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As I said, this gun is only a few months old -- there is nothing wrong with the hammer spring. And I bought and installed a replacement FP made by Browning and one made by J&P Custom, and they made no difference whatsoever.

Here's all I know: either factory FP, lower or upper, when pushed all the way forward with the breach-face exposed goes in past "flush" with the back of the action. So you lose a few thou there.

I almost never see ammo with flush primer caps -- they are almost always seated deeper. So you lose a few thou there.

Combine the two and that puts your theory in serious doubt. And if having a shell in the chamber would make the upper FP work in a "bridge" shot, why didn't it work in my scenario (rapid second shot)?

Who knows? It could be that I just got an upper FP channel that was drilled a little too shallow. I'm just glad I was (apparently) able to fix it without having to send the gun off for months to be fixed.
My guess is that the original problem was due to several things:

1. Relatively small girl providing little resistance against the recoil of the gun.

2. Soft Touch recoil reducer further reducing the resistance to recoil needed for the gun to operate properly.

3. A factory firing pin that wasn't long enough in protrusion to overcome the problems created by number 1 and 2 above.

4. Ammo that isn't consistent in the seating depth of the primer.

Glad that your longer firing pin is working well to solve the problem for her.
 
Discussion starter · #22 · (Edited)
You need resistance to make a semi-auto cycle, but that has nothing to do with an O/U, except when it comes to the inertia block, which in this case never failed to switch to the upper hammer.

To make sure the gun was going to work for her after I put the modified upper FP in I held the gun loosely in my hands by my waist and fired two shots as fast as I could pull the trigger twice. I don't know how to create less resistance than that.

The upper FP simply needed a spring, like the lower one has. Some Browning engineer got a bright idea for a way to save 25 cents, not realizing that some people fire the second barrel extremely quickly.
 
You need resistance to make a semi-auto cycle, but that has nothing to do with an O/U, except when it comes to the inertia block, which in this case never failed to switch to the upper hammer.

To make sure the gun was going to work for her after I put the modified upper FP in I held the gun loosely in my hands by my waist and fired two shots as fast as I could pull the trigger twice. I don't know how to create less resistance than that.

The upper FP simply needed a spring, like the lower one has. Some Browning engineer got a bright idea for a way to save 25 cents, not realizing that some people fire the second barrel extremely quickly.
I guess that we'll just have to agree to disagree on what the actual cause of the problem was. You think it was because of the top firing pin lacking a return spring. I think that the spring had nothing beneficial to do with it. If anything, the spring would provide for a lesser/softer strike by the firing pin, not a harder one.

This situation is very similar to a modern revolver which has a floating firing pin in the frame along with a hammer block safety that is retracted when the trigger is pulled rearward. It makes no difference if you fire the revolver pointed straight ahead, downward, or any other position. As long as the firing pin doesn't interfere with the rotation of the cylinder, it makes no difference if it is touching the primer or not. It will still ignite the primer if hit with sufficient force by the hammer. And some revolvers have a firing pin that is fixed on the hammer and they work well too if the primer is struck with sufficient force.

It's the same with your O/U. If the firing pin has sufficient length and penetration beyond the breech face and the hammer has sufficient energy in its striking force, then it makes no difference if the firing pin is a few thousands of an inch from the primer or resting on the primer when the hammer falls. It will still ignite/fire if everything else is up to standards.

I'm not convinced, and probably never will be, that reducing the energy (striking force) of the firing pin by introducing a spring is the fix for the problem. The fix was in one or more of the other changes you did when you changed firing pins. It's also possible, although probably not provable, that the girl has changed her speed/timing in the manipulation of the trigger which results in greater functional reliability. As you said, even with the original setup, the problem didn't occur every time. It's likely that she has learned subconsciously how to time the second trigger pull such that it won't malfunction.
 
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Discussion starter · #24 · (Edited)
I took another Citori 20-ga out of my safe and gently lowered the hammer onto the upper FP. When the FP is flush against the hammer (as in the photo) it does not protrude enough to produce reliable primer ignition. You cannot really tell that from the photo but if you feel it you know.

Pulling the hammer back and pushing the upper fP in as far as it will go gets it a few thou farther, but still not the amount of protrusion I like to see.

But as I posted much earlier in this thread, when a shell is in the barrel the primer stops the FP from falling as far forward. So I grabbed a random shell out of my bag, cut it apart (to remove shot, wad and powder), put it in the upper barrel and pulled the trigger, and you can see the indention below.

It was enough to ignite the primer, but the dent is not as deep as I like to see on shotshells. Find a shell with the primer seated just a little deeper and you would have a FTF.

Anyway, now that her gun is fixed Annie is firing that second barrel faster than ever. Her dad is happy because he doesn't have to buy her a Perazzi for a couple more years. :)





 
The dent in a fired primer in a shell with no powder is always more shallow appearing than one that generated the pressure of ignition of the powder which pushed the primer back onto the FP making the dent deeper.
 
Discussion starter · #27 ·
The dent in a fired primer in a shell with no powder is always more shallow appearing than one that generated the pressure of ignition of the powder which pushed the primer back onto the FP making the dent deeper.
I wd assume that. The key facts to me are:

1. If she fired her second barrel slowly (as with sporting pairs) she never got a FTF. Her dad shot that gun a lot before we made it hers, and he never had a FTF with it either.

2. shooting her preferred very fast second barrel with either the factory FP or a new replacement she was getting light strikes often, like, 1/4 - 1/3 of the time. Lengthening the striker portion of the pin (allowing better protrusion) did not change that.

After changing to an FP with a spring she has shot her second barrel rapidly after the first well over 100 times now and has not had a FTF yet.

I can only guess at what the cause(s) are, I just want the problem fixed, and the spring seems to have done it. We will see!
 
I found this thread as I was wondering a similar thing when recently had to replace a broken firing pin in my Rizzini. Bottom pin sprung, upper not. First, that girl shoots fast. Second, I understand the physics of it. What’s happening unintentionally is what works intentionally in an inertia driven semi auto. The pin return spring makes sure the pin doesn’t protrude from the breach face when at rest. If you take the stock off with snap caps in the barrels and press in the firing pins to contact they will set slightly below flush. The rest of the firing process is accomplished by stored inertia in the pin from the hammer strike. That is why the strength of the hammer spring and pin weight change lock speed. When the gun recoils the upper pin, free to move does not move back at the same moment, like the inertia mechanism in a semi, and therefore the striking surface of the pin is not yet fully exposed when she fires the second barrel. A semi would not yet allow a second trigger pull at the point but an o/u is not interlinked the same way. The firing pin spring, small at that, simply works to resist a bit of recoil and get the pin back in the optimum strike position. For 25 cents the simplest answer is probably the correct one. Good luck.
 
It seems that this question of whether the position of the upper firing pin makes any difference in the reliability of ignition can be answered rather easily with a simple experiment.

First, get your gun and a good supply (say a couple of boxes) of ammo and go to the range or a safe place to shoot. Secondly, be sure that the upper firing pin is not gummed up with carbon or anything and that it will move freely when the muzzle is raised and/or lowered.

Now, all you have to do is load the upper barrel, point the gun straight up into the air and fire the round in the upper barrel. Shoot a box of shells this way and record the number of misfires.

Next, you're going to do the same thing except you are going to point the gun straight DOWN. You may need to go up into a tower or on a cliff of some kind so that you don't shoot so close to your toes.

Now, you load the top barrel, point the muzzle straight down and pull the trigger. Shoot the entire box in this same manner. Record the number of misfires.

After shooting a box of shells each way, you simply compare the number of misfires with the muzzle pointed up versus with the muzzle pointed down. If the test was done correctly, the only variable is the position of the upper firing pin at the moment it was hit by the hammer. In one case, the firing pin would be fully rearward when the hammer makes contact with the firing pin. In the other case, the firing pin would be fully forward (resting on the primer) when the hammer makes contact with the firing pin.

Do the above test and get back to us with your results. I don't think there will be any difference unless you just happen to encounter a few shells which have excessively deep-seated primers. BTW, it might be a good idea to take a look at the primers beforehand to see if any appear to be seated excessively deep. If you do encounter any like this, don't use them in the test.
 
It seems that this question of whether the position of the upper firing pin makes any difference in the reliability of ignition can be answered rather easily with a simple experiment.

First, get your gun and a good supply (say a couple of boxes) of ammo and go to the range or a safe place to shoot. Secondly, be sure that the upper firing pin is not gummed up with carbon or anything and that it will move freely when the muzzle is raised and/or lowered.

Now, all you have to do is load the upper barrel, point the gun straight up into the air and fire the round in the upper barrel. Shoot a box of shells this way and record the number of misfires.

Next, you're going to do the same thing except you are going to point the gun straight DOWN. You may need to go up into a tower or on a cliff of some kind so that you don't shoot so close to your toes.

Now, you load the top barrel, point the muzzle straight down and pull the trigger. Shoot the entire box in this same manner. Record the number of misfires.

After shooting a box of shells each way, you simply compare the number of misfires with the muzzle pointed up versus with the muzzle pointed down. If the test was done correctly, the only variable is the position of the upper firing pin at the moment it was hit by the hammer. In one case, the firing pin would be fully rearward when the hammer makes contact with the firing pin. In the other case, the firing pin would be fully forward (resting on the primer) when the hammer makes contact with the firing pin.

Do the above test and get back to us with your results. I don't think there will be any difference unless you just happen to encounter a few shells which have excessively deep-seated primers. BTW, it might be a good idea to take a look at the primers beforehand to see if any appear to be seated excessively deep. If you do encounter any like this, don't use them in the test.
Could this same test be performed be performed with an empty shell and a primer?
 
Could this same test be performed be performed with an empty shell and a primer?
Sure, I don't see why not. Just be sure to use factory loaded shells so that we don't have the issue/question of the quality of the reloads to complicate the picture.
 
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Discussion starter · #32 ·
I'm not convinced, and probably never will be, that reducing the energy (striking force) of the firing pin by introducing a spring is the fix for the problem. The fix was in one or more of the other changes you did when you changed firing pins. It's also possible, although probably not provable, that the girl has changed her speed/timing in the manipulation of the trigger which results in greater functional reliability. As you said, even with the original setup, the problem didn't occur every time. It's likely that she has learned subconsciously how to time the second trigger pull such that it won't malfunction.
A follow up -- here it is over a year later and she has not gotten a single FTF. We went from getting FTF's 25% of the time to getting them 0% of the time. She shoots at least a flat a week and still shoots that second barrel so fast it sounds like a fanfire.

Think whatever you want, but I know that for whatever reason, adding the spring to the upper FP fixed the problem, like flipping a switch.
 
I look forward to seeing your student in the next Olympic finals.

Jim
 
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