With the development of smaller high BC projectiles- are larger magnums obsolete for ELR shooting?

[6ShotsOr5?]

I just ran a couple of cases in Ballistic AE using conditions similar to Whittington Center around 6500 ft elevation. I used a 15 mph crosswind and I turned off the spin drift and coriolis, to just consider wind only. A 0.264” Berger 140 VLD at 2850 MV from an 8 twist barrel had 367” wind drift at 2000 yds, and was at 1050 fps terminal velocity. The .338 Berger 300 gr Hybrid at 2700 MV from a 9.3 twist barrel had 254” wind drift at 2000 yds and was still at 1286 fps downrange. Advantage — heavy bullet. I have a couple of .264 caliber Rifles and a .338LM and I would use the .338 for 2k yds. The wind drift difference is magnified closer to sea level.

 

[steve123]

One other thing to consider is detecting where your bullet went. At extreme distances it's much easier to see hits in the dirt with a heavy bullet as well as hearing the sound on steel or seeing marks on steel. These are the problems I had when I shot my 6.5 saum at a mile and that's with 140 hybrids at 3175 fps.

Before I had my 6.5 Saum I had a chance to compare my 375CT - 350's at 3200 fps and my 30-375R - 240's at 2900 fps. It was comparatively easier to detect where the bullet went with the 375CT and wind drift was around half as much.

Just an FYI, the 30 was more accurate than the 375CT, it didn't matter much because when is it ever calm out?! The 375 was easier to hit with at extreme distances.

 

[dcali]

If they have the same or similar BC, the force of the air would be the same. A 185gr bullet would have more momentum and would retain velocity better. It would slow down at a lesser rate than the 140gr bullet, assuming, as you said, they have the same or very similar BC.


The 185gr bullet would drop faster though.

You've left out velocity. If the BC *and* velocity are the same, the trajectory will be the same. That extra weight is already rolled into the BC for the heavier bullet, so if they have the same BC, that means that the heavier one is either blunter (is that a word?), or a higher caliber.

The thing that trips people up is that velocity is typically not the same - we usually trade velocity for weight when selecting a bullet (because our rifle is already built).

 

[dcali]

Come to Montana in August, bring your 6.5 and shoot the E2K match (at 2000 yds.) - Show us how well you can shoot that 6.5

I said "get you there", not win!

 

[LA50SHOOTER]

I said "get you there", not win!

.223 Remington can also "get you there" - That doesn't mean that we'd shoot it.
I'm NOT here to "kick dirt" about the 6.5 caliber. - It's not my "cup of coffee" and I'll leave it at that, as long as I'm not hearing unreasonable "dreams" about it. - Nothing Personal -

Kind Regards - Ron -

 

[243Mendoza]

BergerFan- I believe BC is highest at the muzzle and then drops as the speed drops. The larger heavier bullets are better when it comes to energy on target just because of the sheer weight. I don't think anyone is doubting that. I think Doc. is saying that if two bullets have different weights/cal. but have the same speed and same BC then in theory they should cut the wind the same and fly the same. That is my understanding also.

Energy is a function of mass and speed squared. If you double the mass, you double the energy but if you double speed, energy will be quadrupled. So energy is more sensitive to speed than mass.

 

[micmac]

Why the notion that smaller high BC projectiles are progresing any faster or more than larger caliber projectiles. In all aspects odds are stacked against smaller projectiles. Only thing that is happening is that ranges calibers are usefull are extending but is happening on the large caliber front even more as solids are far more viable , in sub 30cal solids have hard time geting any substanital gains

 

[dcali]

.223 Remington can also "get you there" - That doesn't mean that we'd shoot it.
I'm NOT here to "kick dirt" about the 6.5 caliber. - It's not my "cup of coffee" and I'll leave it at that, as long as I'm not hearing unreasonable "dreams" about it. - Nothing Personal -

Kind Regards - Ron -

I do think you could have some fun with a 6.5-284 and some turned solids. But I agree, at 2000, there are better choices.

 

[retired]

there may be
i am bringing a larger vane flag.
the intent is to make a "range" flag out of it.
it can go about 12' above line of sight.
it is easy to see at 800.
we will have to try it out and see what management says.
either right or left of range, or dead center if there is a safe spot.

Wind flags will not be allowed ABOVE the line of fire for this event & there doesn't appear to be to much in the way of tree's & stuff to check either. - A 338 cal. bullet @ 2940 will have a peak trajectory of approx 68 feet @ the 1300 yard point. - I'm betting that 6.5 will need 85 to 90 moa of up from a 100 yd. zero to get to the 2000 yard line.

 

[retired]

get donovan to run your numbers. and see what he says peak is for a 2000 zero, base on a 100 yd zero.
i get 45 feet with a 230 308 at 2800 at 4000 ft. 75 moa up from 100 zero

Wind flags will not be allowed ABOVE the line of fire for this event & there doesn't appear to be to much in the way of tree's & stuff to check either. - A 338 cal. bullet @ 2940 will have a peak trajectory of approx 68 feet @ the 1300 yard point. - I'm betting that 6.5 will need 85 to 90 moa of up from a 100 yd. zero to get to the 2000 yard line.

 

[Steve Donlon]

I have to quote German Salazar " Muzzle Velocity is a Depreciating Asset, Not Unlike a New Car, But B.C. , Like Diamonds, is Forever". I will go with heavy bullets, they will always be better if you can handle the recoil. In most cases most people can not. But if you can my respect goes out to those who can.

 

[Eric Leonard]

I was always taught that a .300 G7 was a .300 G7 and the weight didnt play a role in anything except energy delivered on target,,,

 

[dkhunt14]

I was always taught that a .300 G7 was a .300 G7 and the weight didnt play a role in anything except energy delivered on target,,,

I thought sectional density comes into to play some how. I also thought the farther out you get the better a bigger bullet is. Matt

 

[dcali]

I was always taught that a .300 G7 was a .300 G7 and the weight didnt play a role in anything except energy delivered on target,,,

That's correct. BC already accounts for weight.

 

[Alex Wheeler]

The heaviest for caliber bullets dont seem to be the most accurate bullets. Look at competition and usually the choice of bullet is one step back from the highest bc options.
I have wondered how we can use one number (bc) to predict front drag (drop) and side drag (wind). I feel like there has to be some "estimating" going on.

 

[Ballisticboy]

The heaviest for caliber bullets dont seem to be the most accurate bullets. Look at competition and usually the choice of bullet is one step back from the highest bc options.
I have wondered how we can use one number (bc) to predict front drag (drop) and side drag (wind). I feel like there has to be some "estimating" going on.

The usual method of producing a high weight bullet through increasing the length of the bullet introduces many problems with achieving satisfactory gyroscopic and dynamic stability. Increased twist rates are required for gyroscopic stability but this then increases dynamic instability which in turn leads to reduced precision and larger group sizes. Therefore the heaviest bullets for calibre, while having an improved cross wind response for a given muzzle velocity, will not necessarily give the best results due to other factors.
A cross wind does not blow on the side of a bullet unless you have a grossly gyroscopically overstable bullet. The bullet, when flying in a cross wind, does not see the air coming from two different directions, it only sees one airflow coming from the combined direction from the bullet forward speed and the cross wind. By definition a stable bullet will turn to face the combined airflow direction and thus there is no airflow from the side of the bullet. It does mean however that the bullet drag is acting in a direction at a small angle to the line of flight and it is this force which is producing the down wind drift not the air blowing on the side of the bullet.
For a full explanation with diagrams you can look at this post on an airgun forum (https://www.airgunforum.co.uk/community/index.php?threads/understanding-wind.228773/#post-1655061). It is for airgun pellets but it is the same for all gun launched projectiles.

 

[dcali]

The heaviest for caliber bullets dont seem to be the most accurate bullets. Look at competition and usually the choice of bullet is one step back from the highest bc options.

People seem to have a better understanding of BC and wind than they do of twist rates and their impact on precision, so they tend to overdo BC as if there isn’t a trade off. In TR, everyone wanted (myself included) to try 215s. And we found out that they’re not magic. So now people are jumping in with 200s. I’m thinking we may settle in at a well done 190-195. Balance is the key.

 

[Ned Ludd]

People seem to have a better understanding of BC and wind than they do of twist rates and their impact on precision, so they tend to overdo BC as if there isn’t a trade off. In TR, everyone wanted (myself included) to try 215s. And we found out that they’re not magic. So now people are jumping in with 200s. I’m thinking we may settle in at a well done 190-195. Balance is the key.

Given the outstanding results that have been achieved in other disciplines and by a few in F-TR using the 215s, it is highly likely that the common "trade off" is most F-TR shooters' inability to effectively manage the 215's recoil in an 18 lb rifle, rather than any inherent design issue with the BC or bullet itself. If you can't manage the recoil effectively and lose a lot of points to vertical, high BC values have relatively little importance.

 

[dcali]

Recoil is a big one, it's a little bit the bullet as well. A large part of dispersion is proportional to twist rate, and longer bullets are more sensitive than shorter bullets. I think this is in large part why people consider the juggernaut to be so easy to work with (it's pretty short for its weight), and possibly why secant ogives have a reputation for being finicky (they're longer for their weight).

 

[270WinDude]

You've left out velocity. If the BC *and* velocity are the same, the trajectory will be the same. That extra weight is already rolled into the BC for the heavier bullet, so if they have the same BC, that means that the heavier one is either blunter (is that a word?), or a higher caliber.

The thing that trips people up is that velocity is typically not the same - we usually trade velocity for weight when selecting a bullet (because our rifle is already built).

I think that's a hard thig to wrap ones head around I've noticed. It's easier to look at a BC and compare bullets but it's harder to gauge the amount of velocity that could be used to compensate for lower BC and what distance that threshold would be. Some sort of ratio would be nice. Also an earlier point you made struck a chord with me also. In my peer group of novices, I've noticed people have a hard time making cartridge comparisons regarding average bullet weights for various cartridges commonly used per caliber. To OP question... as an outsider who literally just learned what BC stands for a couple months ago, it appears to me that the "smaller" .224 (think 90gr vld), .243, and .264's are getting new life breathed into them that wasn't there before. When I read old threads it seems like past 10 years has had a minor revolution in bullet manufacturing and the implications on consumer choice are slowly adapting to it. Time will tell, but look at what millennials are doing...