to the same pressure, the higher BC of the heavier bullet is more valuable than the higher muzzle velocity in terms of retained velocity and wind deflection at long range. German Salazar put it aptly: “Muzzle velocity is a depreciating asset, not unlike a new car, but BC, like diamonds, is forever.” For this reason, the present discussion focuses on the heaviest bullets available in each caliber.
Click to expand...
 
Since the 270 Winchester has been mentioned here; it's a fairly well known, "fact", that the lighter 130 grain load with its higher velocity shoots with a bit flatter trajectory than the heavier 150 grain load. A lesser I own fact, is that when 150 grain bullets are used, they actually shoot with a flatter trajectory than the 130 grain bullets when the range is substantially longer, and they arrive on target with substantially more energy. Of course, this assumes that both bullets are otherwise identical in their points and bases. High muzzle velocity is worth something, but it's also overrated. When it comes to long range, ballistic coefficient is more important.
 
Photon Guy, why do I think that this discussion has no actual purpose other than your personal amusement?
Click to expand...
I don't know. There is no way I would know what you're thinking or why you're thinking it.

If you really wanted a new rifle, more than enough info has been shared with you (by extremely knowledgable folks) to make your choice well informed.

Go buy a rifle and tell us what and why.
Click to expand...
I will, when I can afford it. Right now Im saving up and Im looking to buy a Cooper or a Dakota Arms.
 
Well physics is part of ballistics, but you're also ignoring aerodynamics in all your figures. Ballistics Coefficient or BC is the bullets ability to overcome the forces acting upon it after leaving the barrel. A bullet does not slow down prior to exiting the muzzle, not unless your barrel is so long that all the powder is consumed a long before the bullet exits.

Bullets with a higher BC resist the effects of drag better, to get a more streamlined bullet you need to increase the length and as a result the weight. You also need enough bearing surface on a bullet to engage the rifling to spin the bullet enough to stabilize its flight and to have enough surface to get proper tension when seating in the cartridge case. So in lighter bullets you can't make as streamlined of a bullet to resist drag as you can with heavier bullets and have enough bearing surface to work properly.

The only way to get a light bullet with a high BC is to drop bore diameter. So if you want to shoot a 90 grain bullet like you posted in your other thread your better off going to a 6mm bore rifle than a .277 caliber. So while you're not wrong in your physics, you're not correct in your ballistics.
Click to expand...

I used the wrong words in my previous post, a mistake on my part. When I said the bullet slows down prior to leaving the muzzle what I meant to say is that the bullet starts to slow down after it leaves the muzzle and no longer has the pressure behind it. But as you said, a bullet will only slow down prior to leaving the muzzle if the powder is all burned up well before it leaves the muzzle. Usually the bullet will be at maximum velocity just as it exits the muzzle. As the bullet is traveling down the muzzle it will be accelerating the whole time and then without the pressure and with the air resistance it will start to lose speed as it leaves the barrel.

Anyway, you seem to have a background in physics yourself, are you an engineer by any chance? As for me I took physics in high school and in college and while I by no means consider myself a bonifide expert I do know a few things. And I do find physics fascinating.
 
Probably better to learn the trajectory for whatever cartridge is chosen, for shots beyond, say, 300 yards. Inside of 300, "It don't make no nevermind, nohow." On out past 300, most folks can't guesstimate plus or minus fifty yards. The laser rangefinder is a blessing. :)

I've always zeroed for 200 yards. At 300, a 130-grain .270 drops about five inches. A 150-grain '06 drops about six inches. Bambi will never notice.
 
Physics is both fascinating and confusing. So many ( laws ) in physics and lots of formulas. I understand you like velocity. As a kid I shot alot of things with my pellet guns. .177 and .22 cal Benjamin's that were both very accurate and capable of killing all the small game around the house. If you pumped the rifle 5 times you could see the pellets in flight and they knocked cans down. Pump it 10 times and you couldn't see the pellet unless the sun was just right and the cans often went flying. These were the old metal cans back in the day not flimsy coke cans of today. Got a Lil older and started shooting 22's and other small rifles. Armadillos were the best target for me because the hard shell aided in expanding the bullets on impact. Man I can remember like it was yesterday the first time I shot one with a 220 swift.

I have since learned that bullet construction can help the slower cartridges can preform much like the high velocity cartridges if you chose the right ones. I shoot very soft bullets thru slower rounds and a tougher bullet thru high velocity chamberings.

The physics between the velocity and the density of the bullet transferring all its energy into soft tissue and fluid filled cavities is the fascinating part. That's why shooting a watermelon with a ballistic tip is much more explosive than shooting it with a fmj.
 
Physics is both fascinating and confusing. So many ( laws ) in physics and lots of formulas.
Click to expand...

You just got to break it down and take it step by step. There are lots of laws and formulas but after using them so often they can become second nature. I never did more of the advanced Physics which uses Calculus but even basic physics can be challenging, and its fun once you get into it.
 
It is all a compromise.

Gravity is a constant, so "Flat Shooting" is all about velocity. In reality, it is not that important at normal hunting ranges. Zero your rifle at 200, and hold high a bit at 300, or you can adjust your scope. How much you hold off with one cartridge vs another is really irrelevant, provided you know the number for the rifle you are shooting (~7.5" for the .30-06, ~6" for the 270). Where "Flat Shooting" is a benefit is when you get the range call wrong, but in reality, at reasonable hunting ranges, it is not enough to matter.

If you think Bambi is at 300 yards, and he is actually at 325, a 150gr .30-06 will be ~3 inches low. A "flat shooting" 130gr .270, in the same situation will be ~2.5 inches low.

At longer ranges, you call the range 500 yards and it is really 525, the .270 will be 5.6" low, the .30-06 will be 7.7" low. Assuming a perfect hold and shot, both would probably still hit, but neither would be a good hit, most likely. Most people have no business shooting that far anyway.

Keep in mind too, that drag is based on the square of the velocity, so higher velocity bullets shed speed quicker the faster you drive them. For example, even a bullet with a pretty good BC, for example the Hornady 6.5mm 140gr Extremely Low Drag Match (0.610 G1 BC), if you somehow were able to launch it at 4000 fps, it would lose ~175fps in the first hundred yards. At a more realistic but still fast 3000fps it loses ~160fps in the first 100 yards, and a pretty slow 2000fps it drops ~128fps.

If the bullet sucks ballisticly, for example the .17cal 20gr Hornady VMAX (0.185 G1 BC), from a .17 Remington at 4000fps loses 638 FPS in the first 100 yards.

You also haven't mentioned sectional density, witch for a given caliber increases with bullet weight.

In other words, for most North American hunting, as long as the cartridge is of adequate power, and you use an appropriate bullet, any of them will work fine, and if you do your part, Bambi won't know that he was hit with a 90 gr .243, 140gr 6.5 Creedmoor, 130 gr .270, 180 gr .30-06, or a 200gr 8mm Mauser, or anything in between.

So in other words, here are most of the things you need to balance when deciding on a cartridge.

Sectional density
Velocity
Energy
Ballistic Coefficient
Barrel life
Recoil
Cartridge OAL (short/long action)
Ammo/component availability

If I was shopping for a general purpose, sporter weight hunting rifle, I would probably look for a 6.5 Creedmoor. The .264" 140gr is a sweet spot for all of the above except ammo availability (you probably aren't going to find it on the shelf at WalMart), but reloading components are readily available. With the 140 gr hunting bullets (Sierra GameKing, Hornady Interlock, etc) it is fine for anything in the lower 48 short of big bears, and I wouldn't hunt those anyway. There are also light (<100gr) varmint bullets available.
 
Since we know the bullet starts dropping as soon as it leaves the barrel, we pick a point where we want the rifle zeroed.

If we are shooting closer or farther, we will either be low or high.

So somebody, a long time ago made little knobs for our sights so we can adjust, and be dead on for what ever range we want to shoot.

In reading these post, I see people say a bullet from a X cal. will drop a certain amount at a given range where a Y cal bullet will drop +/- more or less then bullet Y.

Maybe so, in a vacuum. I don't shoot in a vacuum but I do know its more then cal. that makes a bullet drop more or less then another bullet.

There is such a thing called ballistic inequality. Meaning some bullets pass through the air better then others.

I just picked up my Lyman Reloading guide and turned to 30 cal bullets. Just off hand I picked 200 gr bullets. One has a BC of .481, another has a BC of .565. Everything else being equal the higher BC bullets will have less drop then the lower BC bullets.

Why? Because we cant shoot in a vacuum, we have air the bullet needs to pass through, which tends to slow down the bullet via drag.

We know if you drop two objects straight down, they will hit the ground at the same time. If barrel is level, it will hit the ground at the same time as one dropped straight down if dropped from the same height.

The difference is the bullet will drop a ways from the barrel. The higher the BC the farther from the barrel it will drop.

Its been said, that the best sniper is the one with the best gun, fastest bullet, and best scope.

I don't agree with that, I contend that the best sniper is the one who learns to weaponized math.

In other words, learning you rifle, your ammo and what the environment
does to the bullet from that rifle in flight.

You can compensate for a slower bullet, by making a few more clicks on your sights. You can choose a bullet that is designed to work at the distance of your target.
 
In reading these post, I see people say a bullet from a X cal. will drop a certain amount at a given range where a Y cal bullet will drop +/- more or less then bullet Y.

Maybe so, in a vacuum. I don't shoot in a vacuum but I do know its more then cal. that makes a bullet drop more or less then another bullet.
Click to expand...

I think the only person saying comparing anything is me, and the numbers I posted were at sea level, 29.92 in Hg.

If you have two rifles, both with a 1.5" scope height and a 200 yard zero, one in .270 shooting a 130 grain Spitzer Boattail GameKing at 3200FPS, and the other a .30-06 shooting a 150 grain Spitzer Boattail GameKing at 2900 FPS, the .270 trajectory will absolutely be "flatter".

The .30-06 will have a higher apogee before the zero range (about .4 of an inch at 125 yards), and drop off faster after the zero range, about 2" lower at 300. This is entirely due to velocity and flight time. The .30-06 takes longer to reach the target, and is effected by gravity longer, so it drops more.

In this case, the .270 has a higher muzzle velocity and a higher BC.

My point is that in the grand scheme of things for a hunting rifle, the difference between a "flat shooting" .270 and a non-flat shooting .30-06 is not really enough to care about when choosing a medium game cartridge.

As long as you know your rifle and where it shoots at a given range, "flat shooting" just doesn't matter.
 
Gravity is a constant. The acceleration due to gravity on Earth is 9.8 m/s squared and that's how it is with all objects regardless if the object is heavy or light. If the Earth didn't have an atmosphere you could drop a small rock and a large rock at the same time and they would both hit the ground at the same time. The rate of fall would be the same for both rocks 9.8 m/s squared. Supposedly they did that experiment on the moon which is in a vacuum. The difference here on Earth is that Earth does have an atmosphere and that will slow the rate of fall since the rocks would have to push the air aside as they're falling towards the ground.
When you plug in the equation F=MA (Force = Mass times Acceleration) the larger more massive rock will fall with more force than the smaller rock and thus it will push the air aside faster and fall faster. Now, as with bullets if you apply that same principle a bigger bullet will fall faster. A bullet of more grains will fall faster and thus its trajectory will be more of an arc. Also it will not go as far since it will hit the ground sooner. So a lighter faster bullet will not only have a more flat trajectory it will also go further. Now, I never got far enough in Physics to understand about how drag affects velocity and how its the velocity squared that's lost when it comes to drag but that would be another fascinating topic of discussion and something else to take in as a factor.
 
When you plug in the equation F=MA (Force = Mass times Acceleration) the larger more massive rock will fall with more force than the smaller rock and thus it will push the air aside faster and fall faster.
Click to expand...
No, this is incorrect. Acceleration is constant (gravity), so the larger rock will hit the ground with more force than the smaller rock, but they will hit at the same time. Go in your back yard and try it.

Now, as with bullets if you apply that same principle a bigger bullet will fall faster.
Click to expand...
Again, incorrect. The acceleration of gravity is constant.

A bullet of more grains will fall faster and thus its trajectory will be more of an arc.
Click to expand...
No, the trajectory is more of an arc because, generally speaking, the heavier the bullet the lower the velocity. There is more of an arc, because the lower velocity allows more time for gravity to act on the bullet.

Also it will not go as far since it will hit the ground sooner.
Click to expand...

Assuming the barrel is level, and the rifles are at the same height above the ground, the heavier and lighter bullets will hit the ground at the same time. The lighter bullet will go farther, because at a higher velocity it will cover more distance in that time, but the time for the bullet to drop from the muzzle level to the ground will be the same, the same as if the bullet was simply dropped from that height rather than fired.

Mythbusters confirmed this with a .45 ACP one episode: https://www.youtube.com/watch?v=D9wQVIEdKh8

So a lighter faster bullet will not only have a more flat trajectory it will also go further.
Click to expand...
Depending on you are comparing it to, but even if true, this is meaningless. Any rifle bullet will travel way farther than you can see, let alone shoot accurately. Who cares that one bullet will travel 4600 yards and another will only go 4200? It is the equivalent of "I fired an arrow into the air, it fell to earth I know not where".

Now, I never got far enough in Physics to understand about how drag affects velocity and how its the velocity squared that's lost when it comes to drag but that would be another fascinating topic of discussion and something else to take in as a factor.
Click to expand...

Run some numbers.

http://www.jbmballistics.com
 
No, this is incorrect. Acceleration is constant (gravity), so the larger rock will hit the ground with more force than the smaller rock, but they will hit at the same time. Go in your back yard and try it.
Click to expand...
Acceleration from gravity is constant but you also have to take into account air resistance. Both the small rock and the big rock have to push the air out of the way as they fall. The larger rock being more massive will push against the air harder than the small rock. We're talking about an environment that has an atmosphere, not a vacuum.
 
We're sure chasing this one down a rabbit hole! The physics discussion is being taken to a whole new level. The OP needs to forget physics and start studying the science of projectiles in flight called "ballistics". Physics alone can't answer his questions.

I love the "weaponizing math" kraigwy! I might have to steal that one in the future. My best advice is keep it simple, pick a caliber that has a large selection of projectiles with a decent BC. Make sure the rifle you choose has an adequate twist rate to stabilize the bullets you want to use. Find a cartridge with enough capacity to push your bullets 2700-3100 FPS at the muzzle and I can guarantee everything else will fall in place.
 
I don't think the air will have any measurable effect on rocks being dropped for the first few seconds of falling. Dropped from 30,000 feet, I'm sure it would get to a velocity that the air resistance would have a large effect and the rock would probably reach a stable velocity if it's round, perhaps even slow down as the air gets denser. But a bullet fired level over a level plain from the altitude of the shooter's shoulder standing-off-hand will hit the ground at the same instant as a pebble dropped at the same exact time and altitude above the ground. I could be technically wrong, but that would be quibbling over nothing. The air resists the bullet's forward travel because its velocity is thousands of feet per second. But the air will not resist the bullet's vertical fall from your shoulder to the ground. Sometimes I think the quest to be technically correct can lead us to be practically wrong.
 
Acceleration from gravity is constant but you also have to take into account air resistance. Both the small rock and the big rock have to push the air out of the way as they fall.
Click to expand...

The air resistance at the vertical velocities we are talking about is less than trivial. Remember, drag is to the square of the velocity, and with the comparatively slow acceleration rate of gravity, and the generally short flight times (1/3 to 1/2 second at normal hunting ranges), velocity on the vertical axis never gets high enough to have any real effect.

In .1/2 seconds of freefall an object will be traveling ~4.9 m/sec or ~16.1 fps.

Again, this can be tested with a big rock and a little rock in your back yard.

Bullets in flight work the same way. The horizontal velocity of the bullet has no effect on the acceleration of gravity toward the ground. See the Mythbusters video above.

Now if there was a minute or so of freefall, I suppose what you describe could happen, as the objects near terminal velocity, but that simply does not happen with rifle bullets.

The larger rock being more massive will push against the air harder than the small rock. We're talking about an environment that has an atmosphere, not a vacuum.
Click to expand...
Well, it would in theory have more frontal area and more air resistance, so if this was the case, it would actually fall slower and the smaller object would hit first, but it would require more time in freefall to reach a vertical velocity where drag would be an issue, which is why you need to factor in drag and frontal area when calculating terminal velocity. Also why a skydiver falls slower in a belly-down fall than headfirst. More frontal area = lower speed, even though the mass is unchanged.

Again, at the vertical velocities of a rifle bullet in flight, this is trivial at worst.

Not sure if it is any consolation, but Aristotle agreed with you around 330 BC, but Galileo proved him wrong around 1600 AD.

You are making this way more complicated than it actually is.
 
What I'm looking for is a good high quality hunting rifle for medium to large game. I was considering the Steyr but after some research I might instead settle for a Cooper or a Dakota Arms. I've got a Remington 750 in .30-06 but Im looking for something more high end and preferably bolt action. And a round of similar size to the .30-06 but with more velocity.
Click to expand...

And the irony here is that a $200.00 Lee-Enfield might do just as well as your $1200-1500 wonders; "Good" is such a subjective term...:)
 
You must log in or register to reply here.
Back
Top