I had this same situation happen to me just this week. My smith worked up a load using 89 grains Retumbo with Berger 210 VLD's and Federal 215 primers. He shot a group of .415 off a portable bench on a somewhat windy morning. I didn't have any regular 215 primers so I used some 215 Match that I had bought just for this rifle thinking along the same lines as you. The 215M did not work out well at all compared to the the standard 215's he was using. My groups opened way up. In fact it is incredible to me how much my results parallel the results you just mentioned. Makes me feel a little bit better actually because I haven't been able to get back out to the range to test the new loads with the 215 standard primers. From my research the 215 Match primers are a fair bit hotter.
I would recommend trying to find some more 215's and load them before starting down the road of changing your powder weights. It may just be that you need to use that primer in that rifle with that powder.
Here is a test done by a fellow using a home made device and his results when testing the strength and consistency of different primers.
Primer Testing Reference