I seem to be getting some keyholing with my 147gr loads too.
Zero 147gr JHP
Speer once fired brass
I haven't investigated further with the load. Just got married and was shooting in the GA State match this past weekend. I'm not liking the fact that I may have to rebarrel the gun to get rid of the issue though. = I have two M&P 9mm pistols set up for USPSA Production and wanted to shoot a 147gr load for the soft recoil benefits. I've shot up all my Zero 115gr JPH loads I worked up over Titegroup 4.7gr. Those thigns were dead on accurate but to damn snappy for me.
Keyholing 147 Zero's are not rare. I think a couple of years ago they changed something and where they used to shoot great in my CZ they started going sideways. At the same time 2 other people noticed the same problem (one of them USPSA Production GM). I switched heads and the problem went away. Ever since then I keep on hearing people having problems with Zero's so I never had a need to go back and with their current prices I would be mad to go back. On the other hand, pleanty of guns shoot them fine. I think their design plays well with some barrels and really badly with others.
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