9 twist works just fine for the Berger 180's.
Guys you have to keep in mind if this is a hunting rifle... what temps are you hunting in? If you chronograph your ammo prior to your hunt and the temp is 70 degrees out but then you go hunting and it's down in the 20's.... expect a velocity loss.
Velocity plays a part when it comes to stabilizing a bullet. Bullet length and twist are more critical but velocity can play a part.
I've shot 8.5 twist and 9 twist on 7mm match guns and hunting rifles. Pick your poison for the most part.
A faster twist doesn't hurt you as much as some think it will. The key is shooting a good quality bullet and ammo that doesn't have a lot of runout in it. Ammo with a lot of runout and or shooting a poorer quality bullet... that's when you possibly start to see accuracy issues.
Also keep in mind for the 9 twist.... button rifled barrels the twist isn't always uniform in them and or can start out at 9 but end up slower.
According to my twist calc's the Berger 180 VLD's at 2800fps need a min. twist of 8.8. My first match gun I built I did a 8.5 twist. 280AI. Shot like a million bucks. The older Sierra 168's shot like a million bucks as well and those for sure would fly in a 9 or even a slightly slower twist. I ran the 180's at an honest 2800fps.
At 2600fps.... the 180 VLD will need a 8.37 twist. At 3000fps they need a 9.23 twist.
So there is your example of how velocity does play a small part in stabilizing the bullet.
Later, Frank
Bartlein Barrels
Guys you have to keep in mind if this is a hunting rifle... what temps are you hunting in? If you chronograph your ammo prior to your hunt and the temp is 70 degrees out but then you go hunting and it's down in the 20's.... expect a velocity loss.
Velocity plays a part when it comes to stabilizing a bullet. Bullet length and twist are more critical but velocity can play a part.
I've shot 8.5 twist and 9 twist on 7mm match guns and hunting rifles. Pick your poison for the most part.
A faster twist doesn't hurt you as much as some think it will. The key is shooting a good quality bullet and ammo that doesn't have a lot of runout in it. Ammo with a lot of runout and or shooting a poorer quality bullet... that's when you possibly start to see accuracy issues.
Also keep in mind for the 9 twist.... button rifled barrels the twist isn't always uniform in them and or can start out at 9 but end up slower.
According to my twist calc's the Berger 180 VLD's at 2800fps need a min. twist of 8.8. My first match gun I built I did a 8.5 twist. 280AI. Shot like a million bucks. The older Sierra 168's shot like a million bucks as well and those for sure would fly in a 9 or even a slightly slower twist. I ran the 180's at an honest 2800fps.
At 2600fps.... the 180 VLD will need a 8.37 twist. At 3000fps they need a 9.23 twist.
So there is your example of how velocity does play a small part in stabilizing the bullet.
Later, Frank
Bartlein Barrels
