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S&W Model 617 (22 rimfire) fail to fire fix

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EDNY:
I recently fabricated a firing pin that has eliminated the condition of Fail to Fire (FTF) inherent with the Smith and Wesson Model 617 22 Rim fire revolver.  A search of the Internet will reveal several reports by 617 owners experiencing the FTF condition.  Some of the fixes noted include, replacing the hammer, replacing the firing pin with a longer one, correcting timing, replacing springs, forcing cone issues, buying various manufactured ammo etc.

After some research and studying the condition with my Model 617-4 and 617-6 revolvers I modified a Power Custom extended firing pin with the result of 100% ignition in the revolvers.

Attachment A:  This is the actual strike impression made with my 617 revolver prior to installing my modified firing pin. FYI: It took (2) strikes before the Eley rim fire round would ignite.  Note that the strike is positioned at the very outside edge of the rim fire round.

Attachment B: The Eley drawing indicates where the firing strike should occur. Notice that it is inside the perimeter of the rim fire round and not on the rim as with my 617 revolver (Attachment A)

Attachment C:  This Eley drawing demonstrates how a properly shaped firing pin nose begins the primer crush inside and below the outer rim. The 617 firing strikes put full force on the densest outer area of the rim cartridge which prevents proper primer crush resulting in the FTF condition.  It's not uncommon to continue to FTF even after several repeat strikes in the same area.

Attachment D:  This drawing is not to scale it is intended to demonstrate the areas and angle where I removed metal from a Power Custom extended firing pin.  You will note that the firing pin nose no longer has convex shape (ball end) but rather flat face and angled upper portion.*  I also removed the rear saddle depression to ensure full unhampered forward travel, also removed one coil from the firing pin spring to make up for the material a removed at the front of the pin (ie reduced AOL). With a newly designed full length firing pin the spring would not be shortened, this was done for research purposes.

Attachment E:  This is a picture of the resulting firing pin impression, each round fired on the first attempt. I have repeated the successful 10 round cycle with 100% ignition on each attempt. (Even with main spring adjustment screwed backed out 1/2 turn for testing purposes. (Eley and Federal bulk ammo)  Again, 100% ignition.  You will notice that my firing pins strikes do not hit the outer rim and impressions are wider like you would see with a rifle firing pin impression.

* Another benefit of the modified firing pin:  Because the 617 revolver firing pin strikes on the outside edge of the 22 rim fire cartridge it also will hit the cylinder when dry firing with an empty cylinder, causing dings in the cylinder.  A properly modified firing pin nose could eliminate these dry fire dings.  The firing pin retainer pin will ensure proper firing pin north-south alignment.

Food for thought: A permanent Model 617 FTF fix would be to reposition the firing pin path by modifying the Model 617 revolver. Another fix would be to manufacture the Model 617 specific firing pin with modifications previously noted. Of course the modified pin would be specific to the Model 617 and not intended for center fire revolvers.

NOTE: This modification only works with an unmodified factory hammer or the Apex Mass Driver Hammer, hammer weight is essential.

In closing it works!

sammons:
Nice fix. Seems S&W has a problem they should be responsible for. Sure looks like you got it zero'd in on the sweet spot.

Had similar FTF situation on two of my well used riffles, they were getting like strikes and more outside of rim. My little Ithica was actualy leaving a burr on the outside. Other was my old Marlin 39a which was just leaving the light strike. I pulled the firing pin on both, decided they were slightly mushroomed on strike end. Hammered them out and dressed the end back up with a file. They are both back to 100% fire now.

sixball:
Nice work. I'm surprised S&W isn't fixing this. That is a great revolver I wish I had one. It is cool ti be able to fix your own stuff.

I've been putting some of my tools back in service. I put a 3 axis DRO on my little mill and fixed a broken table on the big belt/disc sander. Now I'm in the middle of replacing some broken gears on my lathe. I have to make one of them. They were broken when I got it but I just didn't use the power feed. I'm also doing a major cleaning while it is apart and replacing some bearings. It is all part of the shop cleanup. Parts in place take up less space than parts piled around in the way. It will be so nice to have it all working so I can get on with the roadster again. I also found the roughing reamer I needed for 219 Donaldson Wasp. Now I have to find a new barrel with the right twist, I haven't decided what yet. I like it and making rounds for it satisfies some of my mechanical needs. I i's pretty bad ass for a little guy.

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