Ruger tang safety or Mark I's, as they are referred to now, have a 1"10" twist in .234 Winchester bore. I have a RSI tang safety in .243 with the 18 1/2" barrel full stock. I consistently shoot 3 shots at 100 meter measured range where a quarter (1") will completely cover the holes and in almost all weather conditions. This is with hand loaded ammo using R-P brass, CCI 200 primers, 42 grains of IMR-4350 powder, and 100 grain Sierra BT or 100 grain Speer flat base bullets. The groups by either of these are identical. Those older tang safety Rugers did shoot good. I much prefer them over the newer models.