.223 - 69 gr. Bullets in 1:9 Twist

[Jim22]

In the .223 cartridge guide at this forum,

http://www.accurateshooter.com/cartridge-guides/223rem/

it says the maximum weight bullet for a 1:9 twist barrel is a 73 grain BT. I have been shooting 69 gr. Sierra match bullets and getting very nice results... under 1/2 MOA My question is this: At what range does this bullet lose enough velocity, or at what velocity does this bullet become unstable from the 1:9 barrel? It seems that the 69 grain Sierra is pushing the limit of stability. However, at longer ranges the bullet should slow enough to give up the accuracy it has at shorter ranges.

 

[liseo]

I've used Sierra 77 grains in my 1/9 tw with good results at 300 m.


But believe is on the edge

 

[boltman223]

In the .223 cartridge guide at this forum,

http://www.accurateshooter.com/cartridge-guides/223rem/

it says the maximum weight bullet for a 1:9 twist barrel is a 73 grain BT. I have been shooting 69 gr. Sierra match bullets and getting very nice results... under 1/2 MOA My question is this: At what range does this bullet lose enough velocity, or at what velocity does this bullet become unstable from the 1:9 barrel?

I think about 1493.8 fps so I'd say about 598 yds. Give or take half a yard. I'm pretty sure that's why I get those 8's

 

[Taildrag15X]

I pushed factory Federal Match 77gr and 80gr out of my Savage 112BT 1-9" twist barrel with good results at 300, 500 and 600 yards.

I've had other 1-9" twist rifles that I worked hard to get 69gr Sierra's to group let alone compete with.....

 

[Bryan Litz Ballistics]

Bullet weight is just one element that determines stability from a given twist; length matters a lot too.

To answer your question, it depends a lot on altitude and conditions as to the range the bullet will slow to a critical speed where stability becomes an issue. At sea level, my guess is you're good to 600 or so. At altitudes of 5000+ feet, you may reach 800 or more. Go high enough and the bullet will retain enough velocity and not see instability even at 1000 yards.

Here's a tool you can use to determine twist requirements for any bullet:
http://www.bergerbullets.com/twist-rate-calculator/

Take care,
-Bryan

 

[Jim22]

Thank you.