Some barrels have an 8 groove bore,some have 6 and some I believe have less.It seems to me that the more grooves the barrel has,the slower the twist rate.

Has this got something to do with an increase in chamber pressure due to more friction on the projectile when the lands bite?

Is there a better explination?

Thanks.

I wouldn't get bent out of shape about it.
I've known 2-groove 03A3 barrels to shoot great, as well as Marlin Micro-groove barrels to shoot great too.

That pretty much runs the spectrum for number of grooves.

-Spencer

quote:

Originally posted by mix3006:
Some barrels have an 8 groove bore,some have 6 and some I believe have less.It seems to me that the more grooves the barrel has,the slower the twist rate.

Has this got something to do with an increase in chamber pressure due to more friction on the projectile when the lands bite?

Is there a better explination?

Thanks.

mix,

The twist rate is a representaion of what distance it takes the projectile to make one revolution in the barrel. The lands and grooves cause the bullet to spin...but the bullet doesn't know whether it is being spun by 8 small lands and grooves or 2, 4, or 6 bigger ones.

If in fact more lands and grooves created more friction then logic (and physics) would dictate that a projectile fired from a barrel with 8 lands and grooves would have less velocity than the same round fired from a barrel with fewer lands and grooves. To my knowledge, this is not the case.

Like Shop Cart said...it really don't make much difference in practical terms.

Thanks fella's, I understand what your saying but I can't get the concept of rifle barrels having a range from micro grooving through to 8 grooves.

Just seems to me that there must be a reason for such a diverse range.

Twist rates I understand,projectile length and all that, but with barrel groove numbers is it just what takes the makers fancy or is there a valid reason.

PacNor for example offer the same barrel with either a 6(1-14)or 8(1-18),I would just like to understand why you wouldn't just offer one and stick with it if it worked.

Not knowing this bugs me!!

[QUOTE]Originally posted by mix3006:
Thanks fella's, I understand what your saying but I can't get the concept of rifle barrels having a range from micro grooving through to 8 grooves.

Just seems to me that there must be a reason for such a diverse range.[endquote]



First, you meed to accept the fact that the number of grooves has absolutely nothing to do with the twist rate. They are two different and basically unrelated items, other than that both are descriptive of some aspect of the barrel.

(Kind of like describing a car by listing the horsepower and the number of doors...both ARE pertinent to the buyer, but not necessarily dependent on each other.)

The twist rate is set to stabilize specific bullets fired through the barrel...a slower twist is needed to stabilize short length bullets than is required to stabilize long length bullets. So, for instance, a twist of 1 tun in 14 inches will reliably stabilize 50 gr. light weight (short length) .224 diameteer bullets, while a twist of 1 turn in 9 inches is a good twist to stabilize 69 gr. .224 (longer) bullets, and a twist rate of 1 turn in about 8" is usually required to stabilize the usually even longer 80 gr. .224 bullets. There are established formulas of long standing which allow you, a barrel-maker, or anyone else to calculate what twist rate which is required for a given diameter and length of bullet(pretty much always expressed in how many inches of barrel length it takes for the rifling to make one complete turn). Google for the "Greenhill formula" if you want to asee one of the oldest....

Different twists are offered becaue shooters interested in top accuracy and highest velocity want to use a QUICK ENOUGH twist rate to stabilize the spedific bullet length(s) they will be using, but don't want to use a twist which is unnecessarily quick.

The number of barrel grooves, on the other hand, is more a matter of philosophy and preference of the barrel-maker and barrel-buyer. Some makers & buyers believe that accuracy is increased by using more and wider grooves, leaving smaller lands, which in turn deform the bullet less as it passes through the bore, while still providing adequate grip to spin the bullet without it skidding across the lands. Others do not believe this is a significant advantage, but DO believe that it is easier to cut perfectly consistent and precise grooves if there are less grooves to cut.

As with all moot philosophical questions, that example is a gross over-simplification, but it will take you a lot of reading to learn most of the considerations involved.

To simplifiy your mental gyrations on the subject, just accept that the two (twist rate, and number of grooves) are not closely tied together in the practical everyday world of shooting. Pick &buy the twist rate correct for your bullets, and then read for a few years before tackling the problem of exactly how many lands & grooves the vbarrel "SHOULD" have. And don't forget to go shooting as often as you can [G}.

Alberta, that was a superb reply.

Perhaps you can now explain the wide range in tastes in wiskey and women.
Good luck!

Ed Shilen told me that he could not tell any difference in the amt. of lands and grooves in a barrel. He makes different ones because if a certain amount makes you feel good get it. Butch

Thanks gents; this obviously comes down to a personal preference and nothing more.

Unless you are shooting cast bullets, then you want/need fewer but deep rifling "Ballard type".

I don't know if there is any truth to it but I have heard/read that some believe that barrels with fewer lands and thus wider lands will have a slowed rate of throat erosion.

quote:

Originally posted by Alberta Canuck:
[The number of barrel grooves, on the other hand, is more a matter of philosophy and preference of the barrel-maker and barrel-buyer. Some makers & buyers believe that accuracy is increased by using more and wider grooves, leaving smaller lands, which in turn deform the bullet less as it passes through the bore, while still providing adequate grip to spin the bullet without it skidding across the lands. Others do not believe this is a significant advantage, but DO believe that it is easier to cut perfectly consistent and precise grooves if there are less grooves to cut.

}.

Truely well done

In passing since you broached the topic ; as a point of interest the initial pressure jump is affected by the lans to groove bareing surface ratio. Of course the more bullet deformation as the bullet passes into the rifling the faster the pressure rise.

The more grooves there are the greater the sharing of the total thrust force on the forward groove walls yeilding less barrel ware. This is only true ,however, if we are comparing groove deapths that are equal. roger

quote:

Originally posted by hawkins:
Perhaps you can now explain the wide range in tastes in wiskey and women.
Good luck!

At least when it comes to whiskey I have yet to meet anyone that didnt like Rebel yell, knob creek, Crown Royal, Jim Beam, or Seagrams 7.

Women?...that's a different forum I think.

If you want to see some wacky looking rifling take a look at the "Metford" type used on some English and Japanese rifles in the 1930's. It looks like an out of round bore because the grooves are not cut square, they are oblong in shape.

quote:

Originally posted by vapodog:

quote:

Originally posted by hawkins:
Perhaps you can now explain the wide range in tastes in wiskey and women.
Good luck!

At least when it comes to whiskey I have yet to meet anyone that didnt like Rebel yell, knob creek, Crown Royal, Jim Beam, or Seagrams 7.

Women?...that's a different forum I think.

Wow ! Are we in the same league or what? How about black berrey brandy mouth wash just after you throw the snow covered tarp off you. Yes you can swallow and who the hell let the fire go out? roger

Hawkins asked for an explanation of the wide range in tastes in whiskey and women...

That's easy!
More whiskey widens ones range of women.

Too much whiskey increases ones range of wide women!

Been there!!

One thing I was considering was that an odd number of lands would mean less compressive force on the bullet as it is forced down the bore. An even number of lands would have two lands always opposite of each other and would force a .308 caliber bullet to squeeze down to .300. While an odd number of lands would force the .308 bullet to size down to .304 instead.

Would this reduce the pressure required to engrave the rifling on the bullet?