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High BC bullets?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/19/2008 at 15:07
trigger29 View Drop Down
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I was just wondering if higher BC bullets are less affected by atmospheric conditions? Currently my .277cal 150gr. bullet has a BC of .345 and a difference of 20 degrees, and 2 in. barometric pressure will change my point of impact over 6" at 600 yards. I was wondering if a higher BC flatter shooting bullet would be less affected?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/19/2008 at 16:24
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more than likely
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/19/2008 at 18:46
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Originally posted by trigger29 trigger29 wrote:

I was just wondering if higher BC bullets are less affected by atmospheric conditions? Currently my .277cal 150gr. bullet has a BC of .345 and a difference of 20 degrees, and 2 in. barometric pressure will change my point of impact over 6" at 600 yards. I was wondering if a higher BC flatter shooting bullet would be less affected?
.............Yes! The higher the bullet BC, the better it will fly given the same atmospheric conditions.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/23/2008 at 15:36
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In general the bullet with the higher BC will be more consistent, but the difference is not generally enough to worry about within the same caliber and bullet class.

It works like this: As a bullet passes through the atmosphere, the air affects its flight path. The more aerodynamic bullet is the less it is affected by aerodynamic forces, so if it is less affected by those forces in general then changes in those forces are less significant as well.

If a 20 degree rise in temperature changes your impact by 1 MOA, then a bullet with a better (higher) BC might only change .95 MOA.


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/24/2008 at 17:18
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I am thinking of going from a bullet with a BC of .344 to a BC of .545. I was hoping the results would be more signifcant with that big of change.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/25/2008 at 21:05
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This is one of those cases where you have to have an idea of what range you intend to shoot at before you can determine what bullet will suit your purposes.

Changing from a .344 to a .545 will have a significant influence on the flight of the round. The greatest impact will be velocity retention. However, I am assuming that the .545 round will be much heavier and will start out at a significantly lower velocity.

To figure total drop, it is helpful to compute flight time or average velocity of the round to your target distance. Ideally, you want to minimize your time in flight. Faster lighter bullets do better at this at short ranges, heavier tend to do better at longer ranges.

Ballistics folks spend a lot of time balancing velocity and BC, which tends to be inversely related to velocity because of mass.  My recommendation would be to not worry about the specific BC of the bullet, rather use some ballistics software, a chronograph, and some reloading to see if you can tune for a shorter flight time at your expected ranges. Everything else will fall into place.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2008 at 10:57
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Generally speaking a heavier bullet will have higher BC, but more importantly it will have greater sectional density, this is most desirable too me, greater sectional density = greater penatration. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2008 at 13:50
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the main reason the heavy bullets have higher b.c is because they are longer, which in turn makes the s.d higher too, i shoot short ranges so b.c doesnt mean a lot to me, where the s.d does.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2008 at 14:29
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I agree, all of my shooting is under 300 yds so BC doesn't really does take effect.  What I like about high SD is that I can chose a less expensive "vanilla" type bullet and not worry about it comming apart

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/26/2008 at 14:36
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Quote the main reason the heavy bullets have higher b.c is because they are longer, which in turn makes the s.d higher too, i shoot short ranges so b.c doesnt mean a lot to me, where the s.d does.

Partially true.  For a given caliber, a heavier bullet has a higher bc partly because it is longer and "slipperier".  "Fineness of form" or how sleek a bullet is partly driven by length, but there are other considerations such as length shape of the ogive and length and shape of the boattail.

The other consideration is that mass itself drives bc.  A conventional leadcore bullet will have a better bc than a pure copper bullet of identical caliber and shape.  Another example of mass driving bc is that the G1 Standard projectile, weighs one pound and has a very "un-sleek" profile (almost a round nose and no boat tail) yet has a bc of 1.00.  My .224 caliber 90gr VLD's with all tricks of modern bullet design provides at best has a bc of around .550

In bc, mass matters.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/06/2008 at 16:33
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Originally posted by Graysteel Graysteel wrote:

This is one of those cases where you have to have an idea of what range you intend to shoot at before you can determine what bullet will suit your purposes.

Changing from a .344 to a .545 will have a significant influence on the flight of the round. The greatest impact will be velocity retention. However, I am assuming that the .545 round will be much heavier and will start out at a significantly lower velocity.

To figure total drop, it is helpful to compute flight time or average velocity of the round to your target distance. Ideally, you want to minimize your time in flight. Faster lighter bullets do better at this at short ranges, heavier tend to do better at longer ranges.

Ballistics folks spend a lot of time balancing velocity and BC, which tends to be inversely related to velocity because of mass.  My recommendation would be to not worry about the specific BC of the bullet, rather use some ballistics software, a chronograph, and some reloading to see if you can tune for a shorter flight time at your expected ranges. Everything else will fall into place.

 
Actually the bullets are the same weight. Currently I am shooting 150 gr. Winchester powerpoints. I was looking at loading 150 Berger VLD's. The winchesters seem to have a very low BC for this caliber of bullet.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/13/2008 at 10:06
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In that case, the bullet with the higher BC will loss less velocity over any distance, and should always have a higher average speed. If cost isn't and issue, go with the .545s.

Just my two cents.
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