Just to add to this post, I have used everything from 2 grove to 8 grove barrels and different types of land designs for the different builds and found that the quality of the rifling and bore, made the most difference in accuracy. The different land designs have a place, depending on what you use it for and the number of lands also have their place depending on the bullets used. Chose the right number and design and if the quality is good you have a winner.
In theory, The odd number of lands should promote centering of the bullet upon engraving. This was once true in most cases when precision bullets, reamers, cartridge cases and general workmanship wasn't as good as it is today. Now, with precision of all components being much better there is no advantage one way or the other. This is where the quality comes in. The only grove count that I felt was/could be a detriment to accuracy was the 2 grove. all others worked fine if the quality was there.
Here is my assessment of preferred grove design and number based on my experience with each of them.
3 grove = Best for small fast calibers for velocity and durability.
4 grove = best for Gas operated rifles where a gas port has to be placed in the
center of the port so it can be placed in the center of the grove to stay away from the lands.
5 grove = best used in mid calibers where bullets are not extremely heavy for the velocity, The have a better chance of engraving well because the number of lands.
The angle of the 5 R lands make it less likely to foul, but with heavy bullets the possibility of less than perfect engraving is greater.
6 Grove = good all round performance and dependability, for large magnums using heavy bullets at high velocity's.
7 Grove = when you can find one, it doesn't offer any advantage over the 6 or 8 grove and is very expensive. It is also thought to be better like the 3 and 5 grove barrels but this has yet to be proven.
8 grove = is normally considered best for very large calibers with heavy projectiles that are hard to start rotating because of their weight. (350 to 600 grains) and get good clean engraving.
There may be exceptions to this, but when building an accurate rifle I have found this to be a good guide and good results 100 % of the time.
My 5 most accurate rifles hunting rifles will shoot under 1/10th MOA and wear 3 grove, 4 grove, 6 grove and 8 grove barrels. The worst shooting premium barrel
i have ever seen/had has been a 5 r and I contribute this to quality control at the factory not the land count.
This is just my experience with different designs and groove count rifling. And what I recommend to my friends that want to build a rifle.
J E CUSTOM