The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Which Bullet Manfacturer Publishes Accurate Ballistic Coefficients?Go | New | Find | Notify | Tools | Reply | |
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I’m sometimes puzzled by published ballistic coefficients (BCs). For example, published BCs from SPEER seem exaggerated to me, especially when compared to SIERRA BCs, which are more conservative – yet, the bullet designs from both manufacturers seem essentially identical. Nosler BCs seem reasonable. What is your opinion? Moreover, have any of you actually measured various bullet BCs and compared your findings with published BCs? Would you be willing to share those findings with us? Regards and happy/safe hunting/shooting, AIU. | ||
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There have been some published articles by Rick Jamison I think. In general all of his numbers were less than the factory data. Some of the Nosler data has to be way off. I don't trust anything that Barnes says. That link is around here somewhere.  Join the NRA | |||
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I've read that bullets have different BCs at different velocities. Maybe it's a matter of choosing the most favorable number versus the most likely to be found in the real world of handloading? "Experience" is the only class you take where the exam comes before the lesson. | |||
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the only way to know FOR SURE, what YOUR BC is in YOUR RIFLE is to run the drop chart after getting a proven avg MV. THEN, after inputting the elevation, temp, zero range, bullet weight, "supposed" BC, etc, you run your chart and then go back to the range. Now, put that load on paper strating at say 300yds. then 400yds, then 500yds, etc. When the bullet hits higher than the stated POI from your chart, you will need to adjust the BC valua up, then re-run the chart once the impacts on the new chart match what you are seeing in reality. Likewise, if the POI is lower than the first chart says it should be, you will need to adjust your BC value down, and re-run the chart again until the real POI matches the new chart. This should be done at several longer distances so that the "best" and most "workable" value of BC is put into the final chart. BC changes with velocity, so unless you set chronographs at various distances, you will only ever be "close" to exact, after that it is a few clicks either way. You KNOW the MV, the temp, the altitude, and the zero range, and the bullet weight. The only variable is the BC, which is up to you to prove in your rifle barrel. Difficulty is inevitable Misery is optional | |||
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Sierra is the only manufacturer which lists a different BC depending on the velocity. Personally, I don't place any value in any of the published (by the manufacturers) BC's. | |||
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Ricciardelli, hit it on the head. Many load manuals list static ballistic coeffecients, whereas the data that Savage 99 provided shows BC at a given velocity. This is similar to the method Sierra uses, but they cite a velocity range at which the BC will be obtained. I find one method about as reliable as another if you take into account that these are competing companies that may feel a need to list BC in a light that favors their product. All I ask is that I be given an accurate static BC, I can take it from there. But some of the static BC's can be overly optimistic, and once in awhile they are published incorrectly and have to be revised. The last example I'm aware of was when NOSLER published BC for the .264 100 grain Partition. It looked too good to be true and that turned out to be the case. It was revised to a more realistic level. Likewise, I take data with a grain of salt when one manufacturer is comparing any load data with competing products listed. Somehow the manufacturer providing the data always manages to come out on top!  "No one told you when to run; you missed the starting gun." | |||
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Correct. In addition, there are several "standard projectiles" to which a bullet's performance can be compared to determine a B.C. number. Naturally, the performance of your bullet compared to different "standard projectiles" would be different, even at the same velocity. "Bitte, trinks du nicht das Wasser. Dahin haben die Kuhen gesheissen." | |||
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I believe a very effective means of arriving at a B.C. for a given bullet would be to compare the MV to the remaining velocity at several known distances, to determine how much velocity was lost. This method gives you a figure for ability to overcome air resistance, and that's all a B.C. is - the PERCENTAGE of air resitance overcoming ablitiy of your projectile VS the "standard projectile", which has a B.C. of "1". For example, a B.C. of .250 meanns that your bullet overcomes air resistance onl;y one-fourth as well as does the standard projectile upon which the tables are based. Of course, the results will have to be corrected to reflect the deviation of temoperature and presssure from standard figures("density altitutde") to be meaningful. If you have access to one of the doppler-effect type chronographs, the deceleration of the projectile can be recorded throughout its flight, permitting the calculation of the actual B.C. at any point in the flight of the bullet (or artillery shell). "Bitte, trinks du nicht das Wasser. Dahin haben die Kuhen gesheissen." | |||
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From an earlier post: I recently tested a few 30 Cals over the Oehler at 5 and 205 yds. Not an especially sophisticated test and a small sample size so don't put faith in these numbers down to the last .001 or anything, but they are enough to give me a pretty good idea. 180 TSX measured .411 180 Scirocco measured .539 200 AccuBond .550 All numbers corrected to ICAO. Like I said, I'd expect the averages to shift a little had I done 20-shot strings, etc. The Scirocco launched at the same velocity put about 100 fps on the TSX at only 200 yds at 4400 ft altitude (the difference would be greater closer to sea level). In this test the Nosler fell just a bit under advertised and the Swift was a bit better than advertised but both were in the ballpark. The Barnes tested even lower than I expected (I was guessing it would be in the .45 range). | |||
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I think the BC's on the NOrth Fork bullets are probably the most accurate, since he doesn't list any. A shot not taken is always a miss | |||
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El Dequello, you are basicaly doing the same thing I am doing. Instead of adjusting the BC to find correct POI, you are adjusting BC to get correct Velocity at the extended ranges. Both figures are changed as the BC value is adjusted and will be symbiotic, Right? Difficulty is inevitable Misery is optional | |||
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Seems right to me!! "Bitte, trinks du nicht das Wasser. Dahin haben die Kuhen gesheissen." | |||
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The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Which Bullet Manfacturer Publishes Accurate Ballistic Coefficients?
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