Rifleing Question

[Bradster]

This may be a dumb question but im gonna ask anyway.

I think i know how rifleing or twist works in a gun, like 1 in 9 means 1 full twist in 9 inches, and i know they say that the quicker the twist the better for heavy bullets to stabilize. My question is this, how many groves are in an average barrel? Like are there a few different groves all cut at 1 in 9 or is there just one? Looking down the barrel it looks like there are a few.

Second is there a way to tell what the twist rate is if it is not documented somewhere? Like can you put something in a barrel and count the turns?

Like i say this may be a dumb question but i know all of my AR's have like 1 in 9 or close to that and i shoot small bullets from the rifles and larger bullets from the AR's.

Reason i ask is that i recently picked up a 22-250 and from what i am guesing from reading some stuff it has a 1 in 15 twist. that seems odd to me, but who knows.

[normanvin]

You can measure the twist by using a cleaning rod and a mop. The cleaning rod should also have the swivel bearing. Start the mop into the bore. Mark the rod with a sharpie, at the start of the barrel. And at a spot that you can count the rotations. push the rod into the barrel, stopping when the rod has made one rotation. mark the rod at the barrel.

Remove the rod. Measure the marks. You then know the rifling twist one time in that distance.

[Arch007er]

I'll try to get you in the ball park till TOMCAT comes in and smacks ya with a boat load of info. But I think your .22-250 with a 1 in 15 twist is designed to shoot 50 grains and below (bullet weight) My pops 6 BR is a 1 in 12 and he can shoot 60-70 grain weight bullets and the other barrel was a 1 in 14 and that only liked 50-55 grain bullets.

[Bradster]

I may be wrong, i think this rifle is 1 in 14 not 15.

[knight0334]

The other factor in rifling is velocity.

1. The longer the bullet the faster the twist you need
2. The faster the bullet the less twist you need
3. The shorter the bullet the less twist you need
4. The slower the bullet the faster the twist you need

Now you have to combine the velocity and the length to figure out which is the proper twist rate. For an 22-250 with a 1:15", you should be looking at the higher velocity varmint pills no more than 55gr, probably around 40-50grs.

Examples: a 69gr .224" bullet from a .223Rem/5.56 will need about 1:7" because of it's slow velocity and long bullet. But if you shoot that same 69gr bullet out of a 22-250, 225Win, 224Wby, 220swift, or 223WSSM - you might only need a 1:12".

Typically in a Ballard rifled firearm there are 4-6 lands/grooves depending on make and other factors. Marlin in their "MicroGroove" bores have 19-30.

[Poonie]

This may be a dumb question but im gonna ask anyway.

My question is this, how many groves are in an average barrel? Like are there a few different groves all cut at 1 in 9 or is there just one? Looking down the barrel it looks like there are a few.

.

Depends. I've read of barrels in certain British Enfields that had only two rifling grooves. Other guns have 4, 6, etc. Marlin makes what they call microgrooves, instead of say 4 or 5 larger grooves, Marlin will cut say 8 shallow grooves to make their rifling. Then you have different styles of rifling such as the old Metford (I think its called) style where there is hardly any groove at all in the chamber throat and muzzle areas of the barrel, and thicker grooves in the center of the bore. The Japanese Arisaka rifles have this style and when viewed with the eye makes it appear that the rifling is worn out when in fact its not. You laso have left hand twist, right hand twist, and what have you. There have been and are many different types of rifling to suit many different applications. I'm sure I've left out alot but this hopefully will help you to understand the complexity that is rifling.

[Tomcat088]

Lol, I've been busy but glad to see that he's been getting some correct answers from everybody. I guess I'll try to fill the shoes that Archer was talking about and add some mostly useless info that you didn't know to the conversation. As others have stated, twist rates and what a bullet needs will depend on lots of things, velocity, bullet length, bullet weight, etc, but there's also some other variables.

Atmosheric variables can greatly affect how a bullet stabilizes. The twist rates that you see are for sea level, with a specific humidity, temperature, etc (basically air density). If you are at a higher altitude than sea level, sometimes you can get away with "less" twist than you "should be able to". There are people that live in the mountains, or high plains that can shoot 190 and 210 grain bullets out of their .308's, with a 1:12 twist, which typically isn't enough to stabilize those bullets at sea level. Due to differences in the air (it's thinner), the bullet may not need as much twist to stabilized; but keep in mind this is relative to temperature, barometric pressure, velocity, bullet BC, etc. This means you might have a load that shoots great in the summer, but keyholes in the winter, if you're fiddling around with minimum stabilization. It also means that if you have a pet load for heavy bullets with minimum twist in the mountains, if you take it to shoot a match at sea level it might not stabilize.

Realize also that bullets can be overstabilized. It does not hurt a bullet to be slightly over stabilized, but if it is greatly overstabilized, it changes the flight characteristics of the bullet. When an overstabilized bullet reaches the peak of the trajectory, due to the gyroscopic stabilization, it won't nose over properly and will begin to fly with the nose up. When this happens it creates a small amount of lift due to the pressure difference on the different sides of the bullet (top and bottom). This slight amount of lift makes the bullet appear to hit high and right (because of the rifiling twist), from where it should be expected. At shorter distances it just might open your groups up a little bit, but at long ranges it makes quite a difference. Just some fun stuff to think about.