BARREL TWIST RATES AND GROOVING

[snyper]

I have originally posted this inquiry on another (foreign) forum:

I have a question regarding barrel twist rates and grooves. I have been searching for any info on the web but have not stumbled upon it yet. So maybe someone here may have some insights.

First is about barrel grooves, Is there any advantage (or difference) in performance (accuracy, speed, power) when two different barrels are used on one gun, one with say, 6 grooves versus one which has 12 grooves.

Second, is the twist rate of a barrel, assuming all else is equal except one barrel has a slower (is that the proper term?) than with a faster one. What factors does it affect, accuracy? knocking power (on prey)? velocity? etc.?

Would there be an ideal combination of number of grooves and barrel twist in relation to FPS that you would like to achieve if you are designing/building an airgun.

Any experience you may have in test you may have done is highly appreciated.

Good day to all!

[snyper]

This is a reply from LD (Larry Durham)

From:ld ([e-mail]
To: snyper71


for regular pellguns, I think a twist rate of around 1-15 is about average. I have tested rifling from zero twist to around 1-6 and seen good results with all. As to the number of lands or grooves, I've seen some with many, and some with few, and again, seen good results with all of them sometimes.

My feeling is airgunners WANT these traits to be important because they are most able to measure them. Since I have had opportunity to shoot hundreds of barrels of the same design, manufacture, and specs, yet have seen many good, but some bad ... I know these two traits, in themselves, arent that important. BTW, I have taken some of those "bad barrels, and made em "good" without messing with twist or groove count.

Besides how MANY grooves, I think the depth of each individual goove is important, as is the width of each individual groove, and of course, the bore diameter from one end to the other .... and the relative smoothness.

If I could make really good barrels myself, I'd say the most important part is to get good straight blanks of perfectly homogeneous material of the spec. desired (i would prefer SS type 304 i think. Next would be the ability to bore perfectly centered, straight, true holes with a fine finish. Then ream to nearly correct size, and hone to perfection ... not too smooth, not too rough. Then draw a nice button through to form around four shallow grooves.

I'd start with four wide shallow grooves, and work my way thru three and two grooves. Why so few? Less chance for them to vary from each other.

But, since I can't make my own, I just trust to the barrel makers, and buy from those I think make good ones.

[winnie54]

good morning sir ! for a long long time i really want to ask somebody who really knows barrel and grooves. pls. allow me to ask you again. Is there an advantage if the rifle barrel is 18.4 inches and is said to be l8 grooves? what about the barrel of 'naning' of manila(may he rest in peace), 20 inches and has 16 grooves?? What is your opinion ..sir mas marami na kayo tests na ginawa , i trust your HO on this matter.