New!! By request, I recently developed a 243 Winchester SUBSONIC round shooting the 75 grain Sierra HP at 1030 fps in 22″ barrel. This is with new high-end Norma brass and Sierra 75 grain HP bullet. This bullet will stabilize in a 1:11″ twist barrel or faster (1:10″, 1:9″, 1:8″, 1:7″, etc).
Priced per 100 rounds
Why use a 75 grain HP bullet? Most 243 Win barrels will have a 1:10″ twist barrel, with some having a 1:9″ twist or faster. To get a subsonic .243″ bullet to fully stabilize at subsonic speeds in a given twist rate, bullet stability becomes a huge factor for it to stabilize and shoot well. Bullet length is a major factor in how stable a bullet is in a certain twist rate. In a given 243 Win twist rate (like a 1:10″ barrel twist) and slow subsonic speeds, a shorter, flat base bullet is more stable than a longer BTHP match bullet is. The 75 grain Sierra HP flat base is a much shorter bullet than a similar weight BTHP bullet, or a 100+ grain SP or HP bullet. This allows the 75 grain HP flat base to be more stable and have the potential to be more accurate at subsonic speeds than a BTHP design that makes the bullet longer, requiring more twist rate to stabilize it. BC (ballistic coefficient) is for supersonic flight, and does not matter at subsonic speeds. Having a high BC bullet at subsonic does not benefit the shooter at all. This is why the 75 HP flat base bullets work well as subsonic round in the 243 Win!