I just punched in my 308 Win data (175SMK @2600fps) into my Iphone Ballistic AE program and am viewing the results for G1 and G7. At 600 yds, the G7 is showing about 2.5" more drop and more wind drift than the G1 model. Which model would you believe, and tends to be more accurate? Eventually, I'm going to check the results by shooting, but I was wondering what you guys felt about the differences between the two. Thanks-
- Thread starter Fatelvis
- Start date
For all boat tail rifle bullets the G7 is the way to go. Try googling the dimensions for the G1 and G7 bullets, you'll see that they have flat base and boat tail base respectively. The thing that's the hardest to get right is the BC, whichever standard bullet you choose. What BC did you punch in? I have from Brian Litz's book (in which he tested BC's ) that a true measured G7 BC for the 175 SMK is: 0.243
--- aim small miss small ---
--- aim small miss small ---
Thank you Woo. But if the G7 is better for boat tail bullets, why is it showing MORE drop (about 2.5" @ 600yds) than G1? Shouldnt it take into consideration the better ballistic profile, and show less drop? And yes, I used the Litz listing for the bullet, which shows .243 BC.
Hm, that is odd. Well since G7 and G1 are like apple's and oranges, its hard to scale back and forth. I would guess that the G1 BC is just inflated so its way off the mark. I would just trust the G7 from Litz. I've not tested the .308s but the 6mm BC's from him are giving me first round hits on 1000 yards steel (well second round in truth, not counting the "cold bore" shot, although sometimes) with the 115 DTAC and the 105 Amax.
--- aim small miss small ---
--- aim small miss small ---
Either work. I have been using G1 for years and it's never been off more than .2 mils at 1000 which is about 7". Might sound like a lot but it's not. G7 has become more popular over the past few years and it does work but it doesn't work any different than the G1. Just two ways to get there.
Two different ways of expressing the same thing. What's better: Inches or centimeters? Doesn't matter because it's the same measurement.
I use G1 and I input multiple BCs if I can, or calibrate my ballistics program if I can't. Both will get you there accurately.
Sent from my iPhone using Tapatalk
I use G1 and I input multiple BCs if I can, or calibrate my ballistics program if I can't. Both will get you there accurately.
Sent from my iPhone using Tapatalk
duplicate
Last edited:
They're not the same. It's like asking if an inch is 25mm or 25.5mm. Both are wrong, but one is wronger, and both might be close enough. For the SMK 175 G7 is better. But as others mentioned, at 600 yards the difference is academic.
G1 or G7?
They're not the same because a BC is not a linear measurement and it is derived differently. But you know what I meant. And G7 isn't 'better' for a 175SMK.
Yawn,
you have an iPhone, use both and see which one works... It's just a starting point and not some magic number. The more you shoot the more you realize every rifle is different and no one number can be expected to fit perfectly. You do the exact same amount of work regardless which one you choose. Remember he tested it with his gun, not yours. Adjustments maybe necessary.
Theses are averages, they're designed to get you close then to be fine tuned for your system. It's not a one number fits all.
you have an iPhone, use both and see which one works... It's just a starting point and not some magic number. The more you shoot the more you realize every rifle is different and no one number can be expected to fit perfectly. You do the exact same amount of work regardless which one you choose. Remember he tested it with his gun, not yours. Adjustments maybe necessary.
Theses are averages, they're designed to get you close then to be fine tuned for your system. It's not a one number fits all.
I know what you meant, but there are people who don't. Just clarifying.
Better means a more accurate prediction, not better performing. The bullet does what it does. The drag function just attempts to predict what the bullet it will do. You could use the drag function of a sphere to calculate the trajectory of that bullet, and it would work (poorly). It just wouldn't be as accurate as a G1, which won't be as accurate as a G7. The difference between the sphere and G1 will be large. The difference between G1 and G7 is very small. None of them will predict the bullet's behavior exactly.
Last edited:
Hm. I see another game of semantics being played. Is the G7 more accurate? ... Depends on what you mean by accurate. The G7, G1, sphere, and many other "standard" bullets are just a baseline drag vs mach curve. The BC scales your current bullet to the standard bullets drag profile to extract a drag coefficient for each time step as the program walks through the trajectory and calculates deceleration. The idea is to use a drag profile for whichever standard bullet behaves closest to your current bullet. Therefore if you are using a HPBT or similar, the G7 makes more sense than the G1 because the G7 is kind of a HPBT shape while the G1 is flat base. The drag profiles will not change shape at the same mach values therefore the scaling will be off and drag predicted incorrectly. Sometimes over and sometimes under predicted. Hope that makes some sense.
--- aim small miss small ---
--- aim small miss small ---
take that out to waterman, get it on at 600 by walking it back from 300 or whatever it takes
once you are happy with the 600 zero, take it down to the 25 yd range, making no adjustment - with the turret at the landscape timber shoot a couple then measure point of aim vs point of impact
- use the .243 G7 for the 175 SMK - adjust the MV on the ballistic program until you match the real world drop results between 25 and 600 yds (it will be right about 11.2 moa)
this will give a good enough results to get you on paper to 1000
once you are happy with the 600 zero, take it down to the 25 yd range, making no adjustment - with the turret at the landscape timber shoot a couple then measure point of aim vs point of impact
- use the .243 G7 for the 175 SMK - adjust the MV on the ballistic program until you match the real world drop results between 25 and 600 yds (it will be right about 11.2 moa)
this will give a good enough results to get you on paper to 1000
all I got to say about this, am I going to buy what some interweb blowhards say about this or a published ballistics engineer employed by a top bullet manufacturer/innovator
----easy choice -----------
Interesting thoughts, Internet Blowhards...
What about other ballisticans, like Gerald Perry before he passed, or the Fact Field Firing Solution doesn't even use G7, at all, and is accurate to distance.
There are guys outside the country, Ballisticans who have ran the numbers alongside Doppler, and they are indistingiushable from each other.
There are lot more than just internet blowhards who realize it is one model, and one that has was left unused since the 50s,
Seriously it requires the same exact amount of effort, the tweaks might be smaller overall, but they are still necessary as the average provided does not fit every situation, the exact same as G1.
It's not blowhards as much as shooters with real world experience who know how to separate the hype from the reality of the situation.
You can model it several ways, sure if your particular model weights G7 more than it does G1, you have an argument but not all ballistic models do this.
What about other ballisticans, like Gerald Perry before he passed, or the Fact Field Firing Solution doesn't even use G7, at all, and is accurate to distance.
There are guys outside the country, Ballisticans who have ran the numbers alongside Doppler, and they are indistingiushable from each other.
There are lot more than just internet blowhards who realize it is one model, and one that has was left unused since the 50s,
Seriously it requires the same exact amount of effort, the tweaks might be smaller overall, but they are still necessary as the average provided does not fit every situation, the exact same as G1.
It's not blowhards as much as shooters with real world experience who know how to separate the hype from the reality of the situation.
You can model it several ways, sure if your particular model weights G7 more than it does G1, you have an argument but not all ballistic models do this.
We seem to have a problem of definitions. When someone asks "is G1 better than G7 for such and such bullet?" I assume that they mean one bc and using standard drag functions- plug it in and go. In that case, there is always a right answer. They are not the same, and one choice will be better. For most long range bullets, the answer is G7. For some bullets it matters more than others. For all it is a small difference that does not even approach significance until you hit very long ranges. This is what Bryan Litz wrote his book about, for those reading in between the lines. But in the purest (dare I say, academic) sense, in no way is a G1 the same as a G7. It is not a mils vs MOA type situation. You do not get the same answers, and therefore one MUST be better than the other.
That said, some people seem to have a wider interpretation of what "G1" means, which is all fine and good as long as it's understood. Using three or four velocity-dependent BC's and matching up against a G1 drag function can provide better results than a single G7 BC. But are you really using a G1 drag function anymore? No. You're using a custom drag function that was derived from a G1. Same thing with Pejsa and its derivatives. Starting with a G1 drag function and then modifying it means you are not using G1 drag function. You're using a modified G1 drag function.
This is the point in the conversation where some pragmatist gets fed up and says "who cares, just shoot and write it down". And that's a great point. If all you are after is results, then you do not need a computer or a drag function or any of this. You just need some time at the range and you will get a drop table that is as accurate as we can measure. But at the cost of understanding. If you want to understand, then you'll want to look under the covers, and figuring out G1 vs G7 is a great way to get your hands dirty.
That said, some people seem to have a wider interpretation of what "G1" means, which is all fine and good as long as it's understood. Using three or four velocity-dependent BC's and matching up against a G1 drag function can provide better results than a single G7 BC. But are you really using a G1 drag function anymore? No. You're using a custom drag function that was derived from a G1. Same thing with Pejsa and its derivatives. Starting with a G1 drag function and then modifying it means you are not using G1 drag function. You're using a modified G1 drag function.
This is the point in the conversation where some pragmatist gets fed up and says "who cares, just shoot and write it down". And that's a great point. If all you are after is results, then you do not need a computer or a drag function or any of this. You just need some time at the range and you will get a drop table that is as accurate as we can measure. But at the cost of understanding. If you want to understand, then you'll want to look under the covers, and figuring out G1 vs G7 is a great way to get your hands dirty.
The benefit is explained at and beyond transonic, at supersonic ranges it's insignificant, the point that was being made was transonic and beyond.
Ask yourself how important is that ? If your working on the outside edges ok, but most people are concerned with their shots that are within supersonic ranges.
G1 was the law of the land for more than 50 years, you can say it's always been modified but who cares, the end user is not writing software or a ballistic curve. The END RESULT is the point... Period. If you want to go to a software developer site and argue the merit of the pure model, great, by all means. But we are concerned with hits in paper. If JBM will give you a stepped or banded G1 for the same price as your single G7 and it's better, guess which is more accurate?
I will tell you now, it won't be long before you see stepped or banded G7 and the Applied Ballistics Kestrel is already offering and using a custom curve. If it's so good, so much better why is that ?
Ask yourself how important is that ? If your working on the outside edges ok, but most people are concerned with their shots that are within supersonic ranges.
G1 was the law of the land for more than 50 years, you can say it's always been modified but who cares, the end user is not writing software or a ballistic curve. The END RESULT is the point... Period. If you want to go to a software developer site and argue the merit of the pure model, great, by all means. But we are concerned with hits in paper. If JBM will give you a stepped or banded G1 for the same price as your single G7 and it's better, guess which is more accurate?
I will tell you now, it won't be long before you see stepped or banded G7 and the Applied Ballistics Kestrel is already offering and using a custom curve. If it's so good, so much better why is that ?
What would really be useful is Cd/mach curves for some of the actual long range bullets out there today. Much thanks to Litz for the testing he published which gave us the next best thing.
Good replies on the differences, I wasn't even considering the accuracy of the custom G1 curves in my original reply. True those can be as good or better than straight up G7. In the end, the errors between drag models are likely less than my trigger pull error anyways but its fun to learn the science behind it all so when it comes time to pull the trigger, you've only got yourself and Murphy to blame when you miss.
--- aim small miss small ---
Good replies on the differences, I wasn't even considering the accuracy of the custom G1 curves in my original reply. True those can be as good or better than straight up G7. In the end, the errors between drag models are likely less than my trigger pull error anyways but its fun to learn the science behind it all so when it comes time to pull the trigger, you've only got yourself and Murphy to blame when you miss.
--- aim small miss small ---
Last edited:
Do you honestly think I shoot flat base bullets at matches? I have been using G1s with JBM ballistics for years and they hit. That's with HPBT/AMAX bullets.
To paraphrase Lowlight, don't believe the hype.
You might be surprised at the results some 1000 bencresters have gotten with flat based bullets. They have their advantages. Ballistics, of course, isn't one of them.
Yes I agree, don't believe internet hype. Check out the facts for yourself, here are the sources I've learned from:
www.appliedballisticsllc.com/articles.htm
Book: Applied Ballistics for long range shooters -Litz
Book: Modern Exterior Ballistics -McCoy
And many more but those are the top 3 for trajectory analysis.
--- aim small miss small ---
More power to ya. The tried and true method for gathering data.
For those interested in the science like I am, I re-found a great summary of the G1/G7 topic from Berger:
http://www.bergerbullets.com/a-better-ballistic-coefficient/
External ballistics - Wikipedia, the free encyclopedia
Half way down the page is a comparison of G1, G7, Pejsa and Doppler for a Lapua VLD. Judge for yourself.
I can accept "It's not an important distinction", or "Neither G1 nor G7 will be perfect". But what I can't accept is "G1 is better than G7 for long-range boat tails" because it's simply not true and has been well documented with test data from multiple sources.
Half way down the page is a comparison of G1, G7, Pejsa and Doppler for a Lapua VLD. Judge for yourself.
I can accept "It's not an important distinction", or "Neither G1 nor G7 will be perfect". But what I can't accept is "G1 is better than G7 for long-range boat tails" because it's simply not true and has been well documented with test data from multiple sources.
Did I say better? No. It's just as accurate though. I have tried both and just kept using the trusty old G1.
Woostri if you are interested in science and just want to look at all the numbers then all the power to you as well but don't try and tell me that G1 doesn't work because I know from shooting it that it does.
Woostri if you are interested in science and just want to look at all the numbers then all the power to you as well but don't try and tell me that G1 doesn't work because I know from shooting it that it does.
Next weekend I'm going to shoot at 600yds and 25yds, (Thanks George!) and report if G1 or G7 was closer. I understand that neither will be perfect, but being a 24/7 gun-geek guy my whole life, I need something to wrap my mind around when I'm not actually shooting! Can you say obsessed? Lol
Hm. I dont recall ever telling you that G1 doesn't work. Only that the drag profile shape of the G7 would be closer to that of your HPBT bullet therefor will give you a better prediction of drop. But I also stated that the differences in drop are minor and likely to be masked by other errors in real world shooting therefor either can be used as long as the input number was accurately obtained. I would agree that in any real world testing, it would be difficult to prove one's worth over the other. The larger differences would show up in the transonic realm (as Lowlight mentioned) but most long range shooting is still well into the supersonic realm.
This I can also accept. The qualifier is an important one.
I can completely relate to geeking out about guns... Hence why I asked for the McCoy ballsitics book for Christmas one year.
It will be interesting to see the results of this test. I've not used the Iphone ballsitic AE program, but you mentioned it has the Litz published BC's with it? I use "Shooter" for android. All the apps should report the same results given the same inputs as they are all modified 3DOF with the same equations of motion.
Run the numbers at 600 and you'll find that the predicted difference is pretty damn small. Other factors dominate at that range. Even at 1000, you'll need some very good measurements for your inputs (velocity, wind, BC, atmospherics, angle of fire, etc.) and a very accurate rifle to definitively tell the difference.
Bold portion, in theory, yes. In reality, no.
The difference is so small and not due to the G7 being more accurate but in the whole dependent on how both are run. You will get more variance from your scope tracking. The problem is people come in here and say the G7 is better for HPBT bullets and then people searching see that and start to repeat it and then it keeps rolling and becomes "truth". When in reality it's not.
I have compared them and the G1 shows my bullet will impact about 2.5" higher (@ 600yds.) than the G7 states. I'll be able to determine which is more accurate. I wish I could shoot it now, but the Bear's game and tornados in the area are kinda preventing that! Lol
Up till now I've been giving you the benefit of the doubt that you actually knew what a BC was and how its calculated. Alas I can't believe that anymore. I've not doubt you are an experienced shooter and could likely outshoot me but have you ever actually considered reading anything about it? I seriously recommend this link I posted earlier:
http://www.bergerbullets.com/a-better-ballistic-coefficient/
Its written by Brian Litz, I don't think anyone can argue the validity of his knowledge AND experience.
The ballistic ap I'm using has the Litz listings, so I do have the correct Litz BC.
No, it really is true. Bryan Litz has data for hundreds of bullets published in his book verifying that. The only ones for which the G1 is better are the Barnes hunting bullets and other like that. Every other bullet tested is a better match for a G7. I posted another link in this very thread that shows that for the Lapua VLD, it is true. There is an article floating around somewhere by a Sierra ballistician that says it's true. The Sierra loading manual explains the reason they publish velocity dependent BC's - it's because G1 is not a good match for some bullets - long range boat tails. Heck, look at the shape of the standard projectiles. Which one looks like the bullets you shoot? My bullets look an awful lot like the G7 projectile and don't look much at all like the G1 projectile.
[MENTION=13650]Graham[/MENTION] you hear that? Your data is wrong using the G1 because the G1 isn't a good match to the bullets we use. Says it in a book.
I own the Litz book. I know the science. I also know my experience. I use my real world experience and the G1. You can use what you like.
I own the Litz book. I know the science. I also know my experience. I use my real world experience and the G1. You can use what you like.
Graham just said he's using multiple BC's. That means implicitly that the G1 is wrong. He's just found a way to compensate for that.
Make my day! This is better than a Bears game. BB
So you are saying the G7 BC is constant across the whole velocity range used? No variances at all?
In nuclear physics, you look at data next to your model and figure out which works best for which situations. I assume its the same here, find the model that most accuratly describes your bullet. If you can't afford doppler radar, you can spend some time doping your rifle/bullet combo. In this case there isn't a best model, but there will usually be a better model for your specific bullet. In some cases, the actual value will lie directly between the two models.
Of course not. I'm saying it will very less (sometimes a lot less) than a G1 BC. When using a single BC, the G7 will provide better results. There is no cost whatsoever to using a G7 BC. I don't understand the resistance.
M
milo 2.0
Guest
I think after all this, and previous ones, pride is at stake!
Glad you said that but again your statement that when using the single number the G7 will be better is not my experience. I have no problem using a G7 if it worked better but it doesn't in my use. I have tried it.
I don't have access to 1000 yard ranges to get data for matches so I run all my data on JBM and go to matches. It works. Very well actually. When someone tells me it doesn't because a book says it then I have to disagree.
Not at all. See above. I always try new things and if something works better then I use it. I am very open to new advances that make my job easier.
Similar threads
