First off, I think a 1 in 10 twist rate is fine for all practical shooting. My particular experience is mostly with an off the shelf unmodified Rem 700 varminter purchased around 1977 with a 1 in 10 twist. If I remember correctly the lightest bullet I could find was the 60 gr. Sierra FB. I also used the 70 gr. Sierra HPBT match bullet. Accuracy between those two was slightly better in the 70 gr. I also used the Sierra 85 gr. HPBT. There was very little difference in accuracy.
Some of these targets are at 200 yards.
Now, the rest of the story. When I bought my rifle my shooting partner bought the exact same rifle only in 6 m/m. At the time he believed the 6 m/m had the same twist rate as the older 244 which was 1 in 12. He wanted the slower twist to shoot lighter bullets. What he got was a 1 in 9 twist and the results were a rifle that shot 87 gr. bullets better than 60 or 70. And when I say better, it was noticeably better.
I think that when you get into the competitive shooting game where the goal and necessity is very small groups shot from custom built rifles you are obviously better off with a twist tailored for your specific bullet.
6mm/.243
- 8" Special for VLD bullets over 100 gr.
- 8"* Ratchet rifled 4 groove
- 10" For bullets up to 120 gr. and VLD under 100 gr.
- 12" for bullets up to 85gr.
- 13"* for bullets up to 75gr.
- 13.5"* for bullets up to 70gr.
- 14"* for bullets up to 70gr.
- 14"* Ratchet rifled 4 groove
- 15"* Special for bullets up to 70gr.