Ruger 10-.17 HMII

[Joe's]

I recently picked up a SS 10-22 chambered in .22 LR. Would like to install a SS H.W. Hart barrel that I also got awhile ago. It is chambered in .17 HMII.
On the .17 barrel it is stamped "Use With Heavy Bolt". How do I tell if it already has one and if it doesn't where can I get one.

Thanks for your help,
Joe's