Can someone explain what 5R means?

[He Shoot Me]

I want to turn my Rem 300wsm varmint into a 7wsm and have been looking at some barrel's. I noticed GAP uses Bartlein in a lot of their builds. So I hopped on their (Bartlein's) website and was looking at the different options.

They offer 4 or 5R for the # of twist rate and was wondering what that was and which would you recommend?

The game plan is to start reloading down the road using 180grn VLD's

Thanks,

-Pat

 

[sobrbiker883]

Re: Can someone explain what 5R means?

Boots Obermeyer was the first in US to cut 5R barrels. Has to do with the shape of the lands and grooves (more so where the land meets the groove).

"Borrowed" from Obermeyer's FAQ:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What does it mean when a barrel is said to be a "5R"?

5R is the form of rifling I developed for use in most target barrels and in many sporting barrels.
These barrels have 5 grooves, and the lands have angular sides. I have observed that bullet jackets
will deform such that they remain closer to the R-form lands than they will to the sharp-edged
lands present in conventional-style rifling. This reduces powder fouling at the corners of the
grooves. The angled form of the lands also helps to reduce jacket failures in quick-twist barrels.</div></div>

 

[SpotcheckBilly]

Re: Can someone explain what 5R means?

In 5R rifling 5 stands for the number of grooves and R stands for Russian, which is a rifling design that Boots Obermeyer studied when he was contracted (by the US Military) to report on the then new Russian 5.45x39 AK74 rifle and cartridge. Boots introduced this rifling form to the US shooter. The corners of the lands are not square like conventional rifling, but are more angular, rounded off, or radiused, if you will. I have three custom barrels that feature 5R rifling, a Bartlein, a Border, and an Obermeyer. I've found that 5R rifling cleans up a bit quicker than conventional rifling. Frank Green agrees.

I prefer 5-groove to 4- groove rifling, if only because with an odd number of grooves no two grooves are exactly opposite each other in the bore. This is thought (theoretically) to be stronger because of wall thickness, but I've no way to prove it

 

[He Shoot Me]

Re: Can someone explain what 5R means?

Excellent!

Thanks you guys. 5R it is!

-Pat

 

[Metalhead0483]

Re: Can someone explain what 5R means?

Google is your friend