Ordering a new 6.8 barrel from ARP, and was wondering what real world differences there are between the two options? 3R is in stock, 5R isn't so there would be a wait for it. Just want a good accurate barrel, no special purposes intended for it.

Thx

3R rifling only has 3 rifling grooves, compared to the normal 4 or 5 grooves. The rifling is slightly larger/wider than the traditional 4 or 5R rifling, but overall has less bearing surface. The 3R rifling offers higher velocities than your traditional 4 or 5 groove rifled barrels. The negative is they generally burn up much faster. The barrel life is not near as long. But if you want more velocity, the 3R will give that to you. Try it!

Thanks Chad,

The rifle is for my kid to hunt with, so barrel life is not much of a concern as long as it doesn't burn out in less than a few thousand rounds. I doubt velocity gains are monumental, but having a few extra fps on a 6.8 couldn't hurt, right?

I didn’t know 3R was a thing. Sounds interesting. Didn’t they produce the old 03A3 with something similar.

About 5-10 years ago the 3R rifling was popular. I almost went with a custom .277" barrel (too good a deal to pass up) for a 270 Win to gain that extra speed. But I decided against it. You will gain some speed. And some shooters I know swear by them.

I believe some of the rifles made during WW2 used a form of abbreviated rifling that was less labor intensive. Like most war time expediences, the goal was "good enough", not good.

I've was given the option of 3R with some of the custom barrels I've ordered in the past. Never went with it. Supposedly higher velocities, as mentioned already.

I've got over 5,000rds through my 6.8 16in 3r barrel from AR performance. Just developed a new load that shoots right at an inch at 100 yards. I'm loading 29.2 grains of Accurate 2200, CCI 450, Federal cases, Speer 90 grain gold dots. Getting 2650 fps with a Sandman S suppressor. Kill plenty of pigs with it. The right bullet weighted 72.5 gr and the left 83gr.

6.8 SPC is going to have a pretty long barrel.

Just get it

I ordered the 18" barrel, and those 90gr gold dots will be the first thing it gets fed. Nice to see some real world results on them as well.

The Springfield 03’ had a 2 grove barrel originally, they shoot pretty good too.
Lots of benchrest guys use 4 groove barrels they believe that the less you deform a bullet the more consistent it is.

I tend to agree.

That said I do have all kinds of barrels and they all shoot pretty well.

I've got a AR performance 6.8 16 inch 5r barrel I'll shoot the same rounds through to see the fps difference between the 3r and 5r barrels.

I have one. It’s a Smith-Corona made in 1942 and has the 2 groove barrel. I have placed in Vintage Military matches with it and last week took it with me deer hunting. I shot 2 does and a hog all around 100 or so yards with original peep sights.
Looking down the barrel seeing the two grooves is pretty wild but it shoots from 130gr to 175gr bullets as good as I can shoot with old eyes combined with irons.

Are the lands of the rifling on 3R also radiused as the 5R is?