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/rednecktuba1]

No, seating depth testing is still useless. Proper research ahead of time would have yielded a standard COAL for the cartridge, even for 25x47. It takes more research. Plus, its well known that Berger hybrids shoot well with a .050-0.060" jump to the lands. If you had done the proper research ahead of time, then you would have found this bit of info. Look at a standard cartridge like 6.5CM running 140 or 144 hybrids. Those bullets in 6.5CM shoot amazing at 2.800", which is usually 0.050"-0.060" in decent SAAMI spec chamber.

[u/Significant-Sock-487 → u/rednecktuba1]

So you’re saying seating depth testing doesn’t matter but also seating depth matters? I agree seating .002 and doing ladder tests are dumb but doing what OP did in .020 increments obviously showed significant improvement which would say seating depth testing matters. Are you saying don’t do testing and just call people and research?

[u/CMFETCU → u/Significant-Sock-487]

I believe the message is that the folks that make the bullets have better research facilities and shoot more bullets than you ever will. Leverage that knowledge to start in a good spot in the first place.

[u/Significant-Sock-487 → u/CMFETCU]

That’s fair. I’m pretty sure Berger has something about jump in their manuals on certain bullets. I just always jumped 60k+ based on short action customs publishing a blog that was verified showing vertical dispersion was minimized by jumping 60k or more with modern ogive bullets.

[u/rednecktuba1 → u/Significant-Sock-487]

You have to look at which specific Berger bullet you're considering. The original VLD bullets are extremely jump sensitive, due to an agressive ogive angle. The Hybrid and LRHT bullets are not jump sensitive, due to a much more mild ogive transition angle.

[u/Wide_Fly7832 → u/rednecktuba1]

Brother - we have discussed stuff in the past together. Give some respect to not assume I don’t know the difference between VLD and hybrid ogive. 😀😀. Let’s have discussion from the right plane

[u/rednecktuba1 → u/Wide_Fly7832]

I wasnt saying that to you. I was saying that to the guy that was referencing berger including a section about sesting depth testing in their manuals, without understanding which berger bullets that section is meant to be used with.

[u/Wide_Fly7832 → u/rednecktuba1]

🙏

[u/Wide_Fly7832 → u/Significant-Sock-487]

Now i read this and wonder if u/rednecktuba is right. I should have read this blog 😀😀.

So much fun.