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Mythbusting .695 BC 120gr 6.8mm bullet possible?

So in the interest of gaining knowledge I wanted to see what some of you guys with a little more know-how feel about something that recently came up on a small local forum.

There is a gentleman that has a 6.8mm custom bullet with .695” BC. Custom or not this seems a bit off to me. I’m very familiar with some of the exotic custom lathe tunred offerings from Lost River, GS and Lutz Moeller but this just seems a little on the high side. He has yet to post a picture of the bullet which further deepens my skepticism, also he won’t answer any specific questions on how he arrived at the .695 number, what the overall length is, bearing surface length ect....... very frustrating when looking to expand ones knowledge base.

The bullet is described as a 120 grain Tungsten Ultra Low Drag Tipped Secant Ogive bullet and that it was swaged by a man in Louisiana. Now it is reportedly being fired at around 4200 FPS from a 300 WBY based wildcat. The bbl of the rifle is a a 1-11 twist and is 34.5” in length.


From what I remember the Lost River high BC 135gr J36’s needed a 1-10 twist or better . Considering the Lost River bullet had a claimed BC of over .7 I guess I could see how there might be a possibility that this bullet could do close to .7 with its very high velocity but it certainly wouldn’t think it could hold that BC for very long, certainly not long enough to have the 32” of wind drift @ 1000 (10 mph direct cross) .

Sure wish I could see a picture of it, sounds cool, what do you guys think?
 
Based on the info you provided the answer yes.

Yes you can make a 120gr .277” bullet with a G1 .695 BC. It would have to be turn. I would guess if it dose exist it is a tungsten sabot bullet like the now discontinued Barnes MRX bullets. Also, I'm guessing the bullet would be around 1.4” long with a form function of .320 and a specific gravity of around 10.0.

At 4200fps the bullet would have a marginal stability form Miller's formula of 1.109 (minimal is 1.3) and Greenhill's formula yields a minimum twist rate of 11.9.
 
glo said:
Based on the info you provided the answer yes.

Yes you can make a 120gr .277” bullet with a G1 .695 BC. It would have to be turn. I would guess if it dose exist it is a tungsten sabot bullet like the now discontinued Barnes MRX bullets. Also, I'm guessing the bullet would be around 1.4” long with a form function of .320 and a specific gravity of around 10.0.

At 4200fps the bullet would have a marginal stability form Miller's formula of 1.109 (minimal is 1.3) and Greenhill's formula yields a minimum twist rate of 11.9.


Very cool, do you by chance have any pics of such pills?
 

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