168gr b.c.

[longrangeshooter1]

Whats the b.c. to the sierra 168 gr matchking .284? Im seeing .488 is that really the b.c.?

 

[Mikecr]

It's ICAO G1BC is .565 avg across velocities.
This, from Applied Ballistics for Long Range Shooting, Pg 446

 

[Michael Courtney]

It's ICAO G1BC is .565 avg across velocities.
This, from Applied Ballistics for Long Range Shooting, Pg 446

This is one of those cases where the Sierra measurement differs by a lot from the Litz measurement. In most cases, Sierra and Litz are within 5% of each other.

In your rifle, the BC could be anywhere in between.

 

[longrangeshooter1]

I was gonna get some for my 7saum until I looked up the b.c., I would of thought it would of least been 550. I will try some with the 565 b.c. and see where that gets me.

 

[Jud96]

So if Sierra's BC is off, then what would the true BC of a .30cal 190gr SMK be?

 

[Michael Courtney]

So if Sierra's BC is off, then what would the true BC of a .30cal 190gr SMK be?

What is this true BC of which you speak?

Sierra's published BCs tend to be the most accurate provided by manufacturers. The 168 grain .284 is unusual because it is so far from what others have measured.

The 190 SMK has a G1BC reported as 0.533 by Sierra and a G1BC reported as 0.542 by Litz. That's less than a 2% difference.

BC can vary depending on what rifle, twist rate, and velocity the bullet is shot at, but if twist rate and velocity are the same, most heavy match quality barrels will be with 5% of the Litz number. Factory barrels, thin barrels, and relatively high or relatively low twist rates can give bigger differences, usually lower BCs.

 

[Jud96]

What is this true BC of which you speak?

Sierra's published BCs tend to be the most accurate provided by manufacturers. The 168 grain .284 is unusual because it is so far from what others have measured.

The 190 SMK has a G1BC reported as 0.533 by Sierra and a G1BC reported as 0.542 by Litz. That's less than a 2% difference.

BC can vary depending on what rifle, twist rate, and velocity the bullet is shot at, but if twist rate and velocity are the same, most heavy match quality barrels will be with 5% of the Litz number. Factory barrels, thin barrels, and relatively high or relatively low twist rates can give bigger differences, usually lower BCs.

Okay I wasn't sure the .533 BC was correct compared to the higher Berger 190gr BC.

 

[BryanLitz]

Sierras reported BC's for all 7mm bullets tend to all be low compared to my measurements by a pretty consistent margin, I think it's like 7 to 9% on average.

Other calibers are closer, and +/- from zero error, but their 7mm BC's are systematically low.

I told them this once and they just said "We know".

-Bryan