Finding lands !

[CNC-Dude]

The Datum Dial does not find land contact. That's not what it's for.
You can measure your shoulder or CBTO with it.
Okumacaptain, you're using a good method/tool, but your variable is neck seating force.
You need to remove that variable

​

Also, if I'm not mistaken, Eric actually uses jamb minus .020", and .023", and minus .026". Not touch, because as he mentions there are varying degrees of touch before you reach the jamb point. And he says you can be into the lands by a good amount depending on neck tension. So, jamb is a more static and finite starting point he says for his seating depth method.

 

[mikecr]

Jam is not better, as it adds even more friction to more or less ogive radius, which is adding friction variance.
Alex's trial & error method works, and a split neck case works, or no case at all with a downward pointed barrel, and the bullet with a pencil resting on it to indicate bullet lift from lands. That goes back to the old cleaning rod method, which works perfect.
I use an R-P Tool for that(obsolete).

 

[Shooter13]

The Datum Dial does not find land contact. That's not what it's for.
You can measure your shoulder or CBTO with it.
Okumacaptain, you're using a good method/tool, but your variable is neck seating force.
You need to remove that variable

​

You are correct, BUT once found (touch and depending on if you are looking for jam or off the lands) this gauge is very reliable and consistent.

 

[Okumacaptain]

I can get within .001 of the stripped bolt method just using my L&L oal tool coupled with a fire formed modified case.
So if a dumb ass farm boy like myself can get a repeatable measurement I’m pretty confident a machinist can as well.

I’ve been trying different ways and nothing seems repeatable . Closest I’ve found is a Flat base bullet inserted upside down . But the measurement differs quite a bit from a profiled bullet .

 

[Okumacaptain]

The Datum Dial does not find land contact. That's not what it's for.
You can measure your shoulder or CBTO with it.
Okumacaptain, you're using a good method/tool, but your variable is neck seating force.
You need to remove that variable

​

You were so right ! I mandreled the neck up so there was only a very light resistance on bullet and SHAZAM I’m getting readings within .001-.002 !

Thx Much !

Mark