Mag rifle vs match grade primers

[GMHVAC]

I'm surprised nobody asked about ambient temperature between the Labradar experiences. Unless you're using a temp stable powder like Varget, 100 fps differences are very common with ambient temp changes. I've seen larger spans between winter and summer.

All my tests were done literally within the same hour. It was a cloudy day where the sun would peek out every 15 min or so. No change in ambient. And the powder was H1000. Temp stable powder.

 

[Dake21]

Makes sense to me, 100 fps difference by just changing the primer sounds too much. Since op is not sure of his charge weight I suppose we will never know what really happened that day.