Playing with seating depth?

[Tim]

For a given bullet, is it worth it to play with seating depth before settling on a charge weight?

I'm loading 6.5CM using 140gr ELD-M bullets. This same bullet in Hornady's factory Match ammo measures right at 2.200" (base to ogive).

Using an OAL gauge, I'm getting a measurement on my rifle of 2.234" to the rifling.

I have 50 rounds of various charge weights ready to go for testing, all loaded to 2.200"

Should I finish my ladder tests, settle on a load and then refine with OAL adjustments? Or should I start over and load to something like 2.225"?

Goal is long range (>800 yards) precision.

ETA: This is a bolt gun, not an auto loader.

 

[Djstorm100]

Bullet seating is fine tuning...have a consistent load (ES/SD are the nearly the same) but the groups are open up just a little than you like. I had a rifle that went to .4moa to .29moa (10 shot groups) just by changing seating depth. I always start out at 0.020 off the lands and move back in 0.005 steps.

charge weight first...then bullet seating depth.

Look at all the loads and then at 42.3 notice how there is little veritcal displacement vs the others? Key load..it also had the lowest SD/ES in the work up. Had a large node of 42.1-42.3.

Then moved to bullet seating testing.. I was cold and sick but determined to get this load finish for a match in 2 weeks. First group was sighters..then .020, 0.025, 0.030, 0.035 and so forth.

0.035 is final group.

 

[Charlie R]

I agree with you, 0.034 certainly seems like a big jump for a relatively long bullet, based on all I have heard and read. Everyone says touching, to just off of the lands, by about 0.002 for VLD type bullets.

Seating depth is fine tuning as DJStorm100 says. I have gotten to where I hate traditional ladder tests consisting of 50+ rounds. Takes all day to shoot it, allows a ton of opportunity for operator influence (read error), and is expensive. I have gone to the 10 round ladder test using a chronograph to zero in on the charge weight ranges that are most consistent in terms of speed (vertical deviation) and then I go back and run a 3 (usually) or 5 shot ladder within that range. Once I know the two best charges, I would go in between or towards the most accurate if they are not the same, and then play with seating depth.

Having said all of that bullet jump remains proverbial "black box", the sausage making, the Gordian Knot of precision reloading. It all makes sense until one encounters "the exception that proves the rule". But it is logical to eliminate the variables with the greatest influence on point of impact first before proceeding to those of lesser significance.

 

[Tim]

I have gotten to where I hate traditional ladder tests consisting of 50+ rounds.

I should add that this is round 2 of load development. I've already narrowed down to a 1g +\- and am testing 10 round batches within that specific range.