Improving ES in 300 WM is it just powder selection

Interesting so switching to a non magnum primer improved your ES, was there any velocity change?
The magnum primers were not around when the 300WM was developed, the standards primers is what that round was designed for in the beginning. The powders have come along way also since the 60's.
For what it's worth, my gun really likes IMR 4350 as far as accuracy is concerned, but I prefer the H1000 for the temperature stability.
 
Yes, if you can believe it my velocity went up 20fps. It was crazy. Verified the test over 20-30 rounds to make sure it wasn't a fluke

I don't find that amazing at all. Velocity is a function of the pressure curve (among other things). A magnum primer creates a hotter initial burn but in a large case, the pressure could drop off at the final burn. Ideally, the pressure rises evenly and smoothly throughout the burn giving rise to maximum velocity as the bullet exits the bore. If you just try to imagine a pressure spike earlier in the burn when the bullet isn't even going that fast yet and a subsequent lower pressure at exit, you can easily see why a magnum primer might not produce as high a velocity as the standard primer in all cases. It's somewhat the same as the way that faster powders don't necessarily produce the highest velocity. Try plugging your data into an internal ballistics program like quickload, but make sure you read the documentation to learn how to play with primer types. It's a fun and very informative way to play with loads.
 
Been banging my head on the wall trying to improve the ES and SD on my 300 WM.
All brass prepared and trimmed properly,full length sized, mandrel sized necks, primed with federal LRM primers, all charges weighed on digital and 10-10 scale and were as perfect to the tenth of a grain as I could get them, bullets seated on lee die and all measured to ogive for OAL very consistent lengths. All cases water checked and all were with 1 grn of each between the highest and lowest capacity cases (the deviated shots for high or low extreme spread weren't in the cases with 1 grn off volume). All measured for concentricity and worst was .005 on bullet near tip, the concentricity again didnt seem to be the ones that were low or high on ES.
Tried h4350 with some barnes 180 ttsx and accuracy was horrible however just likely needed OAL adjusted, did the 10 shot method goin .2 at a time after working up safely of course and picked best node and the 5 and 10 shot ES and SD was bad tried a few other charges right in that charge area flat spot. ES was around 60 and SD around 20
Wanting more precision I also tried H414 (didn't wanna burn up the 4350) and some Hornady 168 match, same prep and load workup ES around 70 on a ten shot group after getting the best place on node and SD right around 20. These were accurate at 100 yards even without adjusting OAL

So my question is to really lower those numbers should i look back to my process or more to the powder?


Powder, Neck tension & Primers!
 
Try CCI-250's as well, I shoot rl26 in my 300 wm with 215gr hybrids and I got significantly better SD/ES with CCI vs the Federal 215m.

I had the same discovery with my 7 SAUM and using Federal 210m primers over a magnum primer, both with H1000 and RL26.

*I have several shooting buddies who have had the exact same discovery. Most of us don't use the 215m primer unless it's in the really big magnum's - Ultra mags, Normas and Lapua.
 
I agree with trying H1000 instead, but I had another question. Do you get your brass squeaky clean before loading? In particular, is the inside of the neck VERY clran?
I lubed neck lightly for mandrel sizing withlee case lube. When trimming i use a qtip with alcohol on each neck to remove lube etc
 
Try CCI-250's as well, I shoot rl26 in my 300 wm with 215gr hybrids and I got significantly better SD/ES with CCI vs the Federal 215m.

I had the same discovery with my 7 SAUM and using Federal 210m primers over a magnum primer, both with H1000 and RL26.

*I have several shooting buddies who have had the exact same discovery. Most of us don't use the 215m primer unless it's in the really big magnum's - Ultra mags, Normas and Lapua.
Your the second to suggest non magnum primers, Im gonna try it for sure, im down to the last few magnum primers anyways
 
I lubed neck lightly for mandrel sizing withlee case lube. When trimming i use a qtip with alcohol on each neck to remove lube etc
Do you do any case cleaning before resizing and then expanding?
Getting the inside of the neck extra clean could be causing some problems. Try an experiment where you don't wipe out the inside of the neck . Just leave the lube you used for neck expanding in there. I like to use Redding Dry Neck Lube for the inside of the neck before running the neck over the expander mandrel.
 
TBH i just seated same depth as similar factory ammo for testing purposes, was tryingto tune ES and SD before adjusting seating
You might see some improvements in your ES and SD with different seating depths. Not sure where you are at now, but play around with jumping in increments of .015" or .020" with 5 rounds per depth and you might find a place where your pressures/velocity are more consistent.
 
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