I guess that I should post their website, too:
As delivered from the factory, SKSs come with a floating firing pin. This can cause the gun to sometimes "Machine gun" or "slam fire." This can be a dangerous situation if you are not expecting it. So Murray has made replacement springs for the SKS that avoids this problem. These new parts are "drop in" and can be done quickly and easily. Every SKS should be fitted with these new replacement parts to make these wonderful guns as safe as possible.
This “New For 2007” replacement firing pin is designed after the original Russian design. And, it fits all SKS’s. Even pre-51 versions. But, with pre-51 versions you need a different spring. This is due to the hole in the bolt being drilled deeper in “later” versions. This new firing pin eliminates slam-fire and uncontrollable full-auto incidents! And, allows use of “soft primered “American” ammo, or reloads.
Seen below are Murray's NEW SS SKS Firing Pins, Firing Pin with spring for pre-'51 Russians - (center) Firing pin with spring for EVERYTHING else (top).
“Original” Russian style, newly manufactured, CNC machined and heat-treated 420 SS firing pin and “Wolff” spring are now available. Drop in fit with no alterations required. Fits early Russian, (with special shorter spring) later Russian, Chinese, Yugoslavian, Albanian, and Romanians. $37.00 includes “First Class” anywhere in the U.S. and Canada. (credit card - $39.00) [Texas residents add 6.25% tax]
"Kit" includes firing pin, spring, extra spring, written instructions and a picture to aid in installation.
And Now...NEW FOR 2013
We offer the same FP's as above except for a slight "head" design change and a lower heat treat factor. Pictured below is the version that is still 100% drop-in installation. (Item #001)
And to have the most bulletproof version we make, we offer our new Item #001M, pictured below, which requires a very small modification to your carrier. So if you are sending your bolt for FP Kit Installation, send the Carrier too, and we can machine it for this "best" version. Even with the modification, you could still go back to an original FP, should you choose to do so.