270 and Long Distance

[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" :cool:

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 SDComplete 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 :cool:

[helotaxi]

Chances are that your issue is with bullet dispersion from the rifle itself, not what happens after the bullet leaves the bore. The rifle and the load are the variables that you're having trouble controlling, not the flight of the bullet itself. With the right powder and bullet combination, the .338 LM burns the powder quite consistently, you just have to find that combination and hope that it matches the harmonics of your barrel.

[FUBAR]

Chances are that your issue is with bullet dispersion from the rifle itself, not what happens after the bullet leaves the bore. The rifle and the load are the variables that you're having trouble controlling, not the flight of the bullet itself. With the right powder and bullet combination, the .338 LM burns the powder quite consistently, you just have to find that combination and hope that it matches the harmonics of your barrel.

It's possible, not my theory, it's the theory of some of the best shooters in the world-- others theorise it's recoil and barrel harmonics... None of the largebore magums have won the 1000 yard Benchrest comp yet....

Just used my Lapua as a general example...The very best rifles/shooters in the world have the same type issues.

[helotaxi]

The current world record holder in 1000yd benchrest is a .300WSM.

Weight counts, right? For a given barrel weight, the smaller bore is going to be more rigid. More rigid means less barrel harmonics to deal with and that means less dispersion from the barrel from the getgo. After the bullet leaves the bore, it's purely physics and aerodynamics. Same BC, same velocity, under the same atmospherics means exactly the same flight path.

The large-bore magnums also kick like a mule and since most of the comps don't allow muzzle brakes and limit the weight of the rifles. That limits who's willing to shoot a large bore magnum in long range competition. Trigger time counts. Fatigue matters. A rifle that is abusive to shoot decreases rounds fired before fatigue becomes a factor. That limits practice and makes such a rifle impractical and uncompetitive over a long course of fire.

[Mach2]

Well, the reason I started this thread about the 270Win is that I already had a one and wondered if it was worth spending money on a 260Rem since there is only .010 difference in caliber. I wondered if I could achieve the same thing with a 270 as I could with a 260. It seems such a tiny difference
(.010)The amswer seems to be that I could or nearly could achieve the same result if I studied and worked at it. But at long distance I may achieve what I want easier and sooner with a 260 from the standpoint of a novice tying to get somewhere..

[FUBAR]

Way off of the OP:

30 calibers use to rule, and the may again but--

The highest IBS single high score was set by Sally Bauer with a 6-6.5 Lapua Improved http://bulletin.accurateshooter.com/2012/09/sally-bauer-sets-pending-ibs-1000-yard-hg-score-record/

30 calibers & 7mms make up about 20% of the shooters for 2012

The Overall IBS Grand Champion for 2012 is Mark King shooting a 6mm Dasher
http://internationalbenchrest.com/results/long_range/2012/WhiteHorse/Nationals/WhiteHorseNC.php

I think someone was shooting a 338 Norma in the Heavy gun division for the 2012 National Championship, but Heavy Gun was won with a 6mm Dasher

Ballistic programs work off of algorithms and data input, they are "trajectory models" they do not produce empirical data....

Different makes can and do produce different information using the same bullet

[helotaxi]

Ballistic programs work off of algorithms and data input, they are "trajectory models" they do not produce empirical data....


However, with accurate data, the algorithms have proven to be amazingly accurate. The problem is that getting accurate data is impossible. Variations in how the bullet leaves the bore will alter the realized BC of the bullet as well. Since no two rifles shoot exaclty the same, everything is "theoretical". Since you can't exactly measure the wind or air density over a 1000yd range, you also can't attribute differences in the outcome to the cartridge, the caliber, the rifle or anything else because you can't isolate the external variables. The good news is that professionals who have the time and resources to test a lot of bullets and loads and measure their performance extremely precisely have done so. Their results have created the models that the algorithms are built on and those models are built using empircal data.

[Panozguy]

Well, the reason I started this thread about the 270Win is that I already had a one and wondered if it was worth spending money on a 260Rem since there is only .010 difference in caliber. I wondered if I could achieve the same thing with a 270 as I could with a 260. It seems such a tiny difference
(.010)The amswer seems to be that I could or nearly could achieve the same result if I studied and worked at it. But at long distance I may achieve what I want easier and sooner with a 260 from the standpoint of a novice tying to get somewhere..

Go with what you want, Mach 2. But before you make the leap, look into .260 and the various 6.5mm variants. I wouldn't want to end up with 2 years of work and a bunch of money that you couldn't get rid of easily. But everybody does things for different reasons, so if that's your game, go with it.

Most importantly - have fun and go shoot!

[helotaxi]

The sole limitation on the .270 is bullet selection. Even the VLDs from Berger give up a lot of BC to the other calibers because there has never been a demand for long range bullets in .277cal. If you have a .270 already, something to consider would be a 6.5 or 6mm-06 or a .280 AI. They'll take advantage of the long action and get you into a caliber that does have a wealth of good long range bullets available.

[FUBAR]

Mach2:

I think you might be surprised with what you can do with a .270 now days....

However you will love a .260 in the appropriate configuration for Longrange shooting/hunting-- a lot of theory and practice has went into developing the .260 family into Longrange shooters.

Don't be confused by our rambling arguments, even though there is a direct correlation between bullet weight and BC, that's academic. (visit the Berger link below and make your own decision)

Right now BC and velocity alone does not guarantee you a win...In the IBS Nationals many of the larger calibers .30 & 338 were shooting higher BC bullets with equal or higher velocity than many of the 6mm rifles that scored higher than them. It's the old in theory vs in practice, and in purely sincetific terms it's an anecdotal argument....however it's the same basic argument that supports your .260 decision;)

http://internationalbenchrest.com/results/long_range/2012/WhiteHorse/Nationals/WhiteHorseNC.php

BC in simple terms is mass, diameter, and drag coefficient, here is a link to a basic starting point for the formula(s). It outlines the relationship between SD and Form Factor....

http://en.wikipedia.org/wiki/Ballistic_coefficient

Then move on to Bryan Litz, you can read the articles and decide if you want the book....I highly recommend.

http://www.appliedballisticsllc.com/index_files/Book.htm

And if you don't have ballistics program, get one, more than one. Also it's good to understand things like the difference between G1 vs G7, but in general terms use G1 for more round nose designs and G7 for VDL type designs. Note: the previous statement is overly simplified, but that hint will get you started on the path to understanding ballistic models...

Since Bryan and Berger are referenced, I provided a link to Berger target bullets, and it has a nice comparison link for their other bullets.

helotaxi is correct in his statement "all you need to know to calculate ballistic trajectory is velocity and BC" but it's misleading, the program inherently knows data about the weight, SD, and form factor etc. (reference the formula)

In other words the data has already been inputed/stored in the ballistic programs database i.e. a .243 700 BC bullet is a 117 grain DTAC . Even when a custom BC is entered the ballistics program extrapolates the results based on known, stored information.

As helotaxi said weight alone does not matter....
I originally said in simple terms that it's weight, velocity & BC, and it's basically a correct statement....but I admit I could drop the "weight" because I inherently know that the weight falls at the high end of the BC/weight spectrum , if I know the BC :cool: The reverse is not true, knowing the weight, will not provide an extrapolated BC.

Note that in each caliber listed in the Berger Target bullet link, the highest weight bullet is also the highest BC bullet. That's not accidental, it's by design, and in the vernacular "they are the long pointy ones (that's the form factor, formula stuff)

http://www.bergerbullets.com/Products/Target%20Bullets.html

[helotaxi]

There is no direct relationship between SD and form factor, unless you're using the BC as a constant. SD is nothing more than weight related to the caliber. Form factor is the shape of the bullet. For example, take two bullets of the same caliber with the same form factor, one of monolithic construction and the other a standard copper jacketed lead core bullet. They will have different SD's because of the different densities of copper and lead. As a result they will have a different BC as well.

You can use a program that doesn't know the first thing about the bullet except the BC that you enter and the velocity and it will calculate the trajectory. The weight, through the SD, is captured in as much as it matters in the BC of the bullet. BC is all that matters as far as the bullet itself is concerned. Digging any deeper is really just complicating things.

Read Litz's book. I would say that it is the single best reference out there about what matters written in terms that a lay person can understand.