270 and Long Distance

[helotaxi]

ahh, but the 280AI gets just about to 7mm mag with out all the recoil, or so I am told.

No free lunch. With the velocity comes the recoil. No way around it. That said, the 7mm Mag isn't a very hard kicker anyway. Not something I'd want to settle down behind for a long day at the bench but 20-40 rounds with a good recoil pad, even with a really light rifle aren't uncomfortable.

On the -06 format, don't forget the 6.5-06. For a given BC and SD, 6.5 bullets are going to be lighter than their 7mm counterpart meaning that velocity stays about the same, despite the reduction in bullet base area, and recoil is reduced. I'm in the 280 AI camp personally simply because I already keep 7mm bullets on hand (though my next project is my long range hunting rifle in 7 WSM) but if you're not already committed to a certain caliber, it's worth a thought.

[FUBAR]

Someone said long range shooting is speed, well many with speed just fall off...

No revaluation, but it's-- speed + weight + BC. ( I would add sectional density for long range hunting)

However, tell that to the guys shooting 45-70s and such out to 1200 yards, with iron sights! Plus they have been doing it for 100 years or so!

A 270 will serve you well, study the published load data, and work yourself up a load. That's what's fun to me, getting the most out of each rifle...

Just for the record, I have a very fine 7mm mag, and a very fine 280AI. I consider my 280AI one of my very favorite rifles, of all my rifles, not just compared to the 7mm mag-- and I love overbores!

[helotaxi]

Other than energy on the target, weight has nothing to do with it. You can predict the flight of a bullet without knowing anything about the bullet's weight, in fact. All you need to know and all that matters WRT bullet trajectory is muzzle velocity and ballistic coefficient. Despite what seems intuitive, bullet weight doesn't have anything to do with wind drift.

The reason that the 45-70 was shootable to those ranges with the low BC bullets that they shoot is that the low muzzle velocity means that the bullet doesn't lose that much velocity as it goes downrange. Wind drift is proportional to velocity loss. An interesting exercise in that vein is running the wind drift numbers on the .300 Blackout shooting a subsonic 220gn SMK.

[FUBAR]

The reason that the 45-70 was shootable to those ranges with the low BC bullets that they shoot is that the low muzzle velocity means that the bullet doesn't lose that much velocity as it goes downrange.

What???

Some of those old 250 or so grain bullets have about 3000 fps muzzle velocity and are down to 600fps by the time they reach 1000 yards and in the 500fps range at 1200 yards.

In fact they have lost Half their muzzle velocity in the first 300 yards!

Ok if we forget "weight" as a factor in windy conditions, I understand the argument. There is no way however to exclude "weight"--without a certain sectional density the projectile will never have a design that supports the BC nor withstand the launch....

[handirifle]

To my knowledge there never has been a 45-70 round loaded with a 250gr bullet at 3000fps. Barnes has an X bullet that weighs 250gr but it is the only one that I am aware of.

The 45-70 was so effective, BECAUSE of the bullets weight. An object in motion, tends to stay in motion. Newtons law, and thus the heavier the object is, the harder it is to stop. Velocity is a factor, but if velocity and BC was the end all, then one would be unable to explain why a 400gr (typical bullet weight) 45-70 bullet will penetrate 8-10 times as many water filled milk jugs of say a 243 and a 100gr bullet. It's called momentum.

There is a documented test of the 45-70 at over a mile, where a 400gr bullet at around 1300fps MV, was fired into a 4" thick wood target over a mile away. The bullet went completely through the target and over a foot deep in the sand behind it. Which is easier to stop, a train doing 30 mph, or a car doing 60?

Slam a car doing 60 into a 5000lb car and it will stop in a few feet after impact, slam a train doing 30 (or 20 for that matter) into a 5000lb car and 1/2 to one miles later it will stop. Momentum!

[Panozguy]

You guys are getting over my head quickly, so I'll just keep it simple. Of all the people I know who shoot at distance, not one of them shoots a .270 at the range - and we're talking a lot of people here. .308? Sure, plenty of 'em. 7mm, 6mm, 6.5mm variants? Sure, plenty of them. Even .223. But not ONE single .270.

Buy what you want, but there must be some reason for this...best of luck, OP.

Edit - I mean long distance target practice, not hunting. Punching paper or steel, which I believe was the original purpose of this thread.

[FUBAR]

Your right, there is only a couple and we are not talking lever guns with short barrels... even with a "Quigley" type Sharps rifle, 45-110 & 34 inches of barrel, no one would use a 250 gr bullet, even though the could get amazing muzzle velocity.

My point was even with a 45-?? it takes mass/weight/SD, around 400 gr, to support the design/BC and maintain velocity....

My 6-284 uses a 1-8 twist barrel by design, in order to use the highest weight/BC bullets made, and it is no fluke that the 117 gr DTAC has the highest BC (600)

However drop the powder and velocity a bit and my 6-284 is routinely out shot by the other more common Benchrest 6mm's at 1000 yards

The above fact is not an issue for me because I'm not concerned with fractions of an inch at 700 yards, I would rather have SD and energy, but that's just me

[358Hammer]

"Even .223. But not ONE single .270."

Fubar has a wonderful example: There are a number of ways to accomplish a given task and his is just one way. When the 270 first came out it was one of the fastest kids on the block and writers with sharp pens made it something even better than it was. Bullet technolgy was way behind back when the 270,308 Norma Mag and the various fast cartridges were wounding game because of inferior bullet construction..

Technology and knowledge advanced and for various reasons (money) high BC bullets for the 270 Winchester were down on the money scale and the screaming 270 ballistics just kind of got put on the back burner when the 300's were eating up the long range circle.

When the first 223 won a long range match I am sure it was a novelty and many just smiled thinking it was a fluke. When that same gun did it again some started paying attention. Trends start and stop in the winners circle. When we started improvong that little 6 BR case there was a reason. Then someone took that little case concept and here was the 6.5 X 47 Lapua.

Now that the 270 has the bullets to compete it just needs someone to believe in it and start competing with it.

Neal

[Panozguy]

"Even .223. But not ONE single .270."

Fubar has a wonderful example: There are a number of ways to accomplish a given task and his is just one way. When the 270 first came out it was one of the fastest kids on the block and writers with sharp pens made it something even better than it was. Bullet technolgy was way behind back when the 270,308 Norma Mag and the various fast cartridges were wounding game because of inferior bullet construction..

Technology and knowledge advanced and for various reasons (money) high BC bullets for the 270 Winchester were down on the money scale and the screaming 270 ballistics just kind of got put on the back burner when the 300's were eating up the long range circle.

When the first 223 won a long range match I am sure it was a novelty and many just smiled thinking it was a fluke. When that same gun did it again some started paying attention. Trends start and stop in the winners circle. When we started improvong that little 6 BR case there was a reason. Then someone took that little case concept and here was the 6.5 X 47 Lapua.

Now that the 270 has the bullets to compete it just needs someone to believe in it and start competing with it.

Neal

Point taken. And for the record, I actually hope it works! I'm not in any way hating on the .270. I would happily own and shoot one at the range if it proved to be superior to what I already own.

[helotaxi]

To my knowledge there never has been a 45-70 round loaded with a 250gr bullet at 3000fps. Barnes has an X bullet that weighs 250gr but it is the only one that I am aware of.

The 45-70 was so effective, BECAUSE of the bullets weight. An object in motion, tends to stay in motion. Newtons law, and thus the heavier the object is, the harder it is to stop. Velocity is a factor, but if velocity and BC was the end all, then one would be unable to explain why a 400gr (typical bullet weight) 45-70 bullet will penetrate 8-10 times as many water filled milk jugs of say a 243 and a 100gr bullet. It's called momentum.

There is a documented test of the 45-70 at over a mile, where a 400gr bullet at around 1300fps MV, was fired into a 4" thick wood target over a mile away. The bullet went completely through the target and over a foot deep in the sand behind it. Which is easier to stop, a train doing 30 mph, or a car doing 60?

Slam a car doing 60 into a 5000lb car and it will stop in a few feet after impact, slam a train doing 30 (or 20 for that matter) into a 5000lb car and 1/2 to one miles later it will stop. Momentum!

Bullet weight is captured insomuch as it matters for exterior ballistics in the bullet's BC. BC is made up of two components: sectional density (SD) and form factor. Weight only matters as a ratio with frontal area. That is the definition of SD. If you don't believe me run a ballistics curve on a bullet of your choice and then make no other changes to the inputs (same BC and velocity) and reduce the bullet weight to 10gn. You'll notice that other than energy absolutely nothing changes with regard to bullet drop or wind drift. Two bullets of the same BC fired at the same velocity will fly exactly the same even if one weighs 200gn and the other 50.

The same principles apply when examining terminal ballistics and penetration. Target penetration is determined by SD and velocity. Bullet expansion affects SD, so the rate of bullet expansion affects penetration. That means to get a meaningful comparison between bullets you need bullets of the same construction that will expand the same. Assuming that you have that, bullets of the same SD impacting with the same velocity, will penetrate the same regardless of weight.

Momentum matters, but it is certainly isn't the only factor. You have to account for resistance. That's why SD matters. Resistance/drag is proportional to the frontal area of the projectile. SD corrects mass for frontal area so you're comparing apples with apples. Why flies farther, a javelin or a shot put? The shot weighs more. Which would you rather be hit with assuming that they're traveling the same speed (given "neither" would be my choice, but anyway). Man quit hunting with thrown rocks once he developed the spear. He could throw the spear farther and it certainly penetrated more when it hit something, even though it weighed less.

[sortafast]

No free lunch. With the velocity comes the recoil. No way around it. That said, the 7mm Mag isn't a very hard kicker anyway. Not something I'd want to settle down behind for a long day at the bench but 20-40 rounds with a good recoil pad, even with a really light rifle aren't uncomfortable.

On the -06 format, don't forget the 6.5-06. For a given BC and SD, 6.5 bullets are going to be lighter than their 7mm counterpart meaning that velocity stays about the same, despite the reduction in bullet base area, and recoil is reduced. I'm in the 280 AI camp personally simply because I already keep 7mm bullets on hand (though my next project is my long range hunting rifle in 7 WSM) but if you're not already committed to a certain caliber, it's worth a thought.

I am not worried about recoil. The rifle is going to weigh 10lbs or better and I am going to run a brake and eventually a can on the end. I am pretty sold on the 280AI right now. Still kind of want to do a 30-06AI just to see what kind of difference I can get with it and how far I can get it to stretch it's legs. But I have been told that once you do one Savage you start working on another, not that its a bad thing, other than keeping my wife happy.

[handirifle]

helo taxi
I agree in part with your statement. The part I do not agree with is the comparison of a 200gr and a 10gr bullet with the same BC is virtually impossible in the firearms world. A 10 gr bullet with the same BC as a 200gr bullet, say in 30 cal, would be the shape of a sewing needle

Again, I will match a 400gr .458 bullet at 1600fps against a 30-06 180gr bullet, any day of the week when it comes to punching through gallon jugs of water. Use a FMJ 30 cal bullet so expansion do not interfere with penetration. I have seen it done MANY times, you'll see the .458 bullet pass through 10-15 jugs and the high velocity, high BC bullet will be lucky to go through 6.

The big slow heavy bullets DEFY the "normal" theories of what makes a bullet penetrate.

You want examples, go to the http://www.garrettcartridges.com/luposafaris.htmlGarrett Ammo website and click on Lupo Safari's link. Read what the lowly 45-70 does to animals like the Rhino, with a bullet traveling at under 1600fps. There is no way in the world a 30 cal bullet at 2700fps and with a 550 BC, and 200gr weight would even come close.

[handirifle]

I am not worried about recoil. The rifle is going to weigh 10lbs or better and I am going to run a brake and eventually a can on the end. I am pretty sold on the 280AI right now. Still kind of want to do a 30-06AI just to see what kind of difference I can get with it and how far I can get it to stretch it's legs. But I have been told that once you do one Savage you start working on another, not that its a bad thing, other than keeping my wife happy.

I think the 280 AI is a great choice for what you want, whether it's paper or elk. Good bullet selection, good cartridge. The AI was standardized because there is no worry of overloading rifles originally chambered in 280.

[helotaxi]

helo taxi
I agree in part with your statement. The part I do not agree with is the comparison of a 200gr and a 10gr bullet with the same BC is virtually impossible in the firearms world. A 10 gr bullet with the same BC as a 200gr bullet, say in 30 cal, would be the shape of a sewing needle

Merely an extreme example to demonstrate that weight itself has no bearing on external ballistics. If you want a real world example, take the .224 53gn Vmax fired at 3400fps from a .223 and compare it to the 75gn Hornady HP fired from a .243 Win again at 3400fps. The BC's of the two bullets are almost identical and they are fired at the same velocity and will have the nearly identical trajectories dictated by their difference in BC even though they are different weights. Likewise, compare the 105gn Hornady BTHP from a .243 @ 3000fps to the 178gn HPBT from a 300 Win Mag also @ 3000 fps. They have the same BC and will fly exactly the same despite the 70% difference in bullet weight.

Again, I will match a 400gr .458 bullet at 1600fps against a 30-06 180gr bullet, any day of the week when it comes to punching through gallon jugs of water. Use a FMJ 30 cal bullet so expansion do not interfere with penetration. I have seen it done MANY times, you'll see the .458 bullet pass through 10-15 jugs and the high velocity, high BC bullet will be lucky to go through 6.

The big slow heavy bullets DEFY the "normal" theories of what makes a bullet penetrate.

You want examples, go to the http://www.garrettcartridges.com/luposafaris.htmlGarrett Ammo website and click on Lupo Safari's link. Read what the lowly 45-70 does to animals like the Rhino, with a bullet traveling at under 1600fps. There is no way in the world a 30 cal bullet at 2700fps and with a 550 BC, and 200gr weight would even come close.

The bullets defy nothing. This is physics, not "notions". You're ignoring the most important part which is for the comparison to be valid, the bullets have to be of like design and construction. The large monolithic solids don't expand. In reality, the 150gn FMJ from a .308 does. Its spitzer design causes it to yaw when it hits the milk jugs and the bullet then usually rips apart at the cannelure. The yaw changes the sectional density drastically because now the side of the bullet is the frontal area. Fragmenting changes it even more drastically since now each fragment is a "bullet" unto itself with a very low sectional density. In contrast, the .458 solids, don't expand and their blunt shape also keeps them from yawing. The result is a constant SD and deep penetration. It performs exactly as the physics dictates that it would. If you had a similar .308cal bullet, shape and construction, with the same sectional density, it would weigh less (180ish grains to have the same SD as a 400gn .458 slug) but impacting at that same 2700 FPS, it would penetrate deeper.

Whether you agree or disagree, those are the facts. Don't just take my word for it. Do some research. Ge a copy of Applied Ballistics for Long Range Shooting. Bryan Litz, the chief ballistician for Berger Bullets, breaks all this down into simple terms. It's a very enlightening read from a guy with not just credibility in the shooting world but also with an aeronautics, physics and engineering background to back up what he's saying.

[r3dn3ck]

I was the one that said velocity is all that matters and I was perhaps a little heavy handed in my phrasing on the matter but the fact of the matter is that strictly speaking about drop, the more velocity retained over x period the lower the drop period. Helotaxi has done a fabulous job in explaining the physics behind this to everyone for me which I thank him for. All else being equal a bullet that retains velocity longer time will make it not only further down the road but be affected by gravity exactly the same as a slower bullet over the same period time. A slow bullet and a fast bullet get to different horizontal distances over X period time. During that time span they will drop the exact same amount, they will simply have gone different distances before doing so.

The basic ballistics equation evaluates and then integrates complex data sets. If you really look at the equations and apply the various algebraic properties to the elements of it such that you isolate what it's really doing at any one place, it is mapping the Horizontal-position@time slope against a Vertical-position@time slope (and this is why bullet time of flight is a part of the output data set) and to then display nothing more than gravity's effect on vertical position based on roughly 32ft/s/s acceleration given the time of flight. The particular horizontal distance achieved over period time X is only relevant as an output value when analyzed against the vertical position at the same time. If the calculation was going to try to be precise it would have to take several other factors into consideration which most calculators don't more or less because it can't easily be done with the sorts of vague generalities and coarse rules of thumb we already use still in play. Yes, there are phenomena like spin-drift and the tendency of certain bullet shapes to fly in a very different attitude with respect to their direction of travel at long distances but those as well are not easily worked up into a calculator you can use on the web.

There is a small subset of participants in this thread that have managed to confuse terminal ballistics with external ballistics and momentum with a number of things. To those folks: please try to keep the thought muddle under control and you'll find that the concepts are then very easy to fully understand with only a modest recollection of high school algebra and physics classes.

I am not a ballistician but I did sleep at a holiday inn once and I used to be a math geek. Thankfully I've forgotten all the really fun parts of math and have gone on to better things, like shooting debris just to see if I can hit it.

OP: none of this is relevant to your needs or question. Basic advice, if you want to use a .270 then stick with bullets on the heavier end of the available weight options and plan to spend on those high-BC bullets which will maintain velocity better over time and make your come-up values smaller. Handloading will almost certainly be required to get the most out of your time at 1K yards. Don't hunt at that range with that gun. Yes it's lethal, no it's not a good idea or ethical by modern standards.

EDIT: for those that want to do the math, here's a nice page showing all the bits and where they're working and HOW they're working. http://www.grc.nasa.gov/WWW/k-12/airplane/flteqs.html

[FUBAR]

Bullet weight is captured insomuch as it matters for exterior ballistics in the bullet's BC. BC is made up of two components: sectional density (SD) and form factor. Weight only matters as a ratio with frontal area. That is the definition of SD. Two bullets of the same BC fired at the same velocity will fly exactly the same even if one weighs 200gn and the other 50.

We got into this mess because no one use to make high BC bullets for the .270 Win, but that is changing.

The bullets only fly the same if all the other variables are the equal for the two given calibersbecause they can't be the same caliber!

On the surface many of your statements are correct, but then you start over explaining it, and I think it's because you get hung up on the semantics, and many of your statements are misleading...

Sectional Density is:

w/d squared

Weight of bullet in pounds
Bullet diameter squared


For the above it's weight (in pounds) contained in each square inch of frontal bullet cross section....

In the vernacular--a long bullet has a bunch of SD

Again, you are correct if you have two bullets with the same BC they will fly the same given the same variables: However, you can't there without mass/material/weight, whatever you want to call it, to create the SD in any given bore size.

To say it another way, you are again correct that mass/weight does not equal SD or BC, but you can't have SD/BC wihout mass/weight:

In other words, in .243 cal a 55 gr bullet can never have the same BC as a 110 gr bullet, but just because it's a 110 gr bullet does not mean it will have a high BC ( vernacular again, long skinny vs. short fat )

With all that crap said, my point is still the same:

If he wants to shoot a .270 long range, it's capable of doing it, esp. with new designs in bullets for the .270....

He shoud study and understand all the things in principle, then put them to practice! "In Vivo" vs "In Vitro"

I say make the very best ammo he can for the given barrel length/twist and enjoy the accomplishments!

[r3dn3ck]

^^^ +1

[thomae]

I recently became fascinated by an article on the 6.5mm Creedmoor due to it's 1000yd range. The Creed is basically a 260. Will the 260 reach that far? I have a 270 currently and so I was wondering if the 270 can reach 1000 as well? A buddy told me a few yrs ago that the 270 is the lngest flattest shooter. Is this true?

A. There will always be debate, some informed, some ignorant, on what caliber is the longest flattest shooter and similar issues. New wildcats designed toward that goal are developed with amazing regularity. {My personal choice would be a 50 BMG necked down to shoot a .17 caliber 220 grain bullet - Ok, that's a joke...}

B. It appears that the major posters in this thread agree that one can safely say that the 270, especially when handloaded with a relatively heavy, high BC projectile, can reach out to punch paper or hit a gong at 1000 yards. Is it the perfect or ideal or best cartridge for this purpose? Probably not...but it still can do it.

I think we have answered the OP's question.

For what it's worth, I have never hit anything at 1000 yards because a) I don't have anyplace to shoot that kind of range, and b) If I were to try at that distance, I firmly believe the auto-aiming-and-trigger-actuation-device would not work out very well.

Back in the day, however, with the right equipment, I could launch a 2000 pound projectile from 300 feet in the air, while going 300 knots and place it within 15 feet of a designated target point. That was fun!

[r3dn3ck]

^^^ and not one ****ed bit less impressive than ringing steel with a rifle at any particular range.

[helotaxi]

The bullets only fly the same if all the other variables are the equal for the two given calibersbecause they can't be the same caliber!

Actually it's pretty easy to find bullets of different weights in the same caliber with the the same BC. Launch those at the same velocity, they fly the same. It's just BC and velocity, nothing else matters. Remember that SD is only a part of BC. You can't ignore form factor. A lighter VLD can easily have a better BC than a much heavier round nose in the same caliber.

For the above it's weight (in pounds) contained in each square inch of frontal bullet cross section....

In the vernacular--a long bullet has a bunch of SD

Complete disconnect between the first statement, which is true and which I've stated, and the second which is not true and relies on a logical fallacy to seem true. Length and SD are not related. Weight and caliber are all the determines SD. Form factor and material determine length. A 155gn Amax is longer than a 220gn round nose (both in .308) but the round nose has a higher SD. A 50gn Barnes Varmint Grenade is a great deal longer than a 50gn Vmax, but they have the same SD.

Again, you are correct if you have two bullets with the same BC they will fly the same given the same variables: However, you can't there without mass/material/weight, whatever you want to call it, to create the SD in any given bore size.

Not sure what you're trying to say here, but it seems that you're ignoring form factor again. With the proper form factor you can get a quite high BC in a relatively lightweight (even for caliber) bullet. The 53gn Vmax is a good example of this. It has a higher BC than the 60gn Vmax. Look at the BCs of some of the Berger VLDs as well. Even within these really efficient bullets within the same caliber, the heaviest bullet doesn't always have the highest BC.

To say it another way, you are again correct that mass/weight does not equal SD or BC, but you can't have SD/BC wihout mass/weight:

In other words, in .243 cal a 55 gr bullet can never have the same BC as a 110 gr bullet, but just because it's a 110 gr bullet does not mean it will have a high BC ( vernacular again, long skinny vs. short fat )

Actually, for a given caliber weight DOES completely determine SD. But, again, you're ignoring form factor, because the 55gn .243 Vmax actually has a higher BC than the 100gn Hornady round nose. There are two variables in the equation for BC and they are equally weighted. SD is only half the total.

[FUBAR]

Actually it's pretty easy to find bullets of different weights in the same caliber with the the same BC. Launch those at the same velocity, they fly the same. It's just BC and velocity, nothing else matters. Remember that SD is only a part of BC. You can't ignore form factor. A lighter VLD can easily have a better BC than a much heavier round nose in the same

Complete disconnect between the first statement, which is true and which I've stated, and the second which is not true and relies on a logical fallacy to seem true. Length and SD are not related. Weight and caliber are all the determines SD. Form factor and material determine length. A 155gn Amax is longer than a 220gn round nose (both in .308) but the round nose has a higher SD. A 50gn Barnes Varmint Grenade is a great deal longer than a 50gn Vmax, but they have the same SD.

Not sure what you're trying to say here, but it seems that you're ignoring form factor again. With the proper form factor you can get a quite high BC in a relatively lightweight (even for caliber) bullet. The 53gn Vmax is a good example of this. It has a higher BC than the 60gn Vmax. Look at the BCs of some of the Berger VLDs as well. Even within these really efficient bullets within the same caliber, the heaviest bullet doesn't always have the highest BC.

Actually, for a given caliber weight DOES completely determine SD.
But, again, you're ignoring form factor, because the 55gn .243 Vmax actually has a higher BC than the 100gn Hornady round nose. There are two variables in the equation for BC and they are equally weighted. SD is only half the total. Did

Wow you need to go back and re-read what I wrote.

I took exception to your statement in post #28 "Other than energy on the target, weight has nothing to do with it" That statement is completely incorrect, for each specific caliber weight is a huge part of it!

I will re-state it all in simple terms:

In the same caliber it takes weight to design the highest BC possible (form factor).

The "vernacular, long skinny" comment was humor not meant to be taken literally, it's too general.

Given the total context of my statement, my point was-- given the correct design (form factor) the highest BC bullet will weigh at the higher end of the weight spectrum for the specific caliber.

The two bullet ballistic example was directly related to your 50 grain and 200 grain example.

I said: Your ballistic "fly the same" example has to be different calibers--There is never a 50 grain bullet and a 200 grain bullet with the same BC in the same caliber.....

Never said SD was the total deciding factor in BC, just said you cannot get the "form factor" design without a high SD (for a specific caliber).

Think Semantics is getting in the way again, many times you can insert "form factor" with design...


Whew!

I'm done with this discussion...

Thanks for the debate,

[Mach2]

.Helotaxi said(quote) Two bullets of the same BC fired at the same velocity will fly exactly the same even if one weighs 200gn and the other 50.(end quote)

Mach2 replies:
Im trying to follow you guys. So here goes. If you drop a 5lb cannon ball from 5 feet it will land at the same time as a 10 lb cannon ball is fired from a cannon 5 feet high no matter what amount of powder used. Assuming the cannon is aimed parallel to the ground. Is that correct? I think I heard that in physics. Unfortunantly I was hungover in that class.

[rusty815]

.Helotaxi said(quote) Two bullets of the same BC fired at the same velocity will fly exactly the same even if one weighs 200gn and the other 50.(end quote)

Mach2 replies:
Im trying to follow you guys. So here goes. If you drop a 5lb cannon ball from 5 feet it will land at the same time as a 10 lb cannon ball is fired from a cannon 5 feet high no matter what amount of powder used. Assuming the cannon is aimed parallel to the ground. Is that correct? I think I heard that in physics. Unfortunantly I was hungover in that class.

That would be correct under perfect conditions, i.e. in a vacuum. In real world conditions, atmospheric drag becomes a factor. This partially explains why to have a high BC bullet, you generally need to have a heavier for the caliber round; the extra weight adds momentum to the bullet and that, along with a low drag profile, equals a high BC for the bullet.

[helotaxi]

Never said SD was the total deciding factor in BC, just said you cannot get the "form factor" design without a high SD (for a specific caliber).

My only issue is that your statements were incomplete and incredibly misleading because of it. Form factor is totally independent of SD. Barnes bullets and all the other monolithic copper designs prove this. They have excellent form factor but lack SD and the BC suffers. My whole point is that you can't look at bullet mass alone and say "this bullet will resist wind better". I see that myth/misunderstanding promulgated all over the web. Unless/until all other variables are held constant, including caliber, weight means nothing. It might be a by product of design, but is not usually a goal in and of itself. I see all too often people claiming that a .30cal will resist wind drift better than a .243 because the bullet is heavier and that simply isn't true. All that matters about bullet weight with regard to how it sheds velocity and resists wind drift is captured in the bullet's BC. I used the 50gn and 200gn example as extremes just to make a point. Yes, we all know that you're highly unlikely to find a 50gn bullet and a 200gn bullet in the same caliber that have the same BC, going through the exercise with a ballistic calculator does show that weight alone doesn't have any bearing on anything. All you need to calculate ballistics is velocity and BC.

[FUBAR]

.Helotaxi said(quote) Two bullets of the same BC fired at the same velocity will fly exactly the same even if one weighs 200gn and the other 50.(end quote)

Mach2 replies:
Im trying to follow you guys. So here goes. If you drop a 5lb cannon ball from 5 feet it will land at the same time as a 10 lb cannon ball is fired from a cannon 5 feet high no matter what amount of powder used. Assuming the cannon is aimed parallel to the ground. Is that correct? I think I heard that in physics. Unfortunantly I was hungover in that class.

Your right, and at a given point each bullet drops the same.

We are talking about how BC effects trajectory, and what effects wind and atmosphere will have on rifles/projectiles that have been set up to arc the shot and how much arc it needs to get to a given point, (point of aim and point of impact)-- that's assuming the round has enough energy to get there.


My point is that right now given design limitations, the 50 grain bullet and the 200 grain of the same BC have to be from different calibers.

Plus as stated by Rusty, in the fly the same theory the varibles have to be exactly the same. He used "in a vacuum" and that accounts for the atmospheric variables....

But it's all an in theory vs in practice argument and in practice wins right now..Ballistic programs do not produce empirical data!

I can't control the variables enough to get my new 338 Lapua AI to shoot as well at 1000 yards as my 6mm XC (even if I shoot the same BC bullet).

Now we are talking doing it over and over again while trying to hit the first hole in the target. Again in theory it's assumed that the large bore/large case Lapua does not burn the powder constantly enough to control the point of impact, but it's theory.

In the Benchrest 1000 yard world the small bores/cases win, look at the 1000 Benchrest champs for the past 20 years.

Now "point blank range" for a rifle fired flat, without arc, is a completely different matter