CCI primers are not harder. they are the thinnest srp made. They work almost perfect in 9mm. Some guns with high usage and wheel guns with lighter springs have a hard time as they don't put out enough force to lite them off.
And before someone post the link from the sksboard. cci changed the compound in the spm primer so they are not the same as the srp anymore. But they are completely safe to use in place of a spp.
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