# Do you have a good enough eye



## Plainsman (Jul 30, 2003)

I want to do a little experiment here. Mostly because I am having some trouble believing some of the data companies provide. I'll tell you what I am looking for after a few posts.
What I want you to do is look at these two bullets and tell me which one you think has the highest ballistic coefficient. Both are 30 caliber. One is 165 gr and the other is 168 gr. Tell me if you think the one on the left has the highest ballistic coefficient or the one on the right. Also, why did you come to the conclusion you did?
Sorry, it looks like the camera focused on the background, but I hope you can see the bullets good enough to make some ballistic coefficient judgements.


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## Sasha and Abby (May 11, 2004)

my vote is the one on the left... more surface area...


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## huntin1 (Nov 14, 2003)

I am going to say the one on the right. The ogive is more streamlined as is the boattail, both should contribute to a higher BC when all else is equal.

Just a guess, I could be wrong. It has happened once or twice. 

huntin1


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## xdeano (Jan 14, 2005)

I too would have to go with the one on the right, just because of the secant ogive, and bearing surface. The boat tail is also at a steeper angle and longer, which might add to less friction.

The one looks like a 155g Lapua with the secant ogive and the other looks like a 175g SMK because of the tangent ogive.

I think huntin1 and I are going to be wrong for some reason. Why would you put it up if it makes sense? That being said the left is probably the right one. Dang trick questions.

xdeano


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## D_Hage (Nov 10, 2004)

I was thinking the right for the same reasons as posted above, but have the same feeling that I am wrong as well.


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## Swifty56 (Sep 14, 2009)

I would have to agree with the one on the right, however my reasoning is that since one is a 168 gr, and the other a 165 gr. The one on the left looks like a moly or otherwise coated spire point boat tail, whereas the one on the right looks alot like a 168 gr FMJ Palma or military match design. Just my guess  
Also must agree it is kind of a trick question seeings how the B.C. changes with an increase or decrease in velocity. To my understanding anyway.

Swifty


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## Plainsman (Jul 30, 2003)

Well here is the deal. 
The bullet on the left is a Nosler Ballistic Tip (165 gr). I run a program for my 300 Win Mag and it hits low out at 800 yards. I run the load across my chronograph, but lowered it to look at actual shooting performance. That got me on at 800, but high at closer yardages. Next I lowered the ballistic coefficient of the bullet and perfect. Everything fits if I lower the ballistic coefficient from the advertised .475 to .445. 
The bullet on the left is a Berger VLD (168 gr.). These bullets are very streamline yet they advertise only .473 ballistic coefficient. I doesn't make sense to me so I am loading some in my 308 and checking the difference at 800 yards.

I have another problem. My old loads in my 300 Mag gave me 3350 fps with R22. This year I am getting 3230 with the same powder and weight. I bought another scale to double check my powder weight. The load is correct which leaves me wondering if the powder has changed. I tried powder from two different lot numbers with the same results.

Something else interesting. I just tried R25. I don't know what the accuracy is like yet, but I got the Berger 185 gr VLD to 3250 fps. The primers looked good, but the extraction felt a little sticky so I backed off to 3200 fps. At that velocity it appears I am striking a foot higher at 800 yards. At 1200 yards my energy went from 500+ foot pounds to 917 foot pounds. The ballistic coefficient is .549 and these are the new Berger hunting bullets. I am anxious to check accuracy.

Like you guys I think in reality the bullet on the right has a higher ballistic coefficient. I hope to find out some time within the next week.


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## bearhunter (Jan 30, 2009)

is there a difference between secant and tangent ogive oke: good god i got dizzy reading this :-?


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## xdeano (Jan 14, 2005)

LOL. there sure is, not much but there is. It looks cooler too. 8)

Plainsman,
The drop in velocity has me to believe that ambient air temp or cartridge temp would be messing with your pressures, causing more or less velocity.

The best bet would be to get two identical chronographs and measure your velocity at 10ft and at 100yds. This will give you your actual BC of the bullet. I don't know if i'd fully trust some of the manufactures with their BC. Hay we'll just give it a good bc and people will buy it... I'd probably go with the Bc that you came up with on the 165's. If you need another chronograph I need an excuse to get down there and to take some time off.

Let me know how those Berger 168's work. I'd like to know. I might be fun to mess with. I'd also like to mess with some of the 175's.

xdeano


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## Plainsman (Jul 30, 2003)

xdeano, I thought about the temp thing but I checked the 165 just before the ND elk season and it was in the 90's. Last week when I went out I took them from the loading room and put them under my down vest. I took one at a time out to shoot and between shots took the rifle back into the truck to warm up. I was getting 3190 to 3220 fps out of the 185 gr VLD's out of my 300 Win Mag. I figured if they were hot loads in the cold I would blow myself up next summer.


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## barebackjack (Sep 5, 2006)

The bullet on the left looks to have a substantially longer OAL. Wouldnt this somewhat cancel out the steeper ogive of the bullet on the right, in effect making them somewhat more equal (in reference to BC)?

I always thought a secant ogive was to improve the BC of shorter (lighter) bullets and put them on a level playing field with the tangent ogived, longer (heavier) bullets?


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## xdeano (Jan 14, 2005)

i believe you're right on both accounts.

I've heard a lot of good things about the berger hunting bullets, I've shot coyotes with the 90g match bergers in 243 and they are nasty little pills, and a lot more consistent shot to shot than a Scenar, even though I haven't shot the scenars in 243, just the 308. I wonder what the difference is between the hunting bullets and the target bullets that Berger is making anyhow, they have the same J4 jacket.

xdeano


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## Plainsman (Jul 30, 2003)

barebackjack said:


> The bullet on the left looks to have a substantially longer OAL. Wouldnt this somewhat cancel out the steeper ogive of the bullet on the right, in effect making them somewhat more equal (in reference to BC)?
> 
> I always thought a secant ogive was to improve the BC of shorter (lighter) bullets and put them on a level playing field with the tangent ogived, longer (heavier) bullets?


I'm not sure how that would work out. I have shot a lot of X bullets, but I don't believe their ballistic coefficient. They are copper not lead so the 30 caliber 180 gr that I shot were the same length as the 200 gr Nosler Partitions that I shot. I think ballistic coefficient of a lighter material is misleading because the high ballistic coefficient of the X bullet and the lower ballistic coefficient of another bullet I was shooting hit at the same elevation out to 1000 yards.
I think the lighter Ballistic Tip is longer, but some of that length is plastic and air space interior along the Ballistic Tip shank.


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## Jiffy. (Dec 3, 2009)

Looks can be deceiving, as can ballistics calculations.

Such is why one needs to test in real life, to ensure generated data and real life data jive.

I've been shooting Sierra's 155 Palmas out of my 308 for a while now and they look FAR from streamlined. In fact they have been dubbed "fat chicks" by certain shooting partners. In actuality they are .504 and I can say for certain that is what they really are. Over 1500 in the test group from 0-1K, I keep copious notes...I'm a nerd like that.


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## duckmander (Aug 25, 2008)

I am not even close to an expert on this. You could prolly take what I know about this write it on the point of a very sharp pencil. and still have enough room to write the lords prayer right beside it.
so heres my shot at it.

But I believe the one on the left is heavier. and it also has a soft point. 
which should be more evergy efficiant.

Meaning it should hit harder expand more and do more dammage.

Just my .02


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## farmerj (Jun 19, 2004)

I think temp and humidty are playing more into this than is being allowed for. More so Temp than humidty, but with the recent temps...It's possible humidty will possibly have that "little edge" on the BC.



> To summarize we have seen that changes in air density can have a somewhat significant change on the equivalent ballistic coefficient in extreme cases. A change in altitude will have the greatest influence followed by changes in temperature. Fluctuations in the humidity level will also change the air density and ballistic coefficient, but the amount is at most about one percent. Because humidity has such a small effect it can be ignored.
> 
> Increasing the temperature or altitude will increase the ballistic coefficient. Increasing the barometric pressure decreases the ballistic coefficient. It has the same effect as going down in elevation. Remember an inch of pressure is equivalent to 1000 feet of altitude.


While you can simulate the temp of summer putting it inside your jacket, you're still going to be well over a 20 degree temp change compared to a summer day.

Humidity- Oye, no way I can think of to simulate that in this part of the country.

http://www.riflebarrels.com/articles/bu ... midity.htm



> To see the effects of a humidity change, if the humidity level was actually 75% in Phoenix and the temperature stayed at 95 degrees, the ballistic coefficient would be .304. That is not a significant change, about 1%, but it is interesting to note that the ballistic coefficient increased with the more humid air.
> 
> Probably the most humid and hot conditions I have shot in were during the 1987 Nationals at Charlotte, North Carolina. The temperature was about 100 degrees and the humidity level not far behind, probably 90%. Charlotte has an elevation of about 750 feet. For these conditions the ballistic coefficient of that typical benchrest bullet would be .300, about the same as Phoenix. If we dropped the temperature in our simulation to 30 degrees at Charlotte and kept the humidity at 90%, the ballistic coefficient would be .256. This is a much more significant change, about 15%.
> 
> The range in Helena, Montana is just east of the continental divide at an elevation of about 5300 feet, just over a mile high. At a temperature of 70 degrees and humidity level of 25% the ballistic coefficient would be .330. That value is quite an increase over our sea level figure of .265, about a 25% improvement.


More information here.
http://www.exteriorballistics.com/ebexp ... 4th/51.cfm


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## Plainsman (Jul 30, 2003)

> While you can simulate the temp of summer putting it inside your jacket, you're still going to be well over a 20 degree temp change compared to a summer day.


Tomorrow I will have a hand warmer in the same pocket along with a digital corded thermometer. The other day I only had a thermometer and that was at 75 Degrees. Seeing that body temp is 98.6 it was cooler, but not all summer days are 90 degrees.

However, I am talking about the manufacture advertised ballistic coefficient and shooting them side by side on the same days including warm days and cold days. The difference in ballistic coefficient with bullets that weigh the same, and go over the chronograph at the same speed, is evident when shooting at 800 yards and 1000 yards when one strikes a foot higher than the other.


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## farmerj (Jun 19, 2004)

I am thinking that keeping the round at temp will only have an effect on the burn of the powder.

The actual bullet will be effected by the temp and humidity of the air. That's not something that you can actually put in your pocket to test.

A good example of why having a good logbook is essential to the minor nuances of shooting between summer and winter or even week to week.

The actual air temp and lack of humidity in the winter can't be changed. Course this could be a good excuse to take a trip and go down south.


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## Plainsman (Jul 30, 2003)

I don't think temp alone will change anything. Barometric pressure will have the same affect as elevation though. A high pressure system will have more dense air than a low pressure system. Also, humidity can slightly change air density. It's like hammering a nail into pine vs hammering a nail into oak. 
I think we see changes in point of impact with long range shooting with temperature changes, but fail to realize the temperature changed with a weather front and it was barometric pressure changing our impact point not the associated temperatures that came with it. Of course if weather systems are stable and temperature rises hot air has less density. If it wasn't lighter hot air ballons would not work. Again though it's air density and not temperature. 
I think I would check the barometric pressure on my Garmin before I was concerned about the thermometer.


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## Jiffy. (Dec 3, 2009)

Plainsman said:


> The bullet on the left is a Berger VLD (168 gr.). These bullets are very streamline yet they advertise only .473 ballistic coefficient. I doesn't make sense to me so I am loading some in my 308 and checking the difference at 800 yards.


Where did you get your data? I've got the .308 168 gr. Berger VLD at .512

Also I would assume you mean the bullet on the right. The bullet on the left is the bullet you were previously talking about. Not only that but although my eyes aren't as good as they used to be, I can tell for certain the one on the left is not a Berger VLD...

:wink:

Air density absolutely positively make a difference. One has to just have a basic knowledge of physics to understand that. I think what perplexes a lot of shooters are the amount of varibles involved. Many, as already stated, can be ignored as they are miniscule at best. However, you start adding them up and they will of course alter POI. At further distances this just magnifies.

AND of course you have the human varible....but we all know that one can ALWAYS be factored out.


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## Plainsman (Jul 30, 2003)

Left, right, left, right, things get confusing in my old age. 

Your right, errrr maybe left.  Anyway, your correct. The bullet on the left is a Nosler Ballistic Tip (165 gr) that I moly coated. The bullet on the right is the Berger VLD that I moly coated.

Air density became very apparent to me when I started running programs for elk hunting in the mountains. If you go from 1350 ft here in Jamestown to 9000 ft in Colorado you can add a few hundred pounds of energy at 500 yards. That, and you are going to hit about six or eight inches higher. Somwhere in that ballpark, I don't have the data at hand.

Maybe the difference in the ballistic coefficient that you have and the one that I have is because I have the Berger VLD Hunting, and not the match. Maybe like some companies they exaggerated in the past and corrected their new data. This box was purchased last week.


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## Jiffy. (Dec 3, 2009)

HAHA!! We could just use port and starboard, that would really mess things up.

Ok, yeah I'm not sure the difference in BC between the two, I'd have to look it up. That could very well be it if you have the hunting VLDs. Do the hunting VLDs like to jump better than the match? I have not tried the newer hunting VLD. Besides they are too expensive, I'd go broke shooting them.

What companies have you noticed exaggerated BCs? The box I have is a couple years old, the old yellow box.


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## Plainsman (Jul 30, 2003)

As to expense, they are not any worse than Ballistic Tip now. I think in the local stores Ballistic Tip are $22 for 50, and the Berger I paid $45 for 100 for at Scheels.
Bullet cost is why I bought a bunch of casting equipment this year. Mostly for my 45/70 and 44 mag, but I intend to get more moulds. I have 357 moulds also, but am thinking about getting a 30 caliber. I have a friend that shoots a 150 gr at 2200 fps with good accuracy. That's from a 308.


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## Jiffy. (Dec 3, 2009)

I pay 136 per 500 for the 155 Palmas. I've got them going around 3000ish for my heavy load (pretty much ragged edge) and 2920 for my light F-Class load (308). I've had very good results with them.

I'll probably get into casting if I end up shooting IDPA like I hope to.


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## farmerj (Jun 19, 2004)

I didn't do much with LR shooting last year at all. So pulling the cob webs off of my "recollection". So right now, google is a good friend.

My thinking with your difference between summer and winter shooting.

Been search for the relationship between temp change and drop. I couldn't remember it for sure. Here is some of the info I found.


> At 300 yards there is 1 MOA change in elevation per 20 degree change in temperature.
> At 600 yards there is 1 MOA change in elevation per 15 degree change in temperature.
> At 1000 yards there is 1 MOA change in elevation per 10 degree change in temperature


This isn't exactly as I remember it, but it's a very good start. I just wish I knew where all my notes and logbooks were. Memory tells me the difference was 1 MOA per 20 degree change in temp at 100 yards. At 1000 yards, that would give you a bunch of drop / rise depending on which way you went. Temp having a huge impact on air density. Look at a balloon. How big is a balloon at room temp? How big is the same balloon if you put it outside when it's 0 degree's? 32 degrees? Same mass of air, just a lot smaller volumn.

Basically, Temp and altitude were our biggest enemies. Temp having the biggest impact. I have always worked on developing loads in the summer and not in the winter. The biggest issue as you stated. To avoid over-pressure situations.

Software is a good way to get close to where the POI/ POA should be...

But nothing beats a good logbook and actual results. Damn, I wish I could find mine.


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## Jiffy. (Dec 3, 2009)

farmerj said:


> But nothing beats a good logbook and actual results. Damn, I wish I could find mine.


You LOST your logbook?!?!

Go find a pole and give me 50!!!!


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## farmerj (Jun 19, 2004)

lost by divorce... I wasn't allowed to get my belongings out of the house. She gave me what she wanted. :eyeroll:


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## Jiffy. (Dec 3, 2009)

OH man that's rough!!


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## farmerj (Jun 19, 2004)

all though "records" I had.... eace:

I get to go through ALL that shooting to rebuild the data again.....


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