300WM Faster Than Expected

[Shane Lindsey]

Did you test these on fireformed cases? I trashed some ADG cases and thought I was good. Loaded the same load and was way to hot and had to back it down a bit. Case capacity matters, especially with belted mags. What you think is good, may be too much when fireformed.

 

[drabdrew]

This is almost always a sign of over pressure. The poor group sizes points there too. Adg is known to not show pressure signs at absurd rates of over pressure. The old load up in increments until you reach pressure signs is dangerous with adg brass. Your only way to do this correctly is with a reloading software.

 

[VarmintBob]

So, for those who commented on my Bone Head Mistake thread, I did not use the blended H1000/H4831SC for what I'm about to say!

Doing load development on a factory Christensen Ridgeline, after following factory break in procedure using factory Hornady 180gr Superformance ammo. I loaded up some 210gr Bergers in new ADG brass, Federal 215 LRM primers, .040" off lands, .002" neck tension, and a new 1lb can of H1000. Berger book says max load 75.5 at 2804fps, I know it's not always gonna match but it's a good average expectation.

Shooting conditions: Temperature 60⁰F, Humidity 25%, Elevation ~500', Wind 8mph WNW.

5 Shot groups, measure speed with Garmin Xerox C1

Charge Avg FPS SD ES
74.7 2894.5 8.0 22.0
74.9 2904.8 6.9 20.4
75.2 2925.1 5.3 14.8
75.5 2928.1 4.6 14.3
75.8 2938.5 17.5 49.4

All shots grouped horrible but there seems to be a decent node at 75.2 and 75.5 but those groups were 1.5"-2" though.

First I'm curious as to why my results are so much faster than book? Never had any signs of pressure but maybe a slightly sticky bolt on the 75.8 group. Was hard to tell as the action on this Christensen is a little tight naturally after a fired round. Second can I wrangle this load in by adjusting seating depth?

I know all rifles are different but I have a Bergara 300wm that loves this recipe so I used it as a starting point. With that rifle, doing seating depth tests, the worst groups were around .80"-1.0" and when I finally settled on .040" off the lands I could get .50"-.60" groups as long as I did my part with 75.8gr of H1000.

There is NO reason at all to think that a data book powder weight will give you the velocity in your rifle that is listed in that data book. You have no idea what the chamber size was in that test rifle. And if you are asking this question, I would guess you don't know the chamber size in your rifle either. Barrel friction is another big variable. The humidity of the powder when it was loaded is another variable. The one thing you CAN get from the data book is that the max velocity listed is close to max pressure when you adjust for differences in barrel length. So if 2804 fps was a MAX load, then your load is probably way over max pressure as you can see from your velocity.