Can someone please advise me and could you back it up with some math. Specifically I want to rebarrel a 30 year old 30-06 SPRG. with a very good. At present my loads seem to run considerably slower than published data from all the manuals. I just want to kick this idea and question around by some of you learned more
wise scholarly reloaders and possibly gunsmiths or math professors. Thanks for your valued responses in advance.

The short answer is the number of grooves has very little (in any) effect on velocity. There's more info on your question here:

http://www.6mmbr.citymaker.com/barrelFAQ.html#24636

worry less about the grooves and more about lenght. My 22' 06 also runs much slower than published data. You will gain some velocity if you go to a 26" tube.

Even between different barrels of the same length there are variances that result in some barrels being "fast" and others being "slow"

Some claim that fewer lands and grooves disturb the shape of the bullet less and thus make a barrel more accurate.

a slower twist rate will often increase speed a bit.

a longer throat or "leade" (ala' Weatherby) CAN increase velocity, but doesn't always do so...

AD

I've had two 30-06 build one using a Lilja 3 groove 1/11 twist barrel other a Bartlein 1/11 twist 4 groove barrel. Using the same loads with 165gr bullets the Lilja is appr 55fps faster. Both rifles are very accurate and they don't foul same gunsmith build both rifles headspace the same so I fire same ammo in either rifle.

The Bartlein barrel rifle had a Kreiger 1/10 twist barrel in 30-06 was a very accurate rifle but I got a bug up my tail to change things.

Since I've only used a Lilja,Bartlein and Kreiger barrels for the 30-06 the amount of grooves doesn't effect accuracy (been lucky with choice of gunsmith) but I think they effect velocity in a small way.

I use a Lilja 30 cal 3 groove barrel for a 300Wby had a factory 300Wby also used a 30 cal Lilja 3 groove for a 300mag had a Kreiger barrel 300mag.

In my limited experience the Lilja 3 groove 30 cal has been alittle faster when I use the same loads in other brands of barrels.

Another way to increase velocity is get a Broughton 5c barrel in 30 cal
http://www.rifle-barrels.net/bore.html
I've got one on a 300WSM great barrel gave me over 100fps more at less pressure.

Well good luck

If all the "evidence" of correlation between observed velocity and number of lands and grooves is going to be heuristic, I don't think it is worth a hoot.

You have no idea what the dimensions of the chambers, lands and grooves are in the barrels included as "evidence". So any difference in velocity observed might as well have to do with different chamber/land/groove dimensions. I know this is not scientific in any way, but I tend to believe: all things being equal, higher velocity means higher pressure.

I personally think you are barking up the wrong tree, if you are trying to select your barrel maker according to a perceived idea of what the final velocity of your loads are going to be.

Besides, most barrels I have worked with have been "slow" when compared to the data found in manuals. It is exceedingly rare I have observed velocity numbers matching those listed in the manuals. And when I have gotten close to published velocities, it has mostly been at the cost of high pressure (as in: short brass life due to expanded primer pockets). I guess a lot of published data are obtained from barrels with minimal dimensions (chamber, groove etc), just to make sure the data would also be safe in "sloppy" real-life barrels (custom or factory).

Oh, there seems to be one gigantic exception to people not being able to obtain published loads: on the Internet, it seem most (or at least some) shooters are able to exceed published velocities with regularity. But then again, it is rare these days to find guns on the Internet that shoot groups larger than .5"....

- mike

quote:

Rifle barrels: effect of number of lands and grooves to velocity

Zilch.Zero