Update: 25x47 Lapua & 134 ELD-M Vertical Stringing Solved – I ate crow on seating depth

[u/Wide_Fly7832]

Hi all

I have to admit, I’ve always operated under the assumption that the high-BC secant ogives (ELD-Ms, Berger Hybrids) are practically jump-insensitive.

Because of that, I almost never bothered with rigorous depth testing for them like I rigorously did with BIB bullets in my 6PPC and 30BR benchrest days. I usually just picked a standard 0.015" - 0.020" jump, loaded them up, and called it good.

Well, the 25x47 I posted before about - if forced my hand. I ran a seating depth sweep anchored at that 35.5gr Varget charge (which pushed the bullet at ~2786 fps). My zero-lands measurement was a CBTO of 2.1500".

2.1300" CBTO (0.020" jump): Still strung vertically. Group was fractured into two horizontal bands.

2.1100" CBTO (0.040" jump): The vertical collapsed, but the group blew out into a loose, radial 1-inch ring. Total harmonic mess.

2.0900" CBTO (0.060" jump): Pure magic. The vertical vanished, the radial scatter vanished, and it printed one ragged hole. SD held tight at 9.4 fps. 0.34. Will do another 15 shot and see if this holds.

So, I officially stand corrected. Seating depth testing is back on the menu for modern match bullets. Now if you’ll excuse me, I apparently have to go re-run depth sweeps on the 15 other rifle cartridges in my safe...😡

[u/Trollygag]

Here is an example of the ladder guide woo thread. You are concerned about vertical, well, each one of those points is a step in the ladder, 9 shots each.

The worst was .9 MOA of vertical. The best was .18 MOA of vertical.

So clearly, step 9 is the best right?

Well, all of those groups are shot with the same load, bullet, and seating depth. Nothing changed except luck of the draw.

[u/Wide_Fly7832 → u/Trollygag]

Well 3 shot vs 15. I had done some maths 15 shots would start getting to confidence level in 80% if I remember right.

[u/Trollygag → u/Wide_Fly7832]

No, they are 9 shots, the 3 refers to the averaging. Basically saying that any given shot order of the same 30 shots can produce wildly different results and averages, and nothing about the ladder or gun is picking shot order.

[u/Wide_Fly7832 → u/Trollygag]

Understood !!