The Cooper 280AI rifles have a 1 in 10" twist instead of the usual 1 in 9" or 1 in 9-1/2" twists used in most higher velocity 7mm class cartridges.That is just one more think that I liked about the Cooper.I had all of my custom 7mmstw rifles equipped with 1 in 10" twist barrels.
Yeah I seen that twist rate is 1-10! His Gaillard on his 280 AI is a 1-10. Now we did spend more time with the heavier bullets because they seemed to shoot good right out of the gate. That is not to say that with a little work the 139's couldn't shoot too! We found H4350 to be the best powder, with Winchester LR primers. What are your plans for powder primer combo?


















































