Thread: Seating Depth, Harmonics, and Accuracy

Originally Posted by Bos

Just an observation from a few weeks ago; I noticed that 2 separate seating depths gave the same sort of accuracy with a 5 shot group. Both a 20 thou and then a 40 thou jump produced the same tight groupings. Now I can understand how this might happen through the harmonic flex of a barrel, but wondering if anyone else has experienced this

Did a 30 thou or 50 thou jump give the same grouping.

For my target rifles - using Lapua and Berger projectiles - jump make little noticeable difference to the grouping.
For example:
One of my rifles has fired over 6500 rounds.
I have not adjusted the seating depth since the first load was worked up for that rifle.
With throat erosion the seating depth has steadily increased.
The rifle groups as well today as it did when it was first run in.

It may be that the load & projectile is a very forgiving combination.
It also shoots well in my other 2 target rifles for which it wasn't developed.

I've also had the same result with different powder loads for the same projectile and rifle combination.
Two loads, 2.3 grains apart that group as well as each other.

In my experience the barrel, action, projectile combination determine the results.
Some are very forgiving, grouping over a wide range, some aren't, some are very fussy.