What the heck is the "lands"

[nvarcher]

I have been reading up on reloading and I always see they seated the bullet .xxx inches off the lands. What does this mean?? Is there a set overall length for this for each caliber or how would I find it??

 

[MOHunter]

The seating depth at which the bullet "lands" against the rifling, or more simply touches it. You don't want the bullet to actually touch anything while in the chamber due to potential pressure issues. You'll see the gap referred to as "jump" in your readings. Most things I see recommend starting your seating depth .010" off the lands and working back (deeper seated bullet so more jump) until you find the best accuracy. Hornady makes a great simple tool for this called the OAL gauge.

 

[Retterath]

Mohunter is right on. Good explanation.

 

[Colorado Cowboy]

The seating depth at which the bullet "lands" against the rifling, or more simply touches it. You don't want the bullet to actually touch anything while in the chamber due to potential pressure issues. You'll see the gap referred to as "jump" in your readings. Most things I see recommend starting your seating depth .010" off the lands and working back (deeper seated bullet so more jump) until you find the best accuracy. Hornady makes a great simple tool for this called the OAL gauge.

While the explanation is basically correct, the definition is not. In a rifled barrel, the lines you see are the slices cut out during the machining process and are called grooves. They are spiraled and impart spin on the bullet. Terms like I in 13 are used and refer to the amount of twist eg. one full rotation every 13" of barrel length. The number of grooves cut are usually termed as a 2, 3, or 4 groove barrel. The area left uncut by the broaching tool is called the lands.

 

[nvarcher]

So from my understanding when the cartridge is at max col is when it is touching the lands and you back it off from there. Is that true or am I way off?


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[Musket Man]

It really depends on your chamber, there is some variation in them. In some guns the bullet may not be touching the rifling at max COL, while the bolt wont close in others. Factory ammo is seated deeper so it will work in any chamber. The factory loads I have measured have all been about .001'' less then the COL listed.

 

[Colorado Cowboy]

It really depends on your chamber, there is some variation in them. In some guns the bullet may not be touching the rifling at max COL, while the bolt wont close in others. Factory ammo is seated deeper so it will work in any chamber. The factory loads I have measured have all been about .001'' less then the COL listed.

MM is correct. The distance between the end of the chamber and the beginning of the rifling is called freebore. Some rifle mfgs use lots of freebore like Weatherby.

 

[libidilatimmy]

COL maximums are industry wide standards used in the manufacturing of ammunition that I think have more to do with fitting in magazines than anything. As every type of bullet has a different measurement from the tip of the bullet to the ogive, the term we should be talking about to be more accurate is CBOL (Cartridge Base to Ogive Length) because this is the point on the bullet that comes into contact with the lands, that has a specific diameter for every caliber, at a specific length with the tip protruding into the barrel a smidgen, if that makes sense. Depending on the bullet, the CBOL for when the bullet makes contact with the lands will produce a COL that exceeds maximum industry standards and may not fit in the magazine of your rifle depending on firearm manufacturer.

 

[Colorado Cowboy]

COL maximums are industry wide standards used in the manufacturing of ammunition that I think have more to do with fitting in magazines than anything. As every type of bullet has a different measurement from the tip of the bullet to the ogive, the term we should be talking about to be more accurate is CBOL (Cartridge Base to Ogive Length) because this is the point on the bullet that comes into contact with the lands, that has a specific diameter for every caliber, at a specific length with the tip protruding into the barrel a smidgen, if that makes sense. Depending on the bullet, the CBOL for when the bullet makes contact with the lands will produce a COL that exceeds maximum industry standards and may not fit in the magazine of your rifle depending on firearm manufacturer.

Also correct.

 

[canvsbk]

Very nicely put gentlemen. A bit off topic but my experience with my rifles is that with the short action calibers the COL that's best for accuracy is too long for the magazine. That's just me and my stuff.

 

[Don K]

Now hold on a second here!!!

I'm learning something here reading this.























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