The only difference is the OAL length, 2.005"-2.015" vs the 260's 2.025"-2.035". In its pure wildcat days( post 260 Rem) it was the 308 Win simply necked to 6.5/264 and fireformed without any other changes. There was also a few other improved versions with 30 and 35 shoulders. For whatever reasons when Big Green submitted the 260 specs to SAAMI they specified the longer neck length.
There were other improved versions with 30 and 35 shoulders, but the 40 has always been the de facto standard.
If you call/email Criterion they'll give you the reamer specs or email Dave @ PTG and ask him.
Bill
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