Have we maxed out BC?

[Sling]

Seems like BC for each caliber is about as high as it can be. There might be room for a little improvement but very little. It takes mass to create very high BC. I doubt we will ever see a 6mm bullet with BC over .600 just because there is not enough mass. When Bryan Litz came out with the "Hybrid", it increased BC some. If we ever get to that point, looks like gain twist barrels might be the answer. Bartlein is making gain twist .375 barrels for very heavy for caliber (425gr) solid projectiles with BC around 1.0 and the twist that has been working is 13 with an exit twist of around 5.5. At what point does increased mass and slower velocity actually hurt performance?

 

[CatShooter]

Seems like BC for each caliber is about as high as it can be. There might be room for a little improvement but very little. It takes mass to create very high BC. I doubt we will ever see a 6mm bullet with BC over .600 just because there is not enough mass. When Bryan Litz came out with the "Hybrid", it increased BC some. If we ever get to that point, looks like gain twist barrels might be the answer. Bartlein is making gain twist .375 barrels for very heavy for caliber (425gr) solid projectiles with BC around 1.0 and the twist that has been working is 13 with an exit twist of around 5.5. At what point does increased mass and slower velocity actually hurt performance?

Keep in mind that bullet companies do not derive BC the same ways - what is 0.700 in one company might be 0.620 or 0.790 with an other company... for the same bullet.

 

[amlevin]

Barret seems to have had some success with their .416 MSG bullet.

Bullet designers are working hard to make bullets that more closely resemble the Sears-Haack Body which is the most efficient aerodynamic shape. Essentially a bullet with "points" on both ends. Some are working with machined bullets rather than the traditional lead/copper alloy designs utilized today.

I don't think that bullet performance has been maxed out by any means. Just that the gains will be smaller and more expensive to achieve. It's bad enough to go out for a day of practice and realize with every shot you've just buried from $0.25 to $0.75 in the berm. Wait until you do that with a "machined bullet" that costs a multiple of that.

 

[Jeffvn]

+1 maximum performance has not been reached, at least for solids, but the marginal gains now are very expensive. I do beta testing for two different entities that are pushing the envelop using lathe-turned solids. The cost has been high, and the returns, although sometimes amazing, have not resulted in a commercially viable produce.... mostly because of cost. There are efforts being made to drive the cost down, but so far that has not been very successful. These are not the ultra-extreme super high twist projectiles that come from barrels dedicated to solid projectiles (yes I have also tested those projectiles for these same designers and developers). The projectiles I am now discussing are being fired from standard twist barrels, for example alternate shots from a 1:10 twist .308 and a 1:9 twist 7WSM & .284 Winchester.

Knowing where these bullets are on BC, I guess the question becomes one of acceptable cost for the marginal BC gain. How many folks are willing to spend 40-50% or more per bullet for a gain of 10-15% on the BC?

JeffVN

 

[CatShooter]

Any gains in BC's will not be achieved with longer and longer bullets - the twists needed to stabilize them become unmanageable.

Any meaningful, improvement in BC will come with denser cores - like Tungsten.

 

[dkhunt14]

Any gains in BC's will not be achieved with longer and longer bullets - the twists needed to stabilize them become unmanageable.

Any meaningful, improvement in BC will come with denser cores - like Tungsten.

That's about what I was thinking and I believe the gains will be small. Not sure about the accuracy though. Matt

 

[CatShooter]

Any gains in BC's will not be achieved with longer and longer bullets - the twists needed to stabilize them become unmanageable.

Any meaningful, improvement in BC will come with denser cores - like Tungsten.

That's about what I was thinking and I believe the gains will be small. Not sure about the accuracy though. Matt

There was a group in Oak Ridge, Tenn (Powell River Labs) about 25-30 years ago, that were making bullets with powdered Tungsten cores - the powdered tungsten was held together with a binder under pressure - so it was not near as dense as a solid Tungsten core would be... but they did get heavy bullets with higher BC's that shot in standard twists. But they were a $1.50+ each (and up) and that was in 1980 dollars (not today's useless wall paper ).

 

[Brians356]

But they were a $1.50+ each (and up) and that was in 1980 dollars (not today's useless wall paper ).

That's $4.30+ in wallpaper.

 

[Romulus]

BC's have not maxed out but the cartridges needed to propel such bullets (see Litz's chapter on projectile design about heavy-for-caliber bullets) and the twist rates required would relegate those builds to truly custom guns keeping projectile manufacturing in the quite expensive to non-affordable range. I shot GS Custom years ago, and while I loved the performance increase I just could not justify the $.

Any .30 Mag or .30 Super Mag would still have moderate performance in realistic ranges. The Berger 190 gr EOL .284 projectile is a great example - 7 LRM, 7 RUM, 7 Blaser, long barreled 7 Mags and still the performance in real world terms is a tradeoff. Thus the Snipe Tac and Allen Mag type offerings.

Now, if I were in the position of utilizing vast dispensable income I would love to invest R&E in some denser core materials, drive-bands, lubricants and all the cool technologies.

Now there are some practical examples of projectiles we have not even come close to MAXING out like .257, .277, & 0.325. Pragmatic examples that would offer high performance are the 257 Wby & the 270 WSM. However, the .325 WSM is too small a case to offer any advantage - An 8mm Lapua/Norma however would make the shorter barreled guns more viable for long range performance. 8) I asked Litz to produce a decent bullet in .257 and .325 but he said a while back that it is not viable in the market, and I have to concede it would be ineffecient R&E on the .325, but a lot of my generation would love to shoot good bullets out of .270 bores. Still these projectiles would just match our decently heavy for caliber bullets.

 

[Shynloco]

Keep in mind that bullet companies do not derive BC the same ways - what is 0.700 in one company might be 0.620 or 0.790 with an other company... for the same bullet.

That immediately strikes me as being a major problem for folks trying to learn some of the intricate details of ballistics (like me) when the language spoken is not uniform as to a basic component such as the BC of a bullet. It sure would be nice if the theories of competition (in terms of products manufactured) would at least have a common ground to build on other than "my bullet has a higher BC than yours."

Alex

 

[dkhunt14]

I see a lot of the companies are pretty close on their BC numbers but I see one or so that I feel inflates the number in order to sell bullets. Matt

 

[Sling]

The Von Karman profile seems the best being tested. By adding "lube" in the bands and with non-conventional rifling (18 lands & grooves) is being tested and shows promise. Bands actually decrease BC by adding drag but by using that kind of barrel, the bands are simply "washed" back into the grooves machined into the bullet. When a projectile becomes so long, they have hard time staying stabile once going subsonic. But by adding tungsten powder (about 10 micron)and a shorter bullet, we believe they will transition better. Bullet makers realized that by using brass, which is less weight than copper, BC was reduced. Example was the Barrett 416 bullet. Advertised as above .9, it actually is around .750 which seems high but not for such a big bullet. As technology advances, no doubt better bullets will be made but as what cost? Each bullet for my 408 Cheytac & 375 Cheytac is almost $2.00/pc + case, primer, & powder which is fine as they don`t get shot but few hundred times a year when the target is over 2500yds.

 

[338 Mollett]

Hey Sling long time no see !Prints are done on my case gotta decide if I wanna release them to the public or not .I think you pose a good question.Must drink on it ,will be in touch.

 

[Webster]

The only accurate way to determine BC is by Doppler Radar. It gives the true velocity at thousands at intervals down range. Very expensive. Most bullet makers determine BC by measuring drop at various ranges. You can find interesting articles on the web. Sierra and Lapua have used radar. I don't know if Sierra says which bullets were verified by radar.

http://en.wikipedia.org/wiki/Ballistic_coefficient
Near the bottom it talks about radar. It mentions that every bullet you shoot may have a different BC depending on yaw and when it stabilizes.

 

[mikecr]

Refine a way to heat the bases. Talk NBRSA & IBS into tracers..

 

[Steve Blair]

Most bullet makers determine BC by measuring drop at various ranges.

[br]
Most bullet makers compute B.C. by measuring velocity at various distances, not drop.

 

[Catfur]

Most bullet makers determine BC by measuring drop at various ranges.

[br]
Most bullet makers compute B.C. by measuring velocity at various distances, not drop.

From the crazy BCs published, I'd be a lot of BCs are generated by plugging optomistic numbers into a computer, which spits out a marketing number.

 

[Steve Blair]

Most bullet makers determine BC by measuring drop at various ranges.

[br]
Most bullet makers compute B.C. by measuring velocity at various distances, not drop.

From the crazy BCs published, I'd be a lot of BCs are generated by plugging optomistic numbers into a computer, which spits out a marketing number.

[br]
Nobody said they were accurate numbers, just the way they are measured. I think most European ammunition makers use Weibel dopplers, as do several government labs here in the U.S. A reasonable approximation of B.C. can be derived by measuring velocity at several distances under known conditions. Litz uses this method and I've found his G7 estimates to correlate reasonably well with my testing at 300, 600 and 1000 yards. I agree that doppler is the best method currently available.

 

[Sling]

Most bullet makers determine BC by measuring drop at various ranges.

[br]
Most bullet makers compute B.C. by measuring velocity at various distances, not drop.

From the crazy BCs published, I'd be a lot of BCs are generated by plugging optomistic numbers into a computer, which spits out a marketing number.

Your right. For example, GS Customs advertises BC being over 1.0 on alot of their bullets yet most have never been tested. Computer generated BC`s. They say for example it takes an 7 or 8 constant twist to be stabile. I promise they won`t be unless used in a Gain Twist barrel with an exit twist of at least 5.5 or 6.5. Then when they go subsonic, not stabile. A fellow shooter friend tried them in his 375 Cheytac with unsatisfactory results. Even the Lutz Moller projectile was a failure as soon as it exited the bore.

 

[Webster]

How do they measure velocity every 100 yards out to 1000 yards? Do you really think this is what they do. Cost for every bullet they make?
The BC is not a constant it is continually changing with the velocity down range. In the Sierra manual they give four BC for the 107 gr. Match King #1505 bullet depending on the velocity range it's in. Some long distance shooters complained to Sierra that there come ups didn't match the BC. Sierra recalculated the BC and apologized.