We've had a lot of questions come in regarding possible new ammunition recommendations in response to the updated barrel design. The overall list of recommended ammunition hasn't really changed, however there is something we feel is worth noting.
After extensive testing with various ammunition we have concluded that all remaining key-holing issues have been isolated to one particular brand and weight of ammunition. Unfortunately this seems to be the most common and available ammunition: CCI Maxi-Mag 40gr.
The 30gr and 50gr varieties of CCI shoot flawlessly, as do other brands of 30gr., 40gr., and 50gr. ammunition. For some reason, though, it seems that the 40gr. CCI Maxi-Mag in particular still has sporadic key-holing. At this point in time we have deemed it ammunition specific and recommend trying a different grain or brand of ammunition if your PMR-30 is still continuing to key-hole with an updated barrel.
This in no way means that all of your CCI Maxi-Mag 40gr. will key-hole; it just means we have experienced occasional key-holing with that particular ammunition and feel we should make everyone aware of it in the event you experience the same thing we have.
We'll be sure to keep you updated if we find out anything more!
As it stands, continue to steer clear of non-USA manufactured .22WMR rounds as they have a higher risk of case-rupturing due to inferior quality.