Dry firing

[Dead Eye Dave]

What does dry firing do to a pistol that doesn't happen when live firing?  I don't dry fire as I listen to the experts on it, but I am curios as to what it does that is bad.  I just want to know for my own info.

Thanks

DB

[Driftwood Johnson]

Howdy

To a large extent it depends on the shape of the firing pin, and how it is mounted to the gun. As they say about jumping off tall buildings, it isn't the fall, it's the short stop at the end that hurts. When you pull the trigger on any gun, particularly if it has a hammer mounted firing pin, even though to our eye the motion is instantaneous, the motion actually starts rather slowly, as the spring starts releasing its energy. But the the forward motion stops in an instant when the hammer slams into the frame of the gun. This rapid slowing down is called decelleration and it is almost instantantaneous in this case. When the hammer bottoms out on the frame, the firing pin is unsupported. It is passing through the hole in the frame, and when the hammer slams to a stop, the firing pin wants to keep right on going. In the worst case scenario, the narrow tip of the firing pin will shear off and keep right on going. When firing the gun normally, the firing pin strikes the primer a short distance before the hammer slams against the frame. As the firing pin dents the primer it actually brings the firing pin to a gradual stop and cushions it, supporting the tip of the pin when the hammer slams to a stop. This way, the tip of the pin slows down enough that it is not over stressed, and everything is fine.

Generally speaking, the narrower and longer the the tip of the firing pin, the more susceptable it is too this type of damage. Ruger firing pins are short and squat. They almost never break. It is more common for a transfer bar to break on a Ruger than a firing pin. Simillarly, rifle firing pins are long and thin. The body seldom breaks, but it is possible for the very tip to separate if there is nothing to cushion it.

The perfect way to cushion a firing pin is with a live primer. Snap caps are also very good, either the spring loaded ones or the ones with a hard rubbery material in place of a primer. Spent primers ARE NOT good at cushioning firing pins. After a few strikes they take on the shape of the firing pin itself and are no longer cushioning the pin from that sudden stop. By the time the firing pin stops, the hammer has already slammed to a stop and the primer is not cushioning anything. Some folks like to make their own snap caps from spent cases with some silicone caulking in the primer pocket. Personally I think this is too soft and does not offer enough protection to the firing pin. I prefer the rubber from a pencil erasor, it is a little bit harder.

All this is not to say that you are going to break a firing pin the first time you drop the hammer on an empty chamber. But do it enough, and you may break a firing pin.

[Old Top]

Dead Eye,

Driftwood has covered this much better then I ever could, but one thing he did not mention that I have found is that dry fireing may cause the frame to bulge around the fireing pin hole which if you have tight tolerances or a high primer will cause it to drag on the bulge.

Old Top

[Driftwood Johnson]

Howdy Again

Ya know, Old Top, I have heard that before, but it really doesn't make any sense to me. I have had 2 Cimarron Cattlemen, and both of them have had the tendency to form a burr as you are referring to where the firing pin emerges from the hole in the frame. What happens is as the firing pin 'finds' its way through the hole in the frame, it can peen over the steel of the frame and raise a burr on the inside of the frame. The steel of the frame is relatively soft, and easily deforms. Both of my Cattlemen had this tendency to raise a burr, and it was so bad in one that I had trouble unloading the gun of live ammunition one day. The cylinder locked up tight because of the primer stuck on the raised burr, and I could not rotate the cylinder to unload the gun. I had a devil of a time unloading the gun, but finally got it unloaded. But I very seldom dry fire guns, yet both of these Cimarrons exhibited this tendency to raise a burr around the firing pin hole, just from normal firing. I really doubt if it is dry firing per se that causes this problem, I suspect any firing, dry or live, tends to cause it. When you stop and think about it, there is no difference in the way the firing pin emerges from the frame, whether there is a live round present or not.

Anyway, I eventually got rid of the one Cattleman, it had multiple problems. I still have the other one, and everyonce in a while I have to stone the recoil shield to keep that burr down.

Of course, that's why Colt presses a hardened steel insert into the frame around the firing pin hole, to prevent such a burr from being raised.

[Old Top]

Driftwood,

I agree that once again you have explained the problem better then I have, however I had two pistols of the same manufacture and caliber, one I practiced with by dry fireing (admitedly with out snap caps) and the other I did not dry fire.  The one that was dryfired put a burr as you described and the one not dryfired did not, that is what I based my observation on.  But admitedly my experience is limited.

Old Top

[Driftwood Johnson]

Old Top

I have certainly heard the theory before about dry firing raising a burr. And from some very respected gunsmiths too.

Are you sure that the burr did not get raised on your pistol simply because it was the one practiced with while dry firing, and you simply dropped the hammer a lot more on that one?

It also probably has to do with the way the firing pin rides through the frame, and it is entirely conceiveable that there are subtle differences from gun to gun. One may tend to raier burrs easily, one may not.

Anyhoo, nice talking to ya.

[Old Top]

Driftwood,

You could be right but I have not dryfired (with out snapcaps) and the problem has not returned.  So who knows but your explanation is probably correct.

Old Top