Thread: When to re optimize seating depth ?

Originally Posted by Bagheera

Are people running a new seating depth ladder from time to time ?

Do you measure distance to lands (CBTO) and retrial seating depth steps when it burns out longer ?

Would you routinely retrial for each new projectile type you change to ?

Is anyone monitoring the bullet base to ogive lengths to see if they vary from batch to batch or over years ?

Any other criteria like just every year or two ?

You should definitely re-check bullet seating depth when changing to a different type or brand of bullet, even if they are the same nominal weight, or close to it. Even bullets of the same type from the same manufacturer can vary a bit from lot to lot.
Here are some overall lengths of cartridges for a 222 which I had re-barrelled recently, measured with the bullets touching the lands at ‘finger pressure’. I won’t go into how the lengths were measured, except to say that I am quite confident of the accuracy.
50gr Hornady Z-max 54.55mm
50gr Hornady Z-max 54.75mm (different lot from above)
50gr Hornady SPSX 54.00mm
50gr Hornady V-max 54.90mm
53gr Hornady V-max 56.55mm
52gr Sierra Matchking 55.15mm

It’s easy to see that the same overall length cannot be used if the jump to the lands is to be kept the same. If, for example, all seating depths were based on the overall length obtained with the 50gr V-Max, seated, say, 0.25mm off the lands, some other projectiles would get jammed hard into the lands.

Some shooters claim that they get by far the best accuracy with the bullets jammed hard into the lands. Personally, I won’t have a bar of this. I used it a few times early in my reloading days, many decades ago, and had cause to regret it. Twice, when I was shooting on a range in competitions, emergency situations arose and the RSO bellowed ‘Cease fire. Actions open. Immediately’. I opened my action, the bullet stayed stuck in the lands, and powder spilled out and went everywhere. It took ages to find a cleaning rod to knock the jammed bullet out and clean up the mess. That sort of thing is annoying enough when it happens on a range, but in the field it would be far worse.