Hi and welcome. You will get a ton of answers to this , all different and none of them wrong. Depends how you work and which machines suit you the best. I mainly use my hyper v3 for lining, it's shit at everything else so I have it set up permanently as a liner and it does it very well. My halo will line effortlessly with a 3.8 or 4.2 cam and my HM adjustable DD will bury any grouping at around 8v set at 3.5 - 4mm. Those are just a couple of very capable lining machines. Hope that helped a bit.