Posted: 2/27/2012 7:26:04 AM EDT
| Does any one know the equation of how to work out the G1 BC of a bullet? I have some bullets with an unkown BC, & before any one suggest's I cant ask the manufacturer's its complicated. |
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There are calculators out there but you need to know near and far velocities or time of flight etc...
Could be fun trying it out... Chrono at your end and one at the target.... 
Link Link BC Estimator |
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http://tmtpages.com/calcbc/calcbc.htm
I used this one for some pistol bullets that had no BC data. Not sure how good it is but ut helped me out when I needed it |
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http://tmtpages.com/calcbc/calcbc.htm I used this one for some pistol bullets that had no BC data. Not sure how good it is but ut helped me out when I needed it That's a bit similar to the 'estimator' I linked to......
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There are calculators out there but you need to know near and far velocities or time of flight etc... Could be fun trying it out... Chrono at your end and one at the target....
That is the best way. I only know of 2 people that have done that, John Carmichael and Derrick Martin. To get around the ability to reliably shoot between the screens at distance, they both did away with them and made ip some start/stop screens with thin aluminium foil backed Celotex (insulation panels) with circuitry attached. The bullet being long enough to pass through the front and rear and make a momentary circuit bridge. Personally I think there is too much written into all this and would lean towards a similar bullet and glean the BC data from that. Remember though sensation seekers that it is not the bullets BC you are measuring but the air the bullet is moving aside |
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Ballistic Coefficient = Sectional Density x Form Factor
where: Sectional Density = Bullet weight (in pounds) / Bullet Diameter (in inches) squared The Form Factor is derived from the shape of the bullet. For a G1 projectile it's 1.926 Form factors for other bullet shapes: FMJBT blunt nose 1.739 FMJBT sharp nose 1.818 Lapua Scenar 2.160 SMK long boattail 1.961 SMK short boattail 1.869 Berger VLD 2.000 Is your bullet on here: Bullet database |
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Ballistic Coefficient = Sectional Density x Form Factor where: Sectional Density = Bullet weight (in pounds) / Bullet Diameter (in inches) squared The Form Factor is derived from the shape of the bullet. For a G1 projectile it's 1.926 Form factors for other bullet shapes: FMJBT blunt nose 1.739 FMJBT sharp nose 1.818 Lapua Scenar 2.160 SMK long boattail 1.961 SMK short boattail 1.869 Berger VLD 2.000 Is your bullet on here: Bullet database Thanks for all your input, No this bullet isnt on any data base at the moment as its still being tested. The bullet is similar to the one that the Cheytac M200 LRSS shoots but smaller. |
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Ballistic Coefficient = Sectional Density x Form Factor where: Sectional Density = Bullet weight (in pounds) / Bullet Diameter (in inches) squared The Form Factor is derived from the shape of the bullet. For a G1 projectile it's 1.926 Form factors for other bullet shapes: FMJBT blunt nose 1.739 FMJBT sharp nose 1.818 Lapua Scenar 2.160 SMK long boattail 1.961 SMK short boattail 1.869 Berger VLD 2.000 Is your bullet on here: Bullet database Thanks for all your input, No this bullet isnt on any data base at the moment as its still being tested. The bullet is similar to the one that the Cheytac M200 LRSS shoots but smaller. A Shite Tac? 
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Ballistic Coefficient = Sectional Density x Form Factor where: Sectional Density = Bullet weight (in pounds) / Bullet Diameter (in inches) squared The Form Factor is derived from the shape of the bullet. For a G1 projectile it's 1.926 Form factors for other bullet shapes: FMJBT blunt nose 1.739 FMJBT sharp nose 1.818 Lapua Scenar 2.160 SMK long boattail 1.961 SMK short boattail 1.869 Berger VLD 2.000 Is your bullet on here: Bullet database Thanks for all your input, No this bullet isnt on any data base at the moment as its still being tested. The bullet is similar to the one that the Cheytac M200 LRSS shoots but smaller. A Shite Tac? I dont know, ive never seen one up close, they say the 408 round is better than the 338 & .50? |
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CheyTac haven't earned themselves a very good name over the last few years with that whole .408 thing.
It appears all isn't as it seems. There's a guy on here from the AMU, Epraslick, Emil Praslick. He's a member of the US Palma team and a well established shooter in the US of A. He was part of the team that was tasked with evaluating that thing. The story IIRC, Cheyanne Tactical turn up at the range with their system and set it up to fire at the target at 1000yds. They plug in the laptop, do some calculations and fire a shot.............it misses. They they go into a huddle for 10 mins and then announce that they forgot to calculate the earths rotation  , fire a second shot.......and miss.
The brass say "Thank you gentlemen, We think we've seen enough for today". Cheyanne Tactical get their coats. Then they say that there are many militaries throughout the world that have adopted it, when actually none have. Then they announce that they will sell it to the US public, but only in a less accurate form than what is offered to the Military.......so the American shooting community do what they do best and round on them. Needless to say their reputation suffered after that. Rob the Diggle sniper Hunter had one built and 3 people from this forum saw him repeatedly miss a 6' x 6' steel plate at 600yds at Warcop before he packed it away and went home |
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CheyTac haven't earned themselves a very good name over the last few years with that whole .408 thing. It appears all isn't as it seems. There's a guy on here from the AMU, Epraslick, Emil Praslick. He's a member of the US Palma team and a well established shooter in the US of A. He was part of the team that was tasked with evaluating that thing. The story IIRC, Cheyanne Tactical turn up at the range with their system and set it up to fire at the target at 1000yds. They plug in the laptop, do some calculations and fire a shot.............it misses. They they go into a huddle for 10 mins and then announce that they forgot to calculate the earths rotation , fire a second shot.......and miss.
The brass say "Thank you gentlemen, We think we've seen enough for today". Cheyanne Tactical get their coats. Then they say that there are many militaries throughout the world that have adopted it, when actually none have. Then they announce that they will sell it to the US public, but only in a less accurate form than what is offered to the Military.......so the American shooting community do what they do best and round on them. Needless to say their reputation suffered after that. Rob the Diggle sniper Hunter had one built and 3 people from this forum saw him repeatedly miss a 6' x 6' steel plate at 600yds at Warcop before he packed it away and went home I don't think I'll be buying one of those then!!
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Ballistic Coefficient = Sectional Density x Form Factor where: Sectional Density = Bullet weight (in pounds) / Bullet Diameter (in inches) squared The Form Factor is derived from the shape of the bullet. For a G1 projectile it's 1.926 Form factors for other bullet shapes: FMJBT blunt nose 1.739 FMJBT sharp nose 1.818 Lapua Scenar 2.160 SMK long boattail 1.961 SMK short boattail 1.869 Berger VLD 2.000 Is your bullet on here: Bullet database That bullet database was just what I needed! Cheers 
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CheyTac haven't earned themselves a very good name over the last few years with that whole .408 thing. It appears all isn't as it seems. There's a guy on here from the AMU, Epraslick, Emil Praslick. He's a member of the US Palma team and a well established shooter in the US of A. He was part of the team that was tasked with evaluating that thing. The story IIRC, Cheyanne Tactical turn up at the range with their system and set it up to fire at the target at 1000yds. They plug in the laptop, do some calculations and fire a shot.............it misses. They they go into a huddle for 10 mins and then announce that they forgot to calculate the earths rotation , fire a second shot.......and miss.
The brass say "Thank you gentlemen, We think we've seen enough for today". Cheyanne Tactical get their coats. Then they say that there are many militaries throughout the world that have adopted it, when actually none have. Then they announce that they will sell it to the US public, but only in a less accurate form than what is offered to the Military.......so the American shooting community do what they do best and round on them. Needless to say their reputation suffered after that. Rob the Diggle sniper Hunter had one built and 3 people from this forum saw him repeatedly miss a 6' x 6' steel plate at 600yds at Warcop before he packed it away and went home I don't think I'll be buying one of those then!!
That Cheytac been on the "for sale" board http://www.offasrifleclub.com/for_sale.htm for quite a long time (bottom of the page). It comes with .338 lap mag barrel as well. |
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Ballistic Coefficient = Sectional Density x Form Factor where: Sectional Density = Bullet weight (in pounds) / Bullet Diameter (in inches) squared The Form Factor is derived from the shape of the bullet. For a G1 projectile it's 1.926 Form factors for other bullet shapes: FMJBT blunt nose 1.739 FMJBT sharp nose 1.818 Lapua Scenar 2.160 SMK long boattail 1.961 SMK short boattail 1.869 Berger VLD 2.000 Is your bullet on here: Bullet database Thanks for all your input, No this bullet isnt on any data base at the moment as its still being tested. The bullet is similar to the one that the Cheytac M200 LRSS shoots but smaller. A Shite Tac? I dont know, ive never seen one up close, they say the 408 round is better than the 338 & .50? Saw a Shite-Tac at Warcop being 'zeroed'. There was a large screen the size of a tank that it couldn't hit consistently at about 500m. Mousegunner and BunnyAssassin were there as well and may have more exact details, but needless to say the whole zeroing process didn't happen and these machined bullets were meant to have a BC of nearly 1! |
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Ballistic Coefficient = Sectional Density x Form Factor where: Sectional Density = Bullet weight (in pounds) / Bullet Diameter (in inches) squared The Form Factor is derived from the shape of the bullet. For a G1 projectile it's 1.926 How does that cope with different speeds? Some manufacturers will quote different BCs at different speeds for the same bullet, I can see no provision for speed in that equation. |
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Brian Litz - (Bergers' bullet designer) has some info:
Brian Litz site |