LRH Team Member
- Feb 14, 2021
- North Carolina
I was under the assumption "R" meant radiused rifling, same, w/o the sharpness of the edges of the rifling.Not that can be reasonably measured. The 5R benefit is how the rifling engages the bullet opposite the grooves. The bullet is thought to be better supported traveling down the barrel.
5R is a 5-groove rifling pattern with sloped or angled sides to the lands. All rifling has a certain amount of angle to the sides of the lands as a natural effect of the rifling process. The sides of the grooves are parallel, but the sides of the lands are not and the 5R carries this to an extreme.
So why should this be good? It is felt the 5R may seal off the bullet better. Also, the angle of the lands may be less stressful to the bullet jacket, so thin-jacketed match bullets would be less likely to come apart at the high spin rates longer bullets require. It is also felt to be easier to clean as there are no tight corners next to the lands to hold powder fouling.
The 5-groove type of rifling comes from the belief an odd number of grooves is also less stressful to the bullet because it doesn’t have two lands directly across from one another.
Interesting, I have only shot 1 5R barrel, nothing stood out IMO, other than I do not recall a break in. Barrel did not speed up up, ever, but the same occurred with a 3 groove Mullerworks 6.5 barrel.Regular cut barrel is 6 groove so what you would need to do is have a 5R barrel of exact same dimensions to compare identical load performance. I just like knowing my bullet is not being compressed immediately opposite forces.