Bullet Seating Depth, Touch vs Jam

[60723]

Measuring a broken in barrel.
Hard Jam 1.730 CBTO
Touch 1.718 measuring with Hornady tool. Repeatable to .003-.005
Touch 1.706 measuring with stripped bolt. Repeatable to .001-.002
Was having issues with the falling bolt until I removed the extractor.

 

[6BRA]

If you do a soft seat method light neck tension, jam the bullet with the bolt, and the eject. Bullet sticks. Remove the bullet from your bbl, now examine the marks. Put calipers on marks and my experience, the marks are .100 long..or more, hard jam. So touch would be .100 off? Or if one backs off .020..you are .080 in? The marks on the bullet don't lie.

 

[6BRA]

So in quickloads based on touch and hard jam...where does shot start pressure increase...at touch or jam? Considering it can be quite a distance...

 

[No manches"]

^^^good question!

 

[6BRA]

That's why they say work up....for someone to have only .020 to .030 mark on a bullet would indicate a very very shallow lead...in my mind. At hard jam the bullet will not compress any farther..without pressure/ bang!

 

[Tesoro]

Now load a dummy round with the same bullet, make it about .025" longer than that measurement. Remove the firing pin if you can and gently close the bolt. If the bullet sticks in the bore, remove and seat it at .020" OAL. Rub the dummy bullet with 0000 steel wool; reset it and try again. Now examine the bullet. If possible, use a loupe or magnifier and You should see faintly a square mark where the bullet touched the lands. Lower the seater die by .005" and repeat until the square mark disappears. You will have found the point of contact to begin seating. Write it down. Re-check it periodically to determine when the throat has begun to erode, and repeat it again.

Exactly!!! I would add it can help to scrub the throat area beforehand.