Where the back side of the land meets the groove it is dished out instead of meeting at a 90 degree angle. I had a picture but threw it away in a fit of housecleaning last year. Shit, I just remembered! There was an article obout Boots Obermeyer and his rifling in a back issue of Precision Shooting . I will dig it out this weekend. Send me a pm with your address and I'll mail you a copy.
JCN

Marc,

The junction of the lands and the grooves in a 5R barrel are not at a square 90 degree angle rather, they have a radius or a transitional type angle between the land and the groove. Idea is to reduce bullet jacket stress and gain a better bore seal with less gas leakage. I am not sure if this radius is on the driving or the non-driving side of the lands, or both. 5R is also quicker and easier to clean as the copper has not been forced into the 90 degree "corner" between the land and groove. There also *might* be some what less stress on the side of the land itself which *could* result in longer barrel life...?

Aside from the above advantages I have also heard 5R barrels tend to be a bit faster than those with traditional rifling.

Regards,
Dave

First off...all 3 makers (Obermeyer, Border Barrels, and Mike Rock) turn out excellent barrels.



The Russians apparently must like it too, as that is reportedly from whence Boots adopted/adapted it.



Incidentally, Mike Rock and John Krieger reportedly both learned the barrel-making trade at least partially as students (employees) of "Boots" Obermeyer. I have heard, but CANNOT confirm, that there was an agreement by the two students that they would not make 5-R barrels in competition with Boots during his lifetime. I have also heard it said that agreement is why John Krieger does not offer 5-R barrels as well. I CAN'T confirm that tidbit either.



I talked with Mike Rock about that 4 or 5 years ago, and he explained to me why he feels he can make 5-R barrels without violating any such agreement, but darned if my feeble old brain cells can recall the gist of it. Did sound somewhat reasonable at the time though....



Mike also told me (in 2002) many of his .30 barrels, in the 1 turn-in-11.28" twist, were being used in Afghanistan by some of our super elite force snipers, with remarkable success at "extended" ranges.



I have four of Mike's 5-R .30 1-11.28 barrels and they are all outstanding pieces of work. They also apparently sell well at Camp Perry each year, too. I have one local friend who is a "Distinguished Marksman" that buys a couple (or more) from Mike every year when he (Ralph) goes back there to shoot the Nationals. I have heard no complaints of any sort from him about Mike's 5-R barrels, and like all higher level competitors, he has strong opinions about what works and what does not.



Alberta Canuck

What can you tell me about the 5R/7R rifling used in the cut rifle barrels produced by Obermyer, Border Barrels and Mike Rock?



From what I have seen 5R is used quite alot by the bench rest crowd and is often claimed to increase velocity as well as making the barrel a good deal easier to clean.



Thoughts or experience with 5R barrels? Any other positives or negatives associated with this type of rifling?



Regards,

Dave

Alberta Canuck,

Have you heard anything about the ABS barrels that use a Rock inner barrel with a graphite wrap for better heat dissipation? I'm thinking of using one to build up an M-4 upper for one of my kids to take back to Afghanistan on his next deployment.

Thanks,

JCN

fwiw,
Of the custom rifles I've had built I am flat out amazed by my Rock Creek 5Rs. As a matter of fact I'm going to have him make one for an upcoming M70 in .375 H&H project. I've used button barrels from Hart, Douglas, Pac-Nor, and Walther LW-50. None of them cleaned up as quickly as my Single Point Cut Rifled Rock Barrels(I own three).

Regards, Matt.

What shape is 5R rifling? I have been unable to find a picture of it or even a description.