30 cal rifling
 

What is the difference between 30-30, 30-06 and 308?

I want to know the differences in rifling and size. When you buy to reload a pack of bullets just says 30 cal.By looking into a 308 and 3006 and 3030 barrel could the difference be seen?I just don't have all three to compare. I am getting into the physics behind this stuff...

I am really into this rifling "stuff" Really cool stuff.

The rifling refers to the grooves in the barrel that impart spin to the bullet. The rifling in most .30 caliber barrels is one turn in, between 10 & 12 inches. This will stabilize most .30 caliber bullets, 130 to 200 grains. It would be difficult to determine by eye. Most companies reference the rifling spin in the spec.'s of their rifles. You can determine the rate of twist by putting a tight fitting cleaning rod into the muzzle and mark a line along the cleaning rod. Push the cleaning rod through until you see the line again. The distance you pushed the rod through is your rate of twist. There is actually a formula that is used to determine the ideal rate of twist.

Bullets for a 30-30 Win must be a certain design due to the tubular magazines, and the manufactures will identify which bullets are approved for the 30-30 Win. You must not use a spire point, hollow point, FMJ or any type of bullet that has a point in a centerfire rifle with a tubular magazine. The bullet point may set off the primer of another cartridge in the tubular magazine when loading the tubular magazine, during recoil or if the firearm is dropped, etc. Use only bullets approved for the cartridge being reloaded.

And all the bullets are .308" diameter. Some are just designed for lever actions (flat point) and others for higher velocity rifles.

1:10 would stabilize a 110 to 200gr bullets, Factory twist rate.
1:12 would stabilize a 100 to 175gr bullets
Approximate weights, Velocity can effect what you can shoot out of them too.

Welcome to the party...
 

The easiest way to check a rifle's twist rate is to use a tight fitting cleaning patch, a cleaning rod, a magic marker, and a piece of masking tape.

Insert the rod with the tight patch into the bore a few inches. Wrap a piece of tape around the rod and fold it so it makes a small "flag". Mark the rod at the entrance of the chamber guide, and note the position of the flag. Then push the rod into the bore slowly until the flag has made one complete turn. Again, mark the rod with the marker at the entrance of the guide. Push the patch out of the bore, then pull the rod out and measure between the marks. You can also usually google your rifle model number and typically find the twist rate it was designed with. Occasionally (rarely), the barrel will be stamped with it's twist rate, but this isn't always accurate.

As far as rifling rates for different cartridges go, there is a fairly simple way to calculate the necessary twist rate to match a caliber, bullet weight, and muzzle velocity. Google "Greenhill formula" or "Greenhill twist calculator" and you'll find a ton of information. Basically, the heavier a bullet is for a given cartridge, the slower the muzzle velocity will be, and the faster twist it will need to stabilize. For example, a 40grn bullet in a .223 Rem at 3500fps will stabilize in a 1 in 10twist, while match barrels, that are designed to use 70grn bullets at 3000-3100fps will require a 1 in 7.5" to 1 in 8" twist for maximum stability. The faster a bullet's muzzle velocity, the faster it will spin (rpm) for a given twist rate. Alternatively, the faster the twist rate, the faster a bullet will spin for a given muzzle velocity.

Here are a few formula's, just to get you rolling....

rpm (revs per min) = muzzle velocity (fps) * rifling twist rate (turns per inch) * 12"/ft * 60sec/min

Greenhill twist: twist rate required for a bullet with muzzle velocity below 2,800 fps: twist rate = (150 * D^2)/L * sqrt(SG/10.9)

For muzzle velocities over 2,800fps: twist rate = (180 * D^2)/L * sqrt(SG/10.9)

where D is bullet diameter in inches, L is bullet length in inches, SG is specific gravity of the bullet, which is approx 10.9 for lead core bullets (this term cancels out for lead core bullets). Specific gravity can be determined by measuring the volume of the bullet by dropping it into a graduated cylinder, and determining the actual mass by weighing the bullet. In general, 10.9 works pretty well.

Rifling rates are just the tip of the iceberg for the science behind ballistic behavior. One of the chaptes in my older version of a speer reloading manual is titled "why ballisticians go grey"... This is definitely NOT a joke...

Have fun with it...

Certain Calibers/Rifles are good for specific types of Hunting and different size and types of Game Animals...some caliber Rifles are good for several different size Animals.The 30-30 Caliber Rifles are great for thick brush and shooting distances of 50 to 150 yards or better if You can use the newer Lever_Revolution shells/bullets from Hornady,The 30-06 Rifle is great for longer distances and bigger game animals from Hogs,Deer to Mule Deer and Elk...the .308 is another good High-powered Rifle that can take down Big Game Animals and shoot long distances.Another thing to consider is the different grain weights available in the 3 mentioned calibers,a lighter bullet will travel faster yet it can be caused to glance off target if it happens to hit thick brush,tall grasses,limbs etc...!Lots of different variables and things to consider when choosing a certain Caliber Rifle and what You intend on doing with it...will You be target practicing,hunting smaller game like Varmints/Predators Coyotes etc...or will You be hunting Deer or bigger Game Animals?

30 caliber bullets
 

all three are 30 caliber bullets. officially they are .308 in diameter. they just have different uses. the 30-30 have to have round nose or flat nose if used in a rifle with a tube feed. actually they can all be loaded in all three rifles as they are the same caliber. get a rifle loading book and it will tell you all about bullets and how to load for them.