This has me scratching my head.
 

So if the 7 PRC uses the 375 ruger as its parent cartridge then why does RCBS list different shell holders for the two cartridges??
#4 for the 375ruger and #38 for the 7 PRC. :thinking-006:

Same story with the 6.5 PRC.
I've been using a #4.

I looked up Hornady and their chart shows the 375 and 7PRC using the same number.
Not sure what's up with RCBS.

The #4 works with Hornady cases, but it won't work with ADG cases.

#4 seems to work on Peterson brass just fine.

I have Hornady, Peterson and ADG brass. Both the number 4 and 38 fit all three. The only difference I can measure is the number 4 is about three thousandths smaller in the groove area.

My ADG brass is actually stamped Gunwerks. The #4 will not fit over the rim.