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  #1  
Old 01-25-2020, 02:33 PM
DesertRat9 DesertRat9 is offline
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SWC vs RN aerodynamics

From reading this forum and others it seems the preponderance of experience is the SWC are more accurate than RN for same bullet weight. 1911 rounds are subsonic. SWC in general have lower BC than RN, so theoretically the RN has a flatter trajectory. It seems to me that the CM for a RN bullet is further forward than for a SWC, so wouldn't that make the RN more stable, and thus more accurate? What am I missing?

I don't care about the shape or crispness of the hole in the target.
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  #2  
Old 01-25-2020, 03:46 PM
david_root2000 david_root2000 is online now
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At pistol distances BC should not matter. SWC are usually more accurate than RN in 45 for me.

Hornady says BC of SWC is .070
BC of LRN is .207 which is a big difference. Did not figure out how much it matters at 25 or 50 yards. You might find Hornady ballistic charts for pistols on the internet.

David
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  #3  
Old 01-25-2020, 03:50 PM
jtq jtq is offline
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Here's an article that doesn't address aerodynamics, but does show how a flat nose vs round nose is affected in thicker medium such as flesh.

http://www.gsgroup.co.za/articlepvdw.html
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  #4  
Old 01-25-2020, 09:27 PM
ClarkEMyers ClarkEMyers is offline
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The difference between spin stabilized and air stabilized.

A shuttle cock does benefit from weight forward but a bullet goes confined through the barrel rotating about center of form and hits the air where it's suddenly rotating about center of mass. Consider the period before the bullet goes to sleep as the saying goes. See Bryan Litz and many others who have written on the general subject.
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  #5  
Old 01-26-2020, 10:49 AM
flechero flechero is online now
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aerodymnamic doesn't necessarily equal consistent/accurate

An aerodynamic bullet may fly faster, further but doesn't mean it will hit the X more consistently. My guess is that the symmetry (or lack thereof) in round nose itself is the issue. (the old adage of "there is no such thing as a perfect circle") As a bullet spins, the nose pulls one direction more then the others and/or the air resistance on the curve of the nose isn't equal. (creating wobble) Where the flat nose and shoulder of the SWC are more symmetrical and allow a more consistent flight track... (less wobble)

Although, most of us need a ransom rest to tell the difference between well made bullets.
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  #6  
Old 01-26-2020, 11:11 AM
jtq jtq is offline
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This talks about hollow points, but it mentions the wider meplat which is also the case with the semi-wadcutter

https://en.wikipedia.org/wiki/Hollow-point_bullet
Quote:
In target shooting, they are used for greater accuracy due to the larger meplat. Although a pointed bullet has a higher ballistic coefficiency (BC), it's also more sensitive to bullet harmonic characteristics and wind deflection, thus making hollow point bullets consistently more accurate and predictable.
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  #7  
Old 01-26-2020, 12:36 PM
david_root2000 david_root2000 is online now
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I looked it up. At 50 yards there is a difference using Hornady swaged lead bullets.

SWC is 754 @ 50 yards
LRN is 803.

Both 230 grain bullets, both starting at 830 fps.

David
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  #8  
Old 01-27-2020, 11:09 AM
hardluk1 hardluk1 is offline
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Bottom line the best 50 yards bullseye currently are HP designes but SWC in 185 & 200gr are still very good . So if shooting tight groups is wanted start with nosler or zero 185 and 200gr HP then SWC and FN over a round nose regardless of the SD or velocity of the RN
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  #9  
Old 01-27-2020, 08:44 PM
Big Pete10 Big Pete10 is offline
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I switched from cast 200 SWC to cast 200 RN when I started shooting revolver. I have not tested for accuracy at 50 yards with a machine rest so I can't say the RN is as accurate as the SWC BUT, out to 25 yards shooting them I can't tell the difference in accuracy. I suspect that a quality RN will shoot with the SWC but it will never cut the nice hole in paper like the SWC. Standing on my hind feet at 25 yards the RN shoots with the SWC.
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  #10  
Old 01-28-2020, 06:01 AM
david_root2000 david_root2000 is online now
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Quote:
Originally Posted by DesertRat9 View Post
SNIP
I don't care about the shape or crispness of the hole in the target.
I get better accuracy out of a SWC in 45 and a RN in 38.

David
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  #11  
Old 01-29-2020, 12:23 AM
JayhawkNavy02 JayhawkNavy02 is online now
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Quote:
Originally Posted by hardluk1 View Post
Bottom line the best 50 yards bullseye currently are HP designes but SWC in 185 & 200gr are still very good . So if shooting tight groups is wanted start with nosler or zero 185 and 200gr HP then SWC and FN over a round nose regardless of the SD or velocity of the RN
Zero 185 gr or Nosler. FWIW, Zero or Nosler make a 200 gr JHP for 45 ACP.
Of the two Zero seems to be better out of the Ransom and HEG rest.

Quote:
Originally Posted by david_root2000 View Post
I get better accuracy out of a SWC in 45 and a RN in 38.
Out of a Revolver?
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Last edited by JayhawkNavy02; 01-29-2020 at 07:46 AM.
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  #12  
Old 01-30-2020, 05:17 PM
DesertRat9 DesertRat9 is offline
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I think the rotational moment of inertia is higher for the SWC than for the RN, if both are lead. I didn't do the integration but based on cross section it looks that way. So SWC is more stable during flight. I suspect aero has minimal effect at hand gun distances, as was pointed out above.
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