the micro groove is button cut and ballard is the lands and grooves are not equally spaced
Marlin switched from Ballard rifling to the newer micro-groove on their 81 DL model in 1954.
It is Ballard style rifling, and should date to 1999. The year of manufacture is 2001. 1st 2 digits of serial # correspond to the year it was made. Ballard rifling is correct.
Can be hammer forged, cut or drawn.
Smoothbore: muskets, musketoon, carbine, blundebuss, howitzer. Rifling made a great difference to accuracy of firearms. I would add to that Mortars.
A musket is smooth bored, like a shotgun's bore. A rifle has rifling inside the bore (grooves).
Rifles have spiral grooves cut into the inside of the barrel, known as rifling. Muskets are smoothbore. Rifling causes the bullet to spin in flight, permitting accuracy at long ranges. Also slower to load.
When rifled, the rifling tool cuts the GROOVES. Material left between the grooves is the LANDS.
In relation to firearms, it has to do with the rate of rifling in the barrel. Rifling is the spiral grooves that puts a spin on a bullet to increase it's accuracy. "Barrel twist" is the rate of spiraling or inches per turn. That is the length of barrel it takes to spin the bullet a full 360 degrees.
Length, rifling (sometimes)
A rifle is a firearm with a shoulder-stock which is used to propel a bullet to strike a distant target. The Rifle is distinguished from the muskets of eras past, by the presence of 'rifling'. Rifling is the presence of spiral grooves cut into the interior of the barrel. Rifling induces a spin on the bullet resulting in more stable flight through the air. This spin has the effect of making the firearm more accurate by not only giving the bullet a straighter flight-path, but making the rifle's point of impact more consistent. (Consistency allows the user to properly adjust his sights to ensure his bullets hit where he or she aims.) Previous firearms such as muskets had no rifling. Today shotguns have shoulder stocks, but are typically smooth on the interior and have no rifling. (Some shotguns with rifled barrels exist to shoot specialty 'sabot' ammunition. While still called shotguns by the shooting community at large, the correct term for these firearms is Bore Rifle.) Modern handguns also incorporate rifling, but lack shoulder-stocks and are referred to as pistols.
Not sure when they went from micro-groove to Ballard type but they went to micro-groove rifling around 1954,a 1 in 38 twist is standard for most .44 Magnum &.444 but with some ammo makers making factory loads that use bullets that weigh more then 240grns. in weight buy a Ruger Deerfield simi-auto .44 magnum or their lever action .44 magnums because they have a rifling twist of 1 in 18 that will stabilize the heavier 300grn.plus bullets and don't use the micro-groove rifling,also leading can be a problem in micro-groove barrels if your using soft lead and load them to more then 1200 feet per second so for that reason your better off to stick with jacketed bullets of not more then 240 grains when loading ammo for rifles with micro-groove barrels with the 1-38 twist if your going to be using heavy loads.Hope this info can be of some help to somebody, I have also noticed that the Ruger Deerfield rifle with the faster rifling twist gives a better bullet mushroom as opposed to the old 1-38 twist.If you'd like to learn a little more about this fascinating topic,type rifling characteristics into a search with Google and you will find a lot of interesting information on different types of rifling used by different manufacturers. New .444's now have a 1 in 20 twist. I hope they do the same in the .44 Mag soon. The 1 in 20 will stabilize 300 grain bullets while the 1 in 38 will not.
RIFLED firearms are those that have a method of making the bullet spin when fired. This makes for a much more accurate projectile. The oldest and most common means of doing this is buty cutting spiral grooves on the inside of the barrel. These grooves grip the bullet, causing it to spin as it passes up the barrel. The grooves are known as rifling.