Hi -
Shortly after I bought my DR500M, I contacted Epiphone to find out what strings are installed from the factory. Here's the reply I received,
Regards
"Sorry about the confusion! All Masterbilt steel-string guitars come from the factory with Gibson Masterbuilt .012-.052. It will not void your warranty to use medium-guage strings, it will just require the appropriate neck adjustments to accommodate for the increased neck tension. I hope this information is helpful! Thanks for the inquiry!"
Best regards,
Benton Cummings
Gibson Customer Service
1-800-4GIBSON
service@gibson.com