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Posted: 7/3/2017 10:54:30 PM EDT
I've always wondered why Liberty won't make this in a lighter grain for the 5.7. They make it in the 4.6 and they certainly could make a lot more calibers with this design and have a good thing going.
I was curious as to whether this super long bullet would stabilize in 5.7x28mm since both the FSN, P90, and PS90 both employ 1:9 twist barrels. If anything now you know and knowing is half the battle :D I wonder if I can source one of CMMG's older 1:7 twist barrels :D  M855A1 Bullet in 5.7x28mm? Will it work? |
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Posted: 7/4/2017 12:51:40 AM EDT
[#1]
ok, that was cool. did they stabilize out of the longer PS90 barrel?
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Posted: 7/4/2017 1:21:46 AM EDT
[#2]
Interesting. I would like to see them manufacture a lightened version for the 5.7.
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Posted: 7/4/2017 1:22:46 AM EDT
[#3]
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Posted: 7/4/2017 2:51:53 AM EDT
[#4]
I don't know what the BC is or if it's a "G1 or G7", but it seems to indicate at 1300 fps we need 1:7 :D
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Posted: 7/4/2017 6:42:58 AM EDT
[#5]
Quote HistoryHard to do if you don't know the round's specific gravity, and then, the distribution will be funky due to the 20ish gr insert in the nose and the Cu slug in the back.
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Posted: 7/4/2017 6:37:51 PM EDT
[#6]
Quote HistoryQuoted:
Hard to do if you don't know the round's specific gravity, and then, the distribution will be funky due to the 20ish gr insert in the nose and the Cu slug in the back. |
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Posted: 7/4/2017 6:41:26 PM EDT
[#7]
Quote HistoryQuoted:
Hard to do if you don't know the round's specific gravity, and then, the distribution will be funky due to the 20ish gr insert in the nose and the Cu slug in the back. EDIT: 1.33 - marginally stable |
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Posted: 7/5/2017 2:03:06 AM EDT
[#8]
Quote HistoryQuoted:
All you really need is the length. If it is above 1.0, it should be stable. EDIT: 1.33 - marginally stable It's like calculating compression with a vehicle engine...but there is massive valve-overlap. Your static compression calculation will not reflect real world compression ratios. |
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Posted: 7/5/2017 2:03:43 AM EDT
[#9]
Quote HistoryQuoted:
You can get pretty darn close with a sectioned picture of the projectile and some simple volume equations by taking a rough estimate of the sizes and breaking them into simple geometric shapes. You won't get the exact answer but close enough to know if you are on the border line with you projected velocities and factory availible twist rates. |
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