As I noted, it's not advisable to use the C&S firing pin until you've reduced the power of the mainspring. When I saw those cracked primers with my 610 using this firing pin I feared it might lead to a pierced primer, thus my warning. I would suggest that you either order the factory firing pin and hope you get one with a .495 inch length or start backing off on the power of the mainspring by either filing down the strain screw or shimming it out. I prefer shimming because it's easy to reverse.
If you have a Dremel and access to some small diamond burrs with a 1/8 inch shank it's not very difficult to make up shims to fit under the head of the strain screw. BTW, you can get these burrs from MSC industrial supply via the following link. You'll also need some shim stock which you should be able to find at the same source, I would suggest ordering 0.005 and 0.010 inch stock. Finally, you'll want a 0.147 inch diameter drill for the ID size, can't remember the number of this size but it's a standard number drill.
MSC Item Detail
To make the shims you'll need a 0.147 inch ID and a finished outside diameter of 0.218 inch. Start out by drilling the shim stock, deburr the drilled holes, and then use some scissors to cut them close to size. Then use the diamond burr in a Dremel to shape them to the final OD. Once you have them made you'll have to pay attention to getting the shim dropped into the counterbore in the frame or the screw head may catch the shim. I'd suggest you start out with just 0.010 inch of shim and test it's effect. Then you can continue to add shims until you get to the point where misfires become a problem. Once there remove 0.005 inch of shim and you'll probably find you are good. Ideally you want to use a good trigger gage for this testing but it's not an absolute essential. If you already have a good trigger gage, shim the strain screw to produce a 9.5 lbs trigger pull and work it down from there.
A bit of good news is that if you spend the time you'll end up with a lighter trigger and 100% reliability for ignition. If you want to go all out, order a 14 lbs. rebound spring, an installation tool and an 800 grit stone to do a bit of smoothing on the rebound slide and the DA sear surface on the trigger. I don't know exactly why but I've found the N frames to be the easiest of all the S&W's to get a really perfect trigger with. I have a hunch that it's the stop rod in the rebound spring but haven't confirmed that yet. One of these days I'll order one and fit it into my 620 because there is still a very tiny "hitch" in the trigger pull that may be the rebound spring buckling and binding. BTW, pay VERY CLOSE attention to the orientation of that stop rod when you remove it, install it backwards and it will lock the trigger up solid when the gun is oriented "wrong".
I'll also repeat that you want to examine the primers on every single fired casing, they will tell you if you are hitting the primers too hard. BTW, that was darned good thinking on getting that stuck firing pin free.
