1:10" is a good twist rate for most rifles. As noted below, championships have been won with 243 using faster twists and even heavier bullets.
The answer to your question is best answered with Stability Calculator. Follow this link,
http://jbmballistics.com/ballistics/.../lengths.shtml
note your bullet length, then click on the
calculators in the upper left corner. Then select Stability at the bottom.
"Stability
The Miller stability value. It should be between 1.3 and 2.0 to ensure stability (the military uses 1.5)." I read somewhere else that 1.4 was good (stable) Higher is more stable
The Sierra 100.0 grn SBT (a hunting bullet) gave these Marginal results at 2800 fps:
Cal¡ber:
Bullet Length:
Munie Velocity:
Temperature:
Stability:
Stability
Input Data
0.243 in Bullet Weight:
1.078 in Plastic Tip Length:
2800.0 ft/s Barrel Twist:
59.0 °F Pressure:
Output Data
100.0 gr
0.000 in
10.0 in
29.92 in Hg
Stability: 1.346 Marginal
While the same weight but slightly slower flat base give Excellent results:
Stability
Input Data
Caliber: 0.243 in Bullet Weight: 100.0 gr
Bullet Length: 1.041 in Plastic Tip Length: 0.000 in
Muzzle Velocity: 2600.0 ttls Barrel Twist: 10.0 in
Temperature: 59.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 1.469 Excellent
My recommendation is that you try the Sierra #1540 100 gr flat base and see how they work in your rifle. I think they will be stable and shoot well (not spray all over or keyhole).
OHeir wrote:
Quote:
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Mind you, a .243 shouldn't have a 1 in 10 twist
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This statement is untrue, as well as not supported ANY facts.
I also have no idea what he means. Does he opine that 1:10" is too slow? Or too fast? 1:10" is fairly midstream as rifle twists go. You need faster twists with longer and heavier bullets. 1:12 would be typical for Varmint rifles with light bullets.
Sierra used a 1:9.125" twist barrel for their load data, while recommending 1:8 or 1:7" twist for Sierra 107 grain HPBT MatchKing. Savage and Remington sell rifles with 1:9.125" twist.
http://www.accurateshooter.com/cartridge-guides/243win/
"In 1993, G. David Tubb used the 243 to win both the Highpower Championships at Camp Perry, Ohio, and the National Silhouette Championships (both heavy and hunting rifle), at Raton, New Mexico. The Sierra 107 grain HPBT MatchKing that David used in these matches requires a fast-twist barrel to properly stabilize. We recommend this bullet be used in a 1x7” or 1x8” twist for optimum results."
Howa's 243 has a 1:10 twist.
http://www.howarifles.eu/resources/HOWA.pdf
It is impossible to determine where OHeir gets his mis-information, or why, since he makes statements of opinions, as if they were facts, with ZERO factual support. And very often, as here, they are useless, un-supported, potentially misleading, and
obviously wrong.