"Jamming" bullet into the lands?

[mytwo60]

So I read thru this thread. Went in the garage and "jam" 2 empty cases. One case is Remi brass and the other is Lapua. The remi brass is about .005 shorter than the Lapua brass.

So this got me thinking that neck tension is very important in finding this "jam" measurement. Right now I am only partial sizing the neck on my brass. I am sure the the "jam" measurement will differ if I fully size the neck.

So which "jam" measurement is correct? Damn it. I am in a "jam" now.

 

[TnTom]

The jump or jam to me is where you seat to fine tune your workup. In my world I measure the bullet used with the Stony Point setup, the reading I get is the "touch". I take that measurement and try different seating depths, if I seat it .010 longer I call that 10 thousands jam. If I seat it .010 short, I call it a 10 thousandths jump.

Seems striaght forward to me.

 

[jo191145]

The jump or jam to me is where you seat to fine tune your workup. In my world I measure the bullet used with the Stony Point setup, the reading I get is the "touch". I take that measurement and try different seating depths, if I seat it .010 longer I call that 10 thousands jam. If I seat it .010 short, I call it a 10 thousandths jump.

;D ;D ;D We live in the same world.
Stoney point,,,just touching,,, jam or jump. Does'nt get much easier.
Very rare that I unload a cartridge and look at the marks.

I have no problem with folks using other methods. I'll be doing my own testing anyway so what works for one may not work for me.

 

[jo191145]

So I read thru this thread. Went in the garage and "jam" 2 empty cases. One case is Remi brass and the other is Lapua. The remi brass is about .005 shorter than the Lapua brass.

So this got me thinking that neck tension is very important in finding this "jam" measurement. Right now I am only partial sizing the neck on my brass. I am sure the the "jam" measurement will differ if I fully size the neck.



So which "jam" measurement is correct? Damn it. I am in a "jam" now.

Your thinking is correct. Any changes to the brass will have an impact on readings.
For one, stick to one sizing methodology and brass type.
Two, remember, its just an arbitrary number you select in which to begin testing.
If you find your bullet shoots best .010" jammed but its really .020" jammed who cares. ;D

Thats one reason buying in bulk is advisable. A different lot of the same bullet might require a little tweaking.