Re: Optimal Number of Rifling Lands?
Most factory rifles come in 6 groove regardless of caliber. THere are some exceptions, but generally all are 6.
In custom barrels, nothing is really "normal" anymore. 2,3,4,5,6,8, grooves are all in use.
6's and 8's are absolutely easier on bullets, especially once the throat gets rough. 3's and 5's are common because people believe the fatter land resists forward throat erosion better. While this may be true, in my experience on two different barrels, I found that although my seating depth didn't change to chase the throat during erosion, it still cracked and got rough to the point where it started blowing up bullets or taking forever to clean because of the roughness. So in my opinion, 3 groove work as advertised, but don't begin to think that they resist all kinds of erosion.
I believe the best number of grooves is found somewhere in the middle. I am really liking the idea of 5 grooves as it never puts lands on opposite sides of the bullet so the "pinch" is less. But then again, I have an 8 groove 8 twist barrel that shoots bullets into the RPM level that disintegrates match bullets usually, but because it is an 8 groove, I can shoot 75 grain amax through it at 3450 with no blowups! If it was a 3 groove, the bullets wouldn't even make it through the chronograph in one piece!
Stability comes from the twist, not necessarily from the groove number.
If it's not far, it's boring.