Bullet Seating Depth Measuring Problem - Touch, Jamb, or ?

[stomp442]

I would use the shortest of the measurements or do it again and then use the average of the three for your measurement to the lands then adjust your seating depth from there.

Personally I have never had more than one or two thousandths difference when using this method.

[82boy]

To start are you measuring the bullets, by ogive, or total length? Different bullets will have different ogive lengths, but the seating depth where it contacts the ogive will be the same. As you start out at a heard jamb (chambering hard.) you will see the lands engrave on the bullet, and there will be 3,4,6 marks depending on the type of rifling you have. At this point if there is marks missing you have a crooked chamber. Now the marks should be rectangular. (longer than they are wide.) Now taking the bullet and spinning it in 0000 steel wool, and polishing the marks off, now you will seat the bullet into the case deeper by .005. This time you should see the marks get more square, or equally long as they are wide. This is what many call jamb. Now again polish off the marks with 0000 steel wool, and move the bullet .005 more into the case. At this point you should see the marks getting faint they will be rectangular in the other way they will be wider, than they are long, and the rear edge of the marks will be light, and undefined. Now polish off the marks again and seat the bullet .005 off, and at this point you should not see any marks on the bullet. this is close to just touching. You will have to move the bullet out in small amounts until you just see a faint mark on the bullet, and this is touching. Regardless this is your reference point.

[beartooth91]

As indicated above, since I'm using the 30 cal comparator; I'm measuring by ogive length.
And, I never saw any of the rectangular or square marks you describe, even with a hard jamb. Only the circular scoring ring, around the ogive diameter, which gets thinner, fainter, eventually breaking as I seat deeper.

[82boy]

This is what the marks should look like this is out of a 4 grove barrel so there is 4 marks around the bullet, see how they are long and rectangular this is a hard jamb.
http://i34.photobucket.com/albums/d145/82boy/IMG_0641_zps1da965a5.jpg (http://s34.photobucket.com/user/82boy/media/IMG_0641_zps1da965a5.jpg.html)

[82boy]

It is hard to capture all the detail in a photograph, the picture looks more like a jamb, as the mark looks square. but the actual result is much different.

[beartooth91]

...uhh....I can't see any marks, your photograph..... and I have my glasses on.

[82boy]

How about now.
http://i34.photobucket.com/albums/d145/82boy/IMG_0641pointmarked_zps0ef4df8b.jpg (http://s34.photobucket.com/user/82boy/media/IMG_0641pointmarked_zps0ef4df8b.jpg.html)

[beartooth91]

Ok, that I see!
However, I do not recall seeing any of these on my experiments, today. That said; I had a circular ring of scoring, around the bullet, probably right around or just behind where your marks are. (Of course, yours is a different cartridge and probably different bullet.)
And the width of the scoring ring is about the width of your mark, getting thinner and broken as I seated in more.

[Smokey262]

When i use that depth checking method I use a sharpie to make the bullet black. It makes it easier for me to see the marks.

[thermaler]

Maybe your chamber has a long freebore before engaging the lands--that might explain the lack of markings where the rifling begins?

[82boy]

Ok, that I see!
However, I do not recall seeing any of these on my experiments, today. That said; I had a circular ring of scoring, around the bullet, probably right around or just behind where your marks are. (Of course, yours is a different cartridge and probably different bullet.)
And the width of the scoring ring is about the width of your mark, getting thinner and broken as I seated in more.

The cartridge and bullet has nothing to do with this. The marks are easier to see on longer VLD bullets. The circular mark you are seeing is more than likely caused by you comparator tool. You need to polish the bullet with 0000 steel wool, each and every time you place the bullet into the chamber. Or you can blacken the bullet with a sharpie, or use a match and soot it up, to help make the marks more visible.