Re: Building 6mmAI, how long of a barrel?
If you want to use most of the 100-107 gr bullets you will need a 1 in 8 twist. As for length for a 6mmAI I'd opt for 28". I have a 28" 257 weatherby and that barrel added velocity without being too long for me. Get the barrel long, you can always cut some off and recrown if you find it objectionable.