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J. Valentine
04-24-2011, 01:48 AM
Is a .001 pressure ring on a flat base bullet classed as a driving band for the purpose of calculating BC data ?
Or is it of no consequence to actual external ballistic trajectory after the bullet has gone down the barrel and been engraved and expanded to the bore ?

R.G. Robinett
04-24-2011, 10:27 AM
Is a .001 pressure ring on a flat base bullet classed as a driving band for the purpose of calculating BC data ?
Or is it of no consequence to actual external ballistic trajectory after the bullet has gone down the barrel and been engraved and expanded to the bore ?

No & Yes.

J. Valentine
04-24-2011, 09:39 PM
Thanks Randy . Could you answer another question please. How do I go about measuring and calculating an Rt / R head shape for an ogive on my bulllet ?

R.G. Robinett
04-30-2011, 09:42 AM
Thanks Randy . Could you answer another question please. How do I go about measuring and calculating an Rt / R head shape for an ogive on my bulllet ?

Joe,I haven't a clue.:confused::(RG

GerryM
04-30-2011, 09:49 AM
Are you asking Radis tanget to Radis? If so the die makers have an idea. They also have charts with given ogives.
Hatchers note book had a chart with ogive shapes also explainations how different ogives performed.

J. Valentine
04-30-2011, 10:43 PM
Are you asking Radis tanget to Radis? If so the die makers have an idea. They also have charts with given ogives.
Hatchers note book had a chart with ogive shapes also explainations how different ogives performed.
Thanks for the reply . Yes I am trying to work out how to physicaly measure Radius Tangent to actual measured radius. Rt / R . I have got another thread going on this and some good info has come out . I had some of my data screwed up . My problem is that a point forming die may well say 8 caliber ogive and they may sell it as an 8 cal Tangent ogive but how do I know I am getting a perfect 8 cal Tangent ? When I place my 224 tangent and 6mm tangent bullets beside my 308 tangent bullet . The 308 don't look tangent to me by eye anyway .

J. Valentine
04-30-2011, 10:46 PM
Joe,I haven't a clue.:confused::(RG

Thanks anyway Randy . I have another thread going and "mturner" has cleared up some mistakes I have made and offered an interesting solution., similar to what Bryan Litz says he does.

GerryM
04-30-2011, 11:02 PM
The chart i was speaking of in hatchers note book has several Ogives in several calibers.
All you have to do in lay the bullet on the chart and match up. It should be very close.
You will get a good look at what you have. If te lines don't match up your probably in between
Lets say for IE you think you have an 8 og and it falls short. It's not a 7 Og by the chart but not an 8 og either
Lets say It's in the middle. That leave a 7 1/2 ogive. It pretty easy.
At least you can get a feel for what you have. Then you can do some math if you want to.

J. Valentine
05-01-2011, 04:14 AM
The chart i was speaking of in hatchers note book has several Ogives in several calibers.
All you have to do in lay the bullet on the chart and match up. It should be very close.
You will get a good look at what you have. If te lines don't match up your probably in between
Lets say for IE you think you have an 8 og and it falls short. It's not a 7 Og by the chart but not an 8 og either
Lets say It's in the middle. That leave a 7 1/2 ogive. It pretty easy.
At least you can get a feel for what you have. Then you can do some math if you want to.
I know what you are saying . My problem is slightly different . I need to know how much an Ogive is secant or not when infact they are saying it's Tangent . There is a ratio to describe this and it's the Rt /R ratio . I have used ogive charts but they are not precise enough for this problem .