Chamber Dimension Nomenclature

givette

I've been told the 'freebore' is the unlanded portion of the barrel. No rifling exists.

Now, leade..I've seen different 'leade' dimensions.

Could leade be the distance from the beginning of the land, to the point where the lands achieve full height? I'm sure there are different ramp angles to the lands in various designs, (where the rifling begins), and that equates to the difference in total ramp length.

My question:
Are freebore and leade the same? If so, then what is the [item in blue, above] called? Thanks, Joe

1KYDSTR

As I have always understood it:
1) Leade is the length from where the rifling begins to where it achieves full land height.
2) Freebore is the area from in front of the bullet where chambered to where the leade begins.
So if I understand the terms (and there is serious doubt I really have that good a grip on it!) then NO, the terms are not the same; I don't believe freebore is intended to include the leade, it is just the area in front of the chamber neck step to the beginning of the leade where there is no rifling extant. Interested to hear NoNonSenses' take on this...he and others will have a definitive answere.

nononsense

givette,

We cover this regularly because it seems to need a refresh for new members. There is some information in 'search' complete with drawings that I've written over the last several years.

In a nutshell:

If we start by naming the neck of the chamber which everyone agrees with, the next feature is the Transition Angle which is 45 degrees.

The next feature in front of that is the Leade or the straight line portion of the chamber which does not contain the lands but is just slightly larger that bullet diameter. This is often termed 'freebore' since the bullet has no contact with any surface of the chamber or rifling. Not all chambers use Leade or what is often called freebore.

The next and last feature is the throat which is a funnel shaped design which allows a smoother transition from no contact with the rifling to full contact. This is often expressed as an angle in reamer drawings, usually 1 degree 30 minutes these days for modern cartridges.

I am out of position from my database so it will be later today before I can add illustrations or photographs. If you need reinforcement for these features, go to the Pacific Tool and Gauge website for reamer drawings and look at the labels on those drawings.

Best.

givette

In one word, It's called Throat!!

Nononsense, no need to post a graphic. I got it. All I needed was the name for it. Thanks again. Best, Joe