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264" 130g scirocco advertised BC

 
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  #1  
Old 05-05-2011, 05:30 AM
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264" 130g scirocco advertised BC

Was looking over swift sciroccos the other night and came across something that doesn't seem right to me.

They claim a .571 BC from a 130g .264" bullet, how the hell do they come up with that??? Thats higher then any bullet that I can really think of besides the 140g VLD/AMAX, and its really not to far off of those. Beats the pants off any other 130 and 140 bullet reguardless. How do they gain almost a whole .1 value greater??

The 129g SST is pretty sleek and slender itself for a lowly .485

The 130g AB is also advertised at about .488

Anyone care to share thoughts or experiences with this bullet?? Love to hear it.

Think I'm going to make me a phone call to Swift tomorrow while I'm at it, pick there brain a bit...
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Old 05-05-2011, 05:53 AM
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Re: 264" 130g scirocco advertised BC

The bc's of the 264 seem to run on the high end. Even the black hills gold ammo is advertised at 2750 and a BC of .58 with a 142 grain sierra matchking.
I would love for someone with a great understanding of this to add more.
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Old 05-05-2011, 07:31 AM
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Re: 264" 130g scirocco advertised BC

Keep in mind that the jacket is VERY thick, which allows a very long, streamlined bullet.

I have talked to Brad at Swift a couple of times, it appears that they are sticking to their guns on the BC of that bullet. He told me that a little jump was better, .030-.050. Brad commented that this was possibly the best bullet they have made to date.

They have been shooting for the purpose of a new manual & only mentioned RL powders to me, but most 264 shooters get best results with Retumbo.

I have a new Ruger Number 1 264, I will try them soon.
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Old 05-05-2011, 08:20 AM
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Re: 264" 130g scirocco advertised BC

I'm using the 130 gr Scirrocco II in my 6.5 rem mag (26" Douglas barrel 1 in 8). First Scirrocco I have gotten to shoot good in any rifle. There are a couple of bullets that shoot a little better but this is typical for me




Anyway, I have a Zeiss 4.5x14x44 with the RapidZ800 reticle on it. The Zeiss website calculator says that with the .571 BC and a velocity of ~3200 fps then I could just set it on ~14 power. So I took my load at ~3200 fps, zeroed it at 200 yds and then shot it at 300 and 400 yds. The 14 power didn't work out for me. Had to set the power back down to ~12.5 power to bring the POI up to POA.

That indicates to me that the advertised BC is not correct or the reticle/calculator on the Zeiss is not.

Only did this once so need to go back and reshoot 200 yds, then 300 yds, 400 yds and 600 yds to verify.
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Old 05-05-2011, 08:39 AM
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Re: 264" 130g scirocco advertised BC

Quote:
Originally Posted by remingtonman_25_06 View Post
Was looking over swift sciroccos the other night and came across something that doesn't seem right to me.

They claim a .571 BC from a 130g .264" bullet, how the hell do they come up with that??? Thats higher then any bullet that I can really think of besides the 140g VLD/AMAX, and its really not to far off of those. Beats the pants off any other 130 and 140 bullet reguardless. How do they gain almost a whole .1 value greater??

The 129g SST is pretty sleek and slender itself for a lowly .485

The 130g AB is also advertised at about .488

Anyone care to share thoughts or experiences with this bullet?? Love to hear it.

Think I'm going to make me a phone call to Swift tomorrow while I'm at it, pick there brain a bit...
I measured a G1 BC of .491 for that bullet. G7 BC is .251.
book

It's got a decent ogive design, but a poor (short and steep) boat tail for base drag reduction. Certainly not a design that could possibly produce a .571 average G1 BC. Even at 3000 fps, the G1 BC is just .515, degrading to .453 at 1500 fps.

A thick jacket for a long bullet...? Sure it makes the bullet longer, but that doesn't mean high BC. Lengthening the nose and tail will reduce drag, but lengthening the bearing surface does nothing for drag so it's irrelevant.

None of my analysis included group shooting (precision) testing so I can't comment on that. They may be extremely precise, but the BC claim is not accurate.

-Bryan
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Old 05-05-2011, 11:36 AM
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Re: 264" 130g scirocco advertised BC

The .58 BC I referred to earlier is Black hills specs for the 6.5x284 norma with the 142gr matchking. Didn't know if that made any difference. Still seems a bit on the high side.
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Old 05-05-2011, 07:32 PM
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Re: 264" 130g scirocco advertised BC

Quote:
Originally Posted by bsl135 View Post
I measured a G1 BC of .491 for that bullet. G7 BC is .251.
book

It's got a decent ogive design, but a poor (short and steep) boat tail for base drag reduction. Certainly not a design that could possibly produce a .571 average G1 BC. Even at 3000 fps, the G1 BC is just .515, degrading to .453 at 1500 fps.

A thick jacket for a long bullet...? Sure it makes the bullet longer, but that doesn't mean high BC. Lengthening the nose and tail will reduce drag, but lengthening the bearing surface does nothing for drag so it's irrelevant.

None of my analysis included group shooting (precision) testing so I can't comment on that. They may be extremely precise, but the BC claim is not accurate.

-Bryan
Good info, thanks!! I did not mean that a long bullet Guaranteed a good BC, merely that it increased the odds with all else equal. Thanks for supplying real numbers, may actually be close to the 130 Accubond that is rated at .488 I think. Have you tested that one.
Looks like the 130 & 140 Berger look even better now.
Thanks
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