I think your gunsmith may be on the right track. A "controlled feed" action like the Ruger usually holds the case head tightly enough against the bolt face to ignite the primer even if the headspace is grossly excessive. Your experience with the single misfire may be a once-in-a-lifetime happenstance with this gun or with the Speer ammunition, but installing a stonger firing pin spring can't hurt anything.

I find it a little unusual that a "gunsmith" would just change the firing pin spring and not check the headspace and the belt dimensions of the factory ammo as well.



Is he going to fire off a hundred rounds of various factory rounds now to test it? If this site had not changed servers I would post the address to John Ricks post on belted cartridge headspace. The easiest way to find it now is with the search function as I mentioned above.



A stronger than required firing pin spring can increase bolt lift and also make the safety difficult to work and make it noisy as well.



SBT,



Explain what you mean when you said the gunsmith was able to "cock it by hand". Did he pull the firing pin back with his fingers??

I still stand by my first thought that you didn't have the rifle 100% into battery. I tried it again on my Ruger 77 and if the bolt handle is up a small amount, mainspring energy is absorbed to complete the bolt closure therefore resulting in a light firing pin hit on the primer. It is possible that it was user malfunction instead of Ruger malfunction. That's just my $.01 worth. ...Roger.