Twist Rate and Max Bullet Weight: Impact Accuracy?

[pcweidman]

Guys I was discussing my new build with a few guys and twist rate and bullet weight came up. I'm sure this has been discussed on here but I do have problems with the search engine on here. Little help if you like...

I have an M40 profile 20 inch barrel with a 1:11 twist on a rifle I am building. My school of thought based on experience and/or take always from Applied Ballistics is that more than around 168gr projectiles out of that rifle wouldn't give me the best accuracy. Given its a friendly competition gun, a hunting rifle, and just a nice fun tool; so I understand I'm not talking about a bench rest gun here. However should I expect less gyroscopic stability from a shorter slower twist rifle compared to a longer barreled faster twist rifle? Should I not push 175's, 180's and such through this gun and expect it to give me the same acceptable accuracy I will expect out of my Match 168's? Or.... Should I expect better?

In addition I do understand some rifles like some loads better and different powder loads equating to a lower Fps or higher Fps could impact the load accuracy. Thoughts?

 

[buffybuster]

Anything between a 1-12 thru 1-10 will work perfectly in your application. There is greater concern of under stablizing versus over stabilizing but within the 10-12 twist range will shoot very well with all bullet weights up to ~190grs with your shorter barrel. I've shot 208AMAX's from a 26" 12-twist (2500fps) and it shot lights out all the way out to 1Kyds.

 

[jdmartin]

I think you will be fine shooting 175-180 class bullets in an 11 twist.

 

[Qld4390]

175's will run fine out of a factory 1:12, so out of a 1:11 it won't be a problem. Unless you're planning on going with a 200gr or heavier bullet, 1:11 will work. The twist rate is not the most important factor when it comes to accuracy. A good quality barrel will give you good accuracy when installed by a competent gunsmith.