Gun Terminology Question

O

Old Timer

Guest
When you talk about how far off of the lands that a bullet is before it is shot, is there a term for this, I know it is not headspace. But what??
 
Bullet jump

I thought it was called "leade". Probably mistaken as usual.......but thats what I have heard it being referred to for years.....
GRT
 
lead/leade is a component of the chamber/reamer, NOT a component of loading/bullet seating depth.

off the lands, in the lands, bullet jump....

mike in co
 
Now not probably!

See I told you I was probably wrong, guess all these years I was calling it that mistakenly. Thats what I'd always thought it was anyway. Please accept my sincerest apology and I thank you gentlemen for correcting me. I learned something else today and I thank you for that too!
GRT
 
The thing that limits how far a bullet may protrude from the case neck of a loaded round (if it is limited) is the constriction that starts where the lands begin ahead of that portion of the chamber designed to house the case neck. In the case of many target style chambers the ends of the lands are chamfered from zero to full height at an angle of one and one half degrees in relation to the centerline of the bore. If a bullet just makes contact with the angled beginnings of the lands, without being significantly marked we say that it is "touching". With any loaded cartridge length ,(with that particular bullet), that is shorter than one loaded so that the bullet just touches the beginning of the rifling will have the bullet at some distance back from the point at which it first makes contact with the angled beginning of the lands. This is the distance off of the lands, also referred to as jump. Conversely when a bullet is loaded to a longer cartridge length (than touch) it is said to be into the rifling by the amount longer than a round loaded to just touch. Another term commonly used is jam. This is the maximum length that a given bullet, at a given neck tension can be loaded to without the bullet being set back in the case neck when the bolt is closed. Many believe that referencing loaded bullet position as so much off of (less than)jam is more conveinent than referencing the touching length, primarily because all that is required to determine this lenght is to load a round (or dummy round) long and then chamber it, in the process pushing the bullet back to jam length. (I know that this is overly wordy, but I believe that it is correct and I am too tired to clean it up... maybe tomorrow.)
 
Nope, not freebore either ;)

Freebore is another physical chamber attribute or component. In simple terms freebore is an area of the bore which has been bored ONLY to knock the lands off of the rifling while leaving the grooves essentially untouched. It has nothing to do with bullet jump UNLESS it's soo incredibly long that the bullet simply cannot span the gap.

Freebore is the smooth or unrifled section between the case mouth and the leade or tapered transitional area which denotes the start of the rifling lands.


This reamer print shows the parts rather clearly with the freebore being .0450 long.

http://eddavis3.homestead.com/files/6PPC_Davis.jpg


This thread gives some explanations of some of the terminology.

http://www.benchrest.com/forums/showthread.php?t=50298&highlight=chamber+print+leade


Here's another fairly recent thread on the subject.

http://www.benchrest.com/forums/showthread.php?t=29415&highlight=chamber+print+leade

I probably should scan in and throw up some PPG reamer prints as they're clearer but I think y'all can get'cherdrifts straightened out from these eh ;)


hth


al


al
 
Free bore... leade... headspace... are not adjustable by the shooter... they are fixed when the gunsmith chambers the rifle.

Bullet jump is adjustable by the reloader and it is what it is...
 
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