Locating Bullet Touch Point in Barrel With Bolt?

[ole-has-been]

Regardless of the weight or length of a bullet, shouldn't the jam point be the same for each bullet (of that caliber)?

Once I locate the jam of a .204 40gr Vmax, measuring base to ogive, won't that be the same for a .204 32gr Vmax or a .204 55gr Berger BT varmint, etc.

The method I'm using in locating the jam is seating a bullet long in a case, lubing the ogive and closing the bolt. I do this with 3 cases of the same bullet.

The reason for the question, is that I get different results, with different bullets. My thinking is that I should get the same jam point every time regardless of the bullet because the ogive to base measurement should always be the same after closing the bolt, regardless how heavy or long the bullet is.

Thank you

Hope I don't step on any toes, just thought I would try and help you out a bit too.
I truly think your question is a fantastic one, and deserves a simple easy answer.
I believe by what you have seen for yourself, that the simple answer is no.
And the reason why is due to different bullet ogive profiles. Remember, you are JAMMING the bullet and some will JAM into the grooves more easily than others with the method you have chosen.
However, if you are ONLY wanting to use this measurement as a GUIDE, so as to know where the danger point is, then take about .020 off of your JAM measurement and use it as a guide to know your not gonna seat into the lands. Again, as a guide only. All reloading procedures should be double checked before wiping your hands and calling it done.
I thank you for posting this question and admire your reasons for asking it sir.
God speed

 

[master_photog]

Hope I don't step on any toes, just thought I would try and help you out a bit too.
I truly think your question is a fantastic one, and deserves a simple easy answer.
I believe by what you have seen for yourself, that the simple answer is no.
And the reason why is due to different bullet ogive profiles. Remember, you are JAMMING the bullet and some will JAM into the grooves more easily than others with the method you have chosen.
However, if you are ONLY wanting to use this measurement as a GUIDE, so as to know where the danger point is, then take about .020 off of your JAM measurement and use it as a guide to know your not gonna seat into the lands. Again, as a guide only. All reloading procedures should be double checked before wiping your hands and calling it done.
I thank you for posting this question and admire your reasons for asking it sir.
God speed

Many thanks for your reply, this is very consistent with what others have said. You all have confirmed my ignorance of assuming that the ogive of each bullet, of the same caliber, meets the jam point at exactly the same place (when using the bolt closing method as I've described).

 

[cw308]

Some of my benchrest shooter friends that jam their rounds do something called " Soft Seat" . Using bushing dies, the neck tension is set light , bullet is seated long and when chambered it will seat itself to the lands . Problem is the bullet will stay in place and the case and powder will follow your bolt . So fire every round when chambered.
I found the stripped bolt method very accurate using the same bullet , brand and bullet lot number. Every bullet change should be checked even lot change.. Bolt closure for, bolt face to datum measurement , Bolt lift for, bolt face to ogive measurement. Case measurement will not change , Bolt face to ogive will from lands washing out. Check every 500 rounds.

 

[Coyotefurharvester]

With hunting rifles once you have a bolt face to ogive touch measurement, a comparator is useful as it will allow you to quickly acquire measurements from each of your available bullet types. Using those "measurements" for seating die set up is a whole different discussion.

 

[cw308]

Coyote
Using the measurements for both case and bullet length , just a matter of long settings and working down , alittle at a time.
Chris