G7 to G1 conversion

[nealm66]

Is there a simple way to convert g7 to g1? I'm helping a friend do load work up on a hammer bullet and he wants to have a turret made for his huskemah ( not sure I spelled that right) . It's only for distance out to 600 so I'm hoping the box g7 will be close and I'll double check drop but they want trued g1 bc for turret info

 

[Beluebow]

G7/.512=G1

 

[ShtrRdy]

G7/.512=G1

I don't think it's that simple but I might be over complicating it in my mind.

The G1 and G7 numbers come from the drag curves of the bullet. A drag curve is basically the coefficient of drag at a velocity. While the conversion number 0.512 may be true for some velocity on the curves it may not be the best choice to have a custom turret made.

 

[Beluebow]

I don't think it's that simple but I might be over complicating it in my mind.

The G1 and G7 numbers come from the drag curves of the bullet. A drag curve is basically the coefficient of drag at a velocity. While the conversion number 0.512 may be true for some velocity on the curves it may not be the best choice to have a custom turret made.

He asked for simple, if you have a better answer I'm all ears.

My advice is forego having a turret made. But he didn't ask for that advice.

 

[waveslayer]

He asked for simple, if you have a better answer I'm all ears.

My advice is forego having a turret made. But he didn't ask for that advice.

I second that. Turret or dialing is different because?.... skip the turret BS and tune your calculator to your load , because BC's are dependent on YOUR gun and Velocity... so the box BC is not good data

 

[nealm66]

Ya, he's used the system for quite a while and loves it. I told him I could probably make a piece of tape with the drops and windage but he wants the turret. I'm just not sure how to give trued g1 bc and hammers only list estimated g7. Can a guy use one of those lab radar things to get g1?

 

[waveslayer]

I guess find a G7 bullet that has the same BC and check if it has a G1 listed.. again it won't be accurate

 

[nealm66]

I guess find a G7 bullet that has the same BC and check if it has a G1 listed.. again it won't be accurate

I was thinking that as well and then make the corrections based on drop? He's only shooting inside 600 with this rifle. It's a slow twist 7mm rm and he's going to try the 131 heavy hammer. He shoots one deer and one elk every year

 

[nealm66]

I'm guessing it would be very similar to Barnes but open to suggestions

 

[asd9055]

The little understanding I have about Ballistic coefficients tells me that you should use the appropriate one for the type of bullet. I do not believe G1 would be appropriate for hammers. But again, my understanding is limited...

 

[Coyote Shadow Tracker]

Ya, he's used the system for quite a while and loves it. I told him I could probably make a piece of tape with the drops and windage but he wants the turret. I'm just not sure how to give trued g1 bc and hammers only list estimated g7. Can a guy use one of those lab radar things to get g1?

Bullet manufacture can usually give you the G-1 and G-7. You can't get the BC from a LabRadar. BC comes from many calculations of the bullet-weight, length. surface bearing, meplat, ogive, boattail, base, velocity ect.
Just have him get a good ballistic program and then he can determine his drop/windage. Go further with a Kestrel with AB. He can then see both G-1 & G-7 BC.

 

[Reelamin]

Ya, he's used the system for quite a while and loves it. I told him I could probably make a piece of tape with the drops and windage but he wants the turret. I'm just not sure how to give trued g1 bc and hammers only list estimated g7. Can a guy use one of those lab radar things to get g1?

Find someone with a kestrel and true the trajectory. Never tried exactly what your saying I believe it can be done. Then verify the dope with a ballistic program. Send me the specifics and I'll try for you. For me a pre made turret sucks a lumpy one compared to just dialing the data.

 

[waveslayer]

Bullet manufacture can usually give you the G-1 and G-7. You can't get the BC from a LabRadar. BC comes from many calculations of the bullet-weight, length. surface bearing, meplat, ogive, boattail, base, velocity ect.
Just have him get a good ballistic program and then he can determine his drop/windage. Go further with a Kestrel with AB. He can then see both G-1 & G-7 BC.

There are programs that will calculate BC for you. COLDBORE, GENSIS and even AB I think. Again you're shooting your rifle and writing down DOPE, so skip the turret and just dial your actual data by then.

 

[FEENIX]

Ballistic apps requires either a G1 or G7. Use what is readily available and go from there.