I have read alot about rate of twist in barrels for different calibers but haven't seen much on number of grooves. I just ordered a new barrel for a Post 64 Model 70 in 6.5x55 with 3 grooves.

What is your preference and why?

Thanks

At the risk of starting a big debate...I have never read or heard any independant credible evidence that shows that a certain number of lands and grooves is superior to another.

I have several barrels in the same caliber (.30) with different numbers of lands/grooves and I have yet to see any difference in accuracy, fouling, ease of cleaning, or wear.

I rebarreled on old Springfield sporter that had the stock military barrel on it. The original barrel was a four-groove and was shot smooth. I got a new in the wrapper Remington military 2-groove to replace it. I wanted the same contour so the stock fit the same. The new 2-groove will print clover leaf patterns at 100 yards.

The gun is old and amazing.

I've been shooting a Lilja 3 groove 17 twist 30 cal. bbl. on my Varmint Hunter class rifle for 2 years. It's chambered in 30 BR and I honestly believe it is the most accurate bbl. I've ever owned.

One theory I have heard is that fewer lands leads to less bullet distortion making the projectile more accurate and gives it a higher BC. The other arguement is that more lands gives the bullet a better seal against the force of the gas. This is Marlin's arguement for their Micro-Groove rifleing, which is actually designed for lead bullets though, so I don't know if it is applicable.

Both theories make sense, but I know Palma shooters typically go with 3 or 4 lands and tighter land and groove diameters. This would prove both theories

Fewer lands may possibly produce higher velocities.

I have 4 groove Krieger’s, 6 groove Schneider’s, and 8 groove Shilin’s...and if there is a difference in the way they shoot I sure haven’t noticed it.

This paragraph is on both the Lilja and the 6mmBr.com websites, with the difference that Lilja says 6 BR is going to test for accuracy vs number of grooves, but no test results are available...jim

What Is the Best Number of Grooves?
Barrel-makers report that, as long as the ratio of lands to grooves is relatively constant, there is no demonstrable difference in accuracy among 3-,4-,5-,6- and 8-groove barrel designs. Krieger has told us "There isn't any advantage to the shooter. Assuming the ratio of the surface area is kept the same, the number of grooves should not have any effect. Barrel makers use different numbers of grooves for ease of manufacturing and ... marketing hype." That said, in our experience, 8-groove barrels are a little slower, and may foul a bit more quickly because there are more edges to cut into the bullet's jacket and to trap powder residue. We see no reason not to specify a 4-groove barrel if that is your preference. Moreover, IBS Hunter Champion Al Nyhus and others have had great success with Lilja 3-groove barrels. Al believes the 3-groove design cleans up more quickly and yields a bit more velocity. Famed gunsmith and wildcatter P.O. Ackley believed that, all things considered, a properly-made 3-groove barrel is optimal for most common calibers. Ackley believed 3-groove profiles can deliver higher velocities with less fouling and no significant reduction in accuracy. In the months ahead, 6mmBR.com plans to do a comparison test of various barrel formats.

The only new opinion on this that I've considered lately is that an odd number of groove compresses the bullet less because lands are not directly across from each other and may be easier on the bullet as it goes down the bore.

I figure that with lands directly across from each other a .308 caliber bore would be .300 in diameter at the top of the lands. With an odd number the bore would be .304.

quote:

Originally posted by Fjold:
The only new opinion on this that I've considered lately is that an odd number of groove compresses the bullet less because lands are not directly across from each other and may be easier on the bullet as it goes down the bore.

I figure that with lands directly across from each other a .308 caliber bore would be .300 in diameter at the top of the lands. With an odd number the bore would be .304.

That would pretty much depend on how deep the grooves were cut...wouldn’t it?

Years ago, the NRA did a credible amount of research regarding the number of grooves and the performance of cast bullets. There was a difference in the design of the cast bullet that performed best in certain barrels, varying with the number of grooves. The results are published in their old cast bullet manual.

That is the only credible evidence that I have ever seen. There is no comparable research for jacketed bullets of which I am aware.

It's more difficult to measure the bore and groove diameters with an odd number of lands and grooves.

quote:

Originally posted by Rick 0311:

quote:

Originally posted by Fjold:
The only new opinion on this that I've considered lately is that an odd number of groove compresses the bullet less because lands are not directly across from each other and may be easier on the bullet as it goes down the bore.

I figure that with lands directly across from each other a .308 caliber bore would be .300 in diameter at the top of the lands. With an odd number the bore would be .304.

That would pretty much depend on how deep the grooves were cut...wouldn’t it?

Most 30 cals are .308 groove depth and .300 on top of the lands, which means the groove depth is .04 on each side.

The grooves would not need to be as deep if the number of grooves is larger.


But more grooves is more Copper fouling.

17 cal varmint hunters buy 3 groove barrels from Pac Nor.

The reason I now go with three-groove barrels on my hot-rods is that they seem to erode a little less fast. More "meat" to each land, takes a longer time to burn up.

The reduced fouling is something I haven't seen, but then again, it's hard to evaluate "fouling" between match barrels. Especially when one is used to factory barrels.... JMO, Dutch.