5R rifling

groundhog244

Can any body put the answer in simple language. What is 5R rifling. I see that different firearms companies are going to this type of rifling. Thanks .

iceracerx

11b6r

5 lands that have a radiused edge

Hawk Carse

Good pictures.

Not just radiused, there is a distinct slope to the sides of the lands.

As the story goes, barrel maker Boots Obermeyer got an early look at an AK74. The AK74 has four grooves of what the British called "trough shaped rifling" back when other makers were looking for something to compete with Whitworth's hexagonal bore. Nothing new under the sun.
Mr Obermeyer liked the Russian form but thought five grooves would do better than four. Hence 5R for "five grooves, Russian style."

Other barrel makers picked up the type under different names, one term is "canted rifling."

bobski

i shot a boots 10/1 5R on my M21 match rifle. works best with 168gr bthp.

XXCross

Hmmm....not much different than the rifling in a 1917 Enfield.

Hawk Carse

Enfield rifling has square lands and grooves and is deeper than US standard.

nononsense

According to no less an authority than Hatcher's Notebook:

We retained the Enfield form of rifling, but changed the bore and groove dimensions to suit our own bullet diameter of .3086 inch. To accomplish this we changed the bore from .303 inch to .300, and made the grooves .005 inch deep instead of .0058 as in the .303

Hatcher goes on to make the point that with the five-groove rifing there's no placce where groove diameter can be measured directly, but that in an overall sense the Enfield barrels were actually
...somewhat tighter than the rifling we had been using on the M 1903...because after careful tests it seemed to give the best results for that form of rifling with the diameter of bullet we were already using.

Hatcher goes on to say:

This has been gone into at some length because we so often see in print the erroneous statement that the 1917 has a bore that is too loose because we "used the British dimensions" ...

All of the original 1917s were five groove. On refurbishment some were changed to four groove with barrels made by Hi-Standard Manufacturing, and some were changed to 2 groove with the Johnson Automatics barrels.

The Remington Model 30 was a post WWI sporter based on the M17 action - Remington had vast inventory and production capacity for these when WWI ended, so stuck a rather skinny sporter stock on a lightly modified M17 and put them on the market in 1921. They were refined a bit further as time went on, as the Model 30 Express and later 30S and other variants, and the line was finally discontinued about 1941.

charliemeyer007

Some firearms shoot better than others IMHO. Generally the more you spend they better they shoot but not always.

Should I ever get the chance to freshen the bore on my shot out .256 Newton barrel to 7mm, I like to do it in a gain twist with parabolic edges to lands/groves