I was looking at a ballistics program and it asked me what my bullet's "native drag model" is. It went from G1-G7. Does anyone know what a 7mm mag 168 Matchking native drag model is?

quote:

Originally posted by craigcampbell:
I was looking at a ballistics program and it asked me what my bullet's "native drag model" is. It went from G1-G7. Does anyone know what a 7mm mag 168 Matchking native drag model is?

Those are 2 different ways of measuring BC. Go to the bullet mfg. site to get the bc and which method they use.

For the most part, manfactures use the G1 drag model for their BC numbers, simply because it returns a higher value. Sierra's "BC changing with velocity" numbers is due to their using the incorrect Gx for the bullet in question, NOT due to the BC being effected BY the velocity.
The "standard" for a G1 BC is a 1 pound, 1 inch diameter projectile with a flat base3" long with a 2 inch radius tangential nose.

quote:

G1 or Ingalls (by far the most popular)
G2 (Aberdeen J projectile)
G5 (short 7.5° boat-tail, 6.19 calibers long tangent ogive)
G6 (flatbase, 6 calibers long secant ogive)
G7 (long 7.5° boat-tail, 10 calibers tangent ogive, preferred by some manufacturers for very-low-drag bullets[10])
G8 (flatbase, 10 calibers long secant ogive)
GL (blunt lead nose)

Since these standard projectile shapes differ significantly the Gx BC will also differ significantly from the Gy BC for an identical bullet. To illustrate this a bullet manufacturer has published a G1 BC of 0.659 and a G7 BC of 0.337 for their 7 mm Match Target VLD bullet and has since published the G1 and G7 BCs for most of their target bullets.[11] In general the G1 model yields compariatively high BC values and is often used by the sporting ammunition industry.

From http://en.wikipedia.org/wiki/Ballistic_coefficient

quote:

Originally posted by craigcampbell:
I was looking at a ballistics program and it asked me what my bullet's "native drag model" is. It went from G1-G7. Does anyone know what a 7mm mag 168 Matchking native drag model is?

Usually when I hear that asked, I think in terms of the "Rupaul" of Aboriginal origin...

To find the actual BC of a bullet uses the speed at two different distances. You will need a cromo and 12 rounds for the gun that you are useing. The rounds need to be loaded as close as possible, bullets and powder within a 1/10gr. Firer 6rds at the cromo at the bench and throw out the low and highest and adjust the average of the other four to muzzel speed. Then set up the cromo at 100 yrds(200 would be better) and do the same thing to find the average of the middle four rds. Almost any balistic program will let you find speed at a distance if you have the muzzel speed and BC of the bullet. Enter the muzzel speed and bullet makers BC number and check what the down range should be and if it is not the same as your down range speed adjust the BC number up and donw till it is you down range fps and that is the true BC for that bullet in your gun.

My program lets you calculate BC from actual bullet drop.

BulletFlight

quote:

Originally posted by rcamuglia:


Usually when I hear that asked, I think in terms of the "Rupaul" of Aboriginal origin...

I had that same terrible picture flash through my mind for a second there too.

I was hoping someone would "get" it!