Determining bullet seating depth

[Alan W]

I am fairly new to reloading and have only reloaded for a 30-30 lever action. I recently purchased a bolt action rifle in .223. As I have never used a bolt action rifle before I put together five cartridges with no primer or powder to cycle the action and get familiar with it. The load I intend to use calls for an over all length of 2.2” so I used that and measured it with my calipers. I recently purchased a means to measure base to ogive, so I measured that at 1.88” figuring out how to use it. When I cycled the cartridges thru the action, the bolt felt a little tight closing. I cycled three cartridges and then measured the base to ogive because I realized I might be pushing the bullet into the rifling. Now the base to ogive measures 1.85” on all three cartridges. I then cycled these cartridges thru the rifle a few times and the measurement did not change. Would this be an accurate measurement for my base to the rifling for this particular bullet?

 

[tightgroup tiger]

Would this be an accurate measurement for my base to the rifling for this particular bullet?

No, it wouldn't.
Your 1.88" OAL loads may have been right on the edge of being that measurement you seek. But you reduced your OAL by .030" in one jump and now it fits. It could be the distance in your rifle from the base to the rifling may be 1.878" and now your grossly short.
If you could close your bolt on 1.88" without a lot of effort, you should have been farely close there. You should have reduced at about .005" at a time until you found no resistance, then creep back up until you feel it again.
Or get the appropriate gages and tools to pinpoint it.
Some rifles shoot most accurately at a gap of around .020" and some shoot best at sitting right at the riflings. Some, somewhere in between.

 

[mrawesome22-250]

Take a sized case and cut a slit vertically down the center of the neck, just into the shoulder. Now barely seat a bullet by hand in the case. Slide this into the chamber and close the bolt. Eject and take a measurement. This bullets ogive is touching the rifling. Back off .020" and start load work ups.

Edit: After ejection, pull the bullet out of the case, barely reseat, and close the bolt on it again. Repeat 3 or 4 times to make sure you are getting a consistent measurement.

 

[Hooda Thunkit]

^^^^
That is exactly how I do it. Never failed me yet.

 

[entropy]

On the rare occasion I do so, that is the method I was taught also.

 

[sequins]

You can buy a hornady tool that does the same for a few bucks, too.