Wannabebwana, it's my understanding that the Ruger used a 1-10" twist. So my guess is that 1-10" IS within established gun manufacturers' norms. Just on the tight side. If the 1-12 will stabilize the 320 and 325 grain bullets I personally would be OK with it, but I am fairly new to the 9.3 bore size and don't have the base of knowledge that some other shooters and gunsmiths may have. MY idea of asking for 1-10" is based on what limited reports I have heard, and also because the Ruger uses it and my #1 is super accurate with everything I have tried so far.