Height of Hills in a Rifled barrel

[Nick93]

Hi ! I would like to know how tall are the hills of a pistol and a rifle barrel since I have searched every place in the internet and nothing. My major concern its in a 9mm pistol barrel for what I understand every manufacturer has it owns standards when it comes to barrels but there must be an average right ?

BTW the question is referred to conventional rifled barrels not polygonal or conventional rounded rifling

Thanks in advance

 

[7.62 Nato]

I believe the common terms are lands and grooves referring to the barrel rifling.

 

[Hacker15E]

I don't think they're called "hills" if it's not polygonal rifling -- the term you're looking for is "lands".

I don't know what the average height in a 9mm barrel is.

 

[rcmodel]

It depends on the caliber.

A typical .30 cal rifle has a .300" bore, and .308" grooves, making each land .004".
A typical .22RF has a .217" bore and .222" groves, making each land .0025".
A typical 9mm has a bore diameter of .346" and groove diameter of .355", making each land .0045".

However, no 9mm is typical.
There have been a gazillion makers over the last 100 years, each marching to a different drummer it seems.

rc

 

[Jim K]

Just to clarify a point. The bullet is groove diameter, so that a .30 caliber rifle with a .300" bore diameter and .308" groove diameter fires a .308" bullet.

When naming cartridges, cartridge developers or ammunition manufacturers may call it by either diameter; for example, the .30-'06, .30-30, .300 Winchester Magnum, .308 Winchester, .308 Norma Magnum, all use a .308" diameter bullet.

Jim

 

[YankeeFlyr]

Or neither diameter, like .38 Special or .223 Remington.

 

[Zednut]

Typical differences on lands and grooves fall into a range of .0015"-.004" or if measured using the diameter differences, about .003"-.008". As for the effect on the bullet and the ability to properly get it rotating at its optimum stability speed, other things are considered.

The shape of the lands and their shoulders to the grooves plays a significant role. More importantly there is a ratio that can be worked out between the grooves and lands. Typical ratios are 60:40 for heavily rifled barrels and 75:25 for lighter rifled barrels. A more recent term has evolved lately in rimfire barrels called MI (minimally invasive).

When the ratio gets very high for the groove to land relationship and the actual groove diameter more closely approaches the actual unfired bullet diameter, the bore is regarded as being MI...in other words, it disfigures the bullet less than a more traditional bore/rifling set up. In lead bullets (especially rimfire) this reduction in bullet disfigurement has been equated to better accuracy by some folks....provided the bullet still gets stabilized properly from the twist.

 

[Nick93]

I believe the common terms are lands and grooves referring to the barrel rifling.

LOL maybe that's why I didn't find nothing in my search

Dang I hate my English

Thanks to all your replies helped a lot

 

[Ditchtiger]

LOL maybe that's why I didn't find nothing in my search

Dang I hate my English

Thanks to all your replies helped a lot

Had me wondering