Thread: Pressure Differences - ELD-M and ELD-X

Originally Posted by Rated M for Magnum

Attachment 138503

Here they are side by side, 162 ELD-M ON the left, 162 ELD-X in the middle and 175 ELD-X on the right.

How did you get on @Edunn? Have you managed to get out and shoot them yet?

Topical prompt!

Had quite an interesting experience over the weekend. On Saturday morning I loaded up one round each of the 162g ELDX from 68.5g up to 74.0g (AR2217) - obviously expecting to have to stop shooting around the 72.0g mark. COAL was 3.400", which comfortably fits in my mag (Browning X Bolt) and is 0.020" off lands.

Had faint ejector marks and flat-ish primers from 72.5 through to 74.0, but they all shot fine with no major concerns at the time. Chrono read 3115 for the 74.0g charge.

Thought I was onto a winner here, so loaded up four each of 72.5, 73.0, 73.5, and 74.0.

72.5g shot a 1" group but nothing to be excited about. Faint ejector stamp, relatively flat primer. Waited for everything to cool down, then loaded up 73.0g. First shot, noticeably more felt recoil, and bolt very sticky with a crater-like ejector stamp. Chrono showed 3144 fps. I thought it must have been a rogue load (given the day before was fine), so tried one more with exactly the same result. The tough pill to swallow is both rounds went through the same hole but far too much pressure to use that load safely.

I didn't shoot any more (obviously) and went on to validate my 7mm08 bushpig out to 300, which went really well and saved the day.

Did a lot of thinking about why the difference between the two days last night have come to the conclusion that:

1) Charges were accurate, as I weighed the leftover rounds
2) Sunday was slightly warmer and sunnier than Saturday. But realistically, I'm in Dunedin, so was only a one/two degree difference.
3) I should have paid more attention to the velocities the day before - on review, there was a flat-ish velocity node from 70.5 through to 72.0, then a jump of 97fps from 72.0 to 72.5. Probably indicating that I was hitting pressure around that 72g mark even though there were only very light symptoms. I guess this means that any small changes in conditions could cause a pressure spike? That segues on to my final finding:
4) For some outrageous and unknown reason, I had loaded everything at 3.400" COAL on Saturday and 3.990" on Sunday. I only clicked to that last night when I was re-weighing and re-measuring everything - moral of that story, is have everything written down right in front of me all the time - I follow recipes for a living (scientist) so should have bloody known better than to do it off the top of my head.

So the plan, now, is to load up four of each from 70.5 through to 72.0 in half grain increments and try again.

Very happy to hear everyone's thoughts, laughs, tut-tut-tutting, and somewhat solicited advice.

Cheers,
Elliott