300-NM w/ 225-ELDM's and Retumbo (or MagPro)

[rustyinbend]

Just curious if there's anyone out there using this combination specifically, and if so, what's your load data look like for either of these powders. I've run the numbers in Quickload but would love some real-world data before I start loading for my new 300-NM rifle (MPA with 27" barrel).

 

[disky1]

Doing this with h1000.
83.7g 3015fps.
ES 7
This is a few grains hotter than the hornady manual.

Had a buddy doing it with retumbo around 86.

Either way. Shooting laser beams. And nice small groups

 

[rustyinbend]

Doing this with h1000.
83.7g 3015fps.
ES 7
This is a few grains hotter than the hornady manual.

Had a buddy doing it with retumbo around 86.

Either way. Shooting laser beams. And nice small groups

Thanks ... based on QuickLoad and some other data points, I'm going to start at 84.6 grains of Retumbo, and build a 5-shot ladder at .5 increments to 86.6 ... and watch velocities and pressure signs. Your buddy ("around 86") is right in the wheelhouse of where I was thinking of aiming. If I can get to 86.6 and around 3000-ish ft/sec ... that's where I'll build a more detailed ladder and hunt for a velocity node. Only downside is that I'll be starting with brand new virgin brass (Lapua), so whatever I learn will have to be rechecked with fireformed brass. Some probably will say "Don't do any load development on new brass" ... but I refuse to totally waste all those supplies. I'm sure I'll learn "something" from the new brass.

 

[disky1]

I agree with you. But im actually doing some loading right now. My factory brass was .010 under what the headspace of once fired lapua is. I also find that although they anneal it from factory. The neck tension is all over. You can feel it sometimes. But definatly can measure it. I use a whidden seater die and the die of course doesnt move but some of the tighter feeling seating will move up to .003 on the ogive while seating.

 

[Jb343434]

Norma mag my bad: