what effect does barrel twist have?

[rocknwell]

Hello, can i get some help on understanding how different ratios of barrel twists affect the flight of bullets? does a smaller ratio (faster spinning bullet) go straiter than a larger ratio (slower spinning bullet)? what effect do these have on BCs? I'm looking to get a rifle in either 7mm rem mag or .308 and i'd like to know what type of barrel twists i should be looking for/what not to get. Thank you!

Micah

 

[Coyboy]

Hello, can i get some help on understanding how different ratios of barrel twists affect the flight of bullets? does a smaller ratio (faster spinning bullet) go straiter than a larger ratio (slower spinning bullet)? what effect do these have on BCs? I'm looking to get a rifle in either 7mm rem mag or .308 and i'd like to know what type of barrel twists i should be looking for/what not to get. Thank you!

Micah

the longer/heavier bullets require faster twist rates for the given bore, than the short stubby lighter bullets.

If your getting a factory rifle your choices are pretty slim.

If your getting a custom tube tell your smith what bullets you plan to shoot and he will get the proper twist.

If you need more try the search function or google.

one twist is no more accurate given that the bullet matches the twist.

 

[rscott5028]

I beleive Jim answered your question. He can also build you exactly what you want/need.

But, here's more info.

It's like a nice spiral footbal pass vs a wobbly throw. If you spin it too fast, it doesn't buy you anything while too slow will reduce your accuracy.

Here's a link to some good rule of thumb numbers...
Welcome to Shilen Rifles, Inc.

Sometimes the bullet makers have a recommended twist rate as seen here...
Berger Hunting Bullets

Here's an online tool for calculating the ideal theoretical twist rate...
JBM - Calculations - Stability

Hope this helps.
Richard

 

[rocknwell]

Thanks guys i appreciate it. I will look into it.

 

[roninflag]

for me barrel quality is way more imporatant than twist rate.

 

[MHO]

rscott and coyboy explained it well. It all comes down to stabilizing the bullet which will make you more consistent. Barrel twist will affect it depending on the bullet you are using.

 

[270winshort]

just to add on your question on how it affects bc the bullet has a bc the twist rate does not affect the bc of the bullet, provided you have the proper twist rate for the bullet that you are going to shoot, to fast a twist rate is better than to slow, IMO, so it is better to get a barrel with a slightly faster twist than one slightly slower

 

[rocknwell]

thanks guys i appreciate it. that helps me understand things better.