S&W unconventional rifling

[Walt]

I have a Smith model 686 as well as a 696 that both have rifling that is not cut square at the edges. Rather, there's a tiny step at the edges on both. I have examined other 686s that have conventional rifling. Does anyone know whether the current models are still made this way or was the stepped rifling a design that went away?

[Pat C]

I believe that is ECM rifling

[Bronco]

I think it is call 5R rifling! Boots obermeyer was the first to use it!

Obermeyer
True 5R® rifling is an official registered trademark of Boots Obermeyer of Obermeyer Barrels. Krieger Barrels has express permission to use both his "5R" terminology and the groove geometry he developed to produce our 5R® barrels.

[JRD]

That’s ECR (electrochemical rifling). Used by S&W on the majority of revolvers made between the late 90’s and approx 2018. The grooves were literally burned into the bore via an EDM (electrical discharge machining) process using an electrode in the shape of the grooves.
A byproduct of that process is that the lands do not have sharp edges like traditional broached rifling. Don’t worry about the lack of sharp edges.
Other rifling profiles such as 5R (as used by T/C recently) and polygonal also don’t have sharp edges and shoot just fine.
The bores were honed, and with the grooves burned in there should be no tool marks in it. Assuming its crown is undamaged and concentric, that should be a good shooting barrel.

[marlinman93]

I think it is call 5R rifling! Boots obermeyer was the first to use it!

Obermeyer
True 5R® rifling is an official registered trademark of Boots Obermeyer of Obermeyer Barrels. Krieger Barrels has express permission to use both his "5R" terminology and the groove geometry he developed to produce our 5R® barrels.

Boots simply copied what barrel makers like HM Pope and George C Schoyen had done back in the late 1800's, so he sure wasn't first! The way both Pope and Schoyen made their cutters with rounded inside corners so that lead and fouling didn't build up in squared corners like most factory barrels were was new back when both men did it 130 years ago.

[EG73]

That’s ECR (electrochemical rifling). Used by S&W on the majority of revolvers made between the late 90’s and approx 2018. The grooves were literally burned into the bore via an EDM (electrical discharge machining) process using an electrode in the shape of the grooves.
A byproduct of that process is that the lands do not have sharp edges like traditional broached rifling. Don’t worry about the lack of sharp edges.
Other rifling profiles such as 5R (as used by T/C recently) and polygonal also don’t have sharp edges and shoot just fine.
The bores were honed, and with the grooves burned in there should be no tool marks in it. Assuming its crown is undamaged and concentric, that should be a good shooting barrel.

Just look at Lancasters Oval Bore rifling. High end double rifles it was used in.

[Nicknack]

My 308 CZ 550 Ebony Edition has this type of rifling and four grove land and groove. My CZ has a hammer forged barrel. as you can see by the outside of the barrel.

[1894cfan]

Faxon also makes 5R barrels for their match grade ones. I've got an 18" gunner profile match barrel for my AR in 223 wylde.