Advise on my .300 win mag load

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I am using norma brass, h1000 powder, federal 215m primers, and berger 230 hybrid target bullets. I fireformed brass, uniformed primer pockets, deburred flash holes, trimmed and chamfered to uniform length. I tested 72-75 grain loads .040" jump in half grain increments. 75 grains just barely showed ejector marks and 74.5 and 75 showed huge extreme spread like 80-100 fps making me believe 74.5 is getting a little hot. I posted a thread a couple days about my primers not seating flush. (Even called brownells and still no answer) So this could be a cause of higher than normal extreme spread. So today I tested 73.4, 73.7, and 74.0 grains and .040" and .090" jump. Here are the results:

Seating Depth: Powder Charge: CTC: Velocity: 1: 2: 3:

.040" 73.4 .256" 2567 2466 2478
.040" 73.7 .118" 2721 2732 2744
.040" 74.0 1.192" 2840 2822 2838
.090" 73.4 1.002 " 2589 2629 2642
.090" 73.7 1.026" 2785 2800 2739
.090" 74.0 .587" 2836 2826 2842

These were all shot from 100 yards 3 shot groups in the order listed. Once I got to .040" 74.0 grains the mirage was real bad and I was chasing that little dot around probably explaining how they opened up so much after that. Some of these ES are horrible and even the best ones are barely acceptable. Yes I know 3 shots isnt really a good representation of ES of a load. Like I was saying earlier, my primers are not sitting all the way flush for some reason. Could this explain it? Or is my chrono giving false readings. I find it funny how from 73.4 grains to 73.7 grains there is a 229 fps increase.

So 4/6 of my loads where shot in horrible mirage bringing sub 1/4 moa groups to over 1" and my chrono is more than likely no working right. where do I go from here? Is it safe to say .040" and 73.7 grains is a load worth loading some up of and trying out farther? Or do I need to redo this test for accuracy and forget about the chrono?

700 action
brouton 9 twist #8 contour 28"
badger thruster break
mcmillan a5
ptg tactical bottom metal
badger rings/ base
nightforce 5.5-22x50

Shooting off sandbags. Let me know if there is any other information needed to solve this puzzle.

Thanks
Zack

 

[Greyfox]

I ordered Norma brass from Brownells a few months ago and found the same issue with 215's. I could not seat them using my Redding hand primer tool. Since I had issues with this seater in the past I ended up using my Forster Coaxial primer seater and this pushed them home without deformation. There is a narrower dimension(tighter)at the base of the primer pocket that seems to be the issue. The Forster has a lot of leverage and a variable stroke. I can feel the resistance at the end of the stroke. Since my groups and ES are very good, I have kept using the brass and I'm up to about 7 reloads with an annealing at four reloads. Except for the tight pockets, I really like this brass. For what they charge for it, it should be perfect though. I had very small groups with 75,5 gr. H1000 with 210 VLDs, but terrible ES, 50+FPS. I tried everything, seating depth, charge, brass, etc. No improvement. I thought it was my chronograph as well, but I also tested the loads on two other chronos and there was no change. I ended up switching to 79 gr of Retumbo. This got me the same accuracy, but ES under 10FPS, very consistently. Also picked up another 100FPS with no pressure signs. Lots of shooters swear by H1000 but I guess my rifle doesn't like it.

 

[jasent]

fwiw most chrono's have an error rating of +/- 5% personally id do more testing with the 73.7