I have what seems like a good load developed using 178 ELDM bullets with TS 15.5 in Lapua brass but I'm experiencing odd fliers. SD is ~10 fps over a large number of loads and velocity is averaging 2590 fps. On average, out of 4 shot groups (odd number but it's how many my internal mag holds so thats usually what I do with this rifle) I'll have 3 making up a 2/3 MOA (or less) group and the other shot is 1.5 to 2 inches away. Sometimes this is 2 of 4 touching, sometimes is just a good group for all 4 shots. This rifle will generally shoot just under 1 MOA groups with a good load: no match rifle but fliers are not the norm. However, it is a bit picky of a barrel: not all projectiles shoot well in it.
I'm inclined to chock it up to one (or more) of a the following causes:
- These are pandemic projectiles so perhaps I may have a not-so-good batch.
- My jump maybe in a sensitive spot (only tried one jump so far), although I do check the CBTO on all rounds and they're quite consistant showing a variance of about 1 to 1.5 thousandths.
- These are just not a good bullet for this picky barrel.
I'm interested to know what more experienced people think. Thanks in advance.
I thought of a few more items:
1. Are all bullets concentric ? Are you using a VLD seating stem? Are you possibly knocking some of them out when loading them into the magazine, or are they getting knocked out going from the magazine to the chamber?
2. As others have mentioned, I too have/have had guns that would not shoot certain bullets. I have a model 700 '06, with a 20" barrel that will only shoot Barnes TTSX bullets with a .133 jump. I have never jumped bullets that far. I also had an old .300 Weatherby that would not shoot boat tail bullets, supposedly because of the huge free bore, and would only shoot Speer flat backs, or Nosler partition bullets.
3. I remember someone at one of the bullet manufacturer's telling me that when he load developed, he kept his powder charge constant and varied the seating depth, but I don't remember how he decided on where to start with the powder. Either way, they are dependent variables that either, when changed, alter case volume, pressure, and Vo.
You might want to try the Berger recommendation, and do 10, 50, 90,
and 130 jumps. 2 different 3 shot groups of each. I am working on this with my RUM and have found some interesting stuff, but I'm not done yet.