Range Report 6mm twist rate question

[SquarePizza]

Looking to my next barrel and asking a ton of questions...

Currently, I am wondering about twist rate for my 243, which is currently running 85 grain game kings.


According to lilja's website, they recommend a 1:12 twist for 85 grain bullets, 1:10 up to 100, and 1:8 over 100. My question is, what happens to the 85 grain bullets when fired from a 1:10 or 1:8?



*Disclaimer* I am using the 85s because I live in NY and over 550 yards is very rare for me to shoot, therefore I like the 85 SGKs because they are cheap, shoot great out of my current barrel, and seem to do well at the ranges I am using them at. However, I wouldn't mind being able to use the heavier ball in the future if I so want to.

 

[Graham]

6mm twist rate question

My question is, what happens to the 85 grain bullets when fired from a 1:10 or 1:8?

They spin at higher RPM.

Not a problem as long as you are using good bullets.

 

[stranded]

^^^ This. Exception, rough barrel will destroy even a good bullet. I have good luck with 85's thru a 1-8 Lothar. 62gr VG's running 3900fps (magneto) stay in tack to 400+ yds.

 

[damoncali]

You will get slightly bigger groups from a faster twist than a slower twist. The difference is real, but small and usually ignored by the non-benchrest crowd.

 

[Smith97z71]

You will get slightly bigger groups from a faster twist than a slower twist. The difference is real, but small and usually ignored by the non-benchrest crowd.

Bigger groups from a faster twist? I would have thought the opposite, interesting

 

[damoncali]

Think about it in terms of defective bullets (and they all are to on degree or another). They all have some imbalance here or there. The faster you spin an unbalanced object, the more it will wobble. It turns out this leads to bigger groups when you're talking about bullets. That's a pretty big oversimplification, but it's basically what goes on.

This is why match bullets are so expensive - to keep them balanced. And why benchrest rifles are built with slow twists - as slow as 1:20 for a .30BR for example. They try hit hit the ragged edge of stability while spinning as slow as they can get away with.

For long range bullets, this effect is way smaller than the ballistic advantage of heavy bullets, so we put up with the higher twist required to stabilize them. But if you know you only want to shoot light bullets through a barrel, you're better off with a slower twist.

 

[SquarePizza]

Thanks for the responses guys.

I know that I pretty much want to shoot the 85s, but it takes me a few years to burn out a barrel so I wouldn't mind experimenting with a faster twist in case I wanted to try something heavier over the next few years.

 

[Rifle Barrel Blanks]

Benchmark barrels is making some really awesome 6mm barrel. Give them a call and they will get you all squared up

 

[7GRT]

Should work fine , just avoid 100g bullets . IMHO