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Firing pins.

Discussion in 'Handguns: General Discussion' started by jimbo555, Jan 30, 2012.

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  1. jimbo555

    jimbo555 Member

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    Is a hammer mounted firing pin typically found on older colt and s&w revolvers the most reliable type for positive primer ignition? It seems there are a lot of complaints on todays new firearms of light primer strikes.
     
  2. Tcruse

    Tcruse Member

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    There are a couple of things happening to cause the "primer issues".

    1) People are shooting more "Lower Priced" (many times like Tula) ammunication that uses primers that require a better hit.

    2) Many times people are attempting to lighted trigger pull (usually on striker fired) and that many times involved using a lighter striker spring, reduceing the stike on the primer

    3) "Lower Priced" ammo also usually results in "Dirty" ammo that causes striker channels to be filled with residue that also slows firing ping performance.

    For example, a relatively clean stock Glock can shoot the Russian steel ammo all day and never see a mis-fire.
     
  3. Standing Wolf

    Standing Wolf Member in memoriam

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    Hammer-mounted firing pins were the original idea. Frame-mounted firing pins have come to prevail because they're mechanically simpler and do a better job of keeping the pins out of harm's way. A hammer-mounted pin moves in an arc; a frame-mounted pin moves back and forth in a smaller channel that's less likely to accumulate grit, grime, gunk, and the like. A hammer-mounted pin is easier to bend or break off by accident, though some frame-mounted pins aren't user-serviceable.
     
  4. Japle

    Japle Member

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    If you have a S&W revolver with a frame-mounted firing pin, you can buy an extended firing pin and increase reliability. I've done this on my guns and it makes a world of difference.

    Too bad, I have an older M-29 with a hammer-mounted FP and no one makes a longer replacement.
     
  5. MrBorland

    MrBorland Moderator

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    One can also try a reduced-power firing pin spring. If the action's been lightened, a stock FP spring can rob the hammer strike of just enough oompf to cause light strikes.


    Check out Toolguy's suggestion here (post #4):

    http://www.brianenos.com/forums/index.php?showtopic=144426
     
  6. Mizar

    Mizar Member

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    If you "need" a longer than standard hammer mounted firing pin on your revolver something is out of spec (headspace). Those pins are not of inertial type.

    Boris
     
  7. Driftwood Johnson

    Driftwood Johnson Member

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    Most of the complaints I hear about light primer strikes are because guys are using main springs that are too light.

    Any firearm has a certain amount of internal friction. Most firearms made today are mass produced and the parts are not hand fitted, so there is more internal friction left in the lockwork. Friction in the form of resistance to the hammer rotating, and excess friction with a separate firing pin riding in a slot or cut in the frame. So today manufacturers routinely install springs that are strong enough to overcome the internal friction and still impart enough energy to the firing pin for positive ignition.

    Guys think they will get a lighter trigger pull by putting in a lighter hammer spring, which is true. But if you go ahead and install lighter springs without doing something about the excess friction in the system, you are asking for light primer strikes that do not reliably set off primers.

    On top of that, different primers have harder and softer cups. In my experience, Federal primers are the softest and easiest to ignite. So sometimes guys will install lighter springs that will reliably set off Federal primers, but when they can't find Federals, like happened a few years ago, they find out their gun may not reliably fire Winchester or CCI primers.

    Bottom line is, replacing springs is not the same as an action job.
     
  8. Japle

    Japle Member

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    MrBorland,

    Thanks for the link. That's exactly what I needed.
     
  9. Drail

    Drail Member

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    Use Federal whenever possible. If you lighten your springs avoid CCI/Speer like the plague. Actually lightening hammer springs can cause a whole bunch of other problems. Unless you have a physical handicap it's better to build the strength in your gun hand rather than lighten the trigger pull so it seems "easier". Ever seen Jerry Miculek shoot a DA revolver so fast it sounds like a full auto gun? He uses extra power springs in his guns so he gets faster locktime and faster trigger rest. After years of learning to run a revolver using factory strength springs he decided they were slowing him down. I didn't quite believe it when I heard him explain it and after trying it, he is right.
     
    Last edited: Jan 31, 2012
  10. brickeyee

    brickeyee Member

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    Please explain how a stronger spring produces lighter hits.
     
  11. F-111 John

    F-111 John Member

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    A stronger firing pin return spring can cause lighter primer strikes because the hammer has to overcome the resistance of the firing pin return spring in order to move the firing pin forward.
     
  12. Jim K

    Jim K Member

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    A lot of problems with "light strikes" don't come from the type of firing pin, they come from people who don't know what they are doing playing with the gun's innards to lighten this or fix that. One more time, let me try to get a point across.

    EVERY maker of serious firearms builds extra power, in the form of spring tension, into the actions of the guns they make. That extra power is intended to prevent misfires and failures under adverse conditions like cold, dirt, etc. People who tamper with the mechanism to make it easier to work remove that extra edge of power. They then express shock and surprise when the gun fails to ignite hard primers, or won't fire when dirty, etc., etc.

    Another point for those who can understand a little physics. It takes a certain amount of striker momentum to fire a primer. The required momentum can change depending on many factors, like the primer cup material. Momentum is mass times velocity. On an S&W J frame (a favorite of the "action job" and "bobbed hammer" crew), the hammer is very light already because the gun itself is small. If the springs are reduced and/or the hammer mass is reduced, the remaining momentum just might not be enough to fire even a normal primer, let alone a hard one. The result? In the extreme, you die holding a gun with a sweet trigger pull, and you can be very proud of your action job.

    Jim
     
  13. JohnKSa

    JohnKSa Member

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    To add to Jim's comments. DA trigger pulls often result in lighter strikes than SA shots due to reduced hammer travel.

    I think some folks put in lighter springs, check the gun out firing SA at the range but never check carefully enough to verify that the DA pull is also completely reliable.

    I recall reading a self-defense encounter article in which the defender's revolver misfired several times due to lightened springs that the defender had installed. He was firing his revolver DA in the heat of the moment, but dollars to donuts, he tested it SA only after putting in the spring kit--if he tested it at all.

    Part of the "extra" power is there to insure that there's enough oomph to light off a primer with the reduced impact from a DA pull.

    I play around a lot modifying my range toys, but I will not go to lighter springs in self-defense guns. If I can't manage the trigger on a particular gun then it's not a good choice for self-defense for me and I look for something else.
    A firing pin that is too long is almost as bad as one that's too short. Unless there's a known issue with the firearm that makes a longer firing pin appropriate, it's not a good idea to blindly install one. Too much firing pin protrusion can cause serious issues.
     
  14. Mizar

    Mizar Member

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    I'm a little surprised that nobody suggested yet to make his firing pin tip more pointed, to sharpen it - you know, those stock firing pins are so blunt and do not ignite primers well... :neener:

    Boris
     
  15. MrBorland

    MrBorland Moderator

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    Technically, it's not momentum, or even kinetic energy that sets off primers, but power - energy delivered per time. Bobbing the hammer, for instance, allows one to get away with a lighter action before reliability becomes an issue, and the reason is the lighter hammer delivers a more powerful strike.

    If you reduce a hammer's mass, you increase it's speed. Energy remains the same, as it's being supplied by the mainspring, so power goes up because that same energy is being delivered in less time. The effect on the firing pin is akin to a nail being driven - a 1lb carpenter's hammer is a better tool than a 3lb sledge for this because it travels faster and delivers more power.

    As far as momentum, you'd ideally want to reduce it, since it's momentum that jars the muzzle (and sight picture) upon hammer strike, reducing accuracy. Fortunately, reduced hammer mass can trump increased speed, so momentum can go down while increasing power. A win-win.

    If you haven't see it yet, check out my vid below. I'll make 2 points here: First, is that this revolver has a frame-mounted firing pin, uses a radically-bobbed hammer, and has a DA trigger pull of about 7.5 lbs, but shoots everything I put through it, including CCI primers. The other point is that the very light hammer delivers so little momentum, I can keep a nickel balanced on edge during hammer strike (and the gun's an absolute tack driver, btw). I tried the same thing in another vid using my stock M65, but could never get the coin to stay upon hammer strike.

    http://www.youtube.com/watch?v=lmy5mkjpUNI
     
  16. Driftwood Johnson

    Driftwood Johnson Member

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    A primer that is too sharp runs the risk of puncturing the primer. This allows hot gasses to vent back towards the shooter. One particular Uberti design of a conversion revolver has firing pins that are too sharp and they consistently puncture primers. One smith even offers after market firing pins for this model that are blunter to correct this problem.

    But the other part of that equation is that a lighter hammer may not have enough momentum to overcome resistance to pivoting in the form of friction. I put Volquartsen after market parts into one of my Ruger Mark IIs. The new hammer and trigger resulted in a much lighter and crisper trigger pull. But I was getting misfires with them in there. The hammer is skeletonized to reduce its mass. When I put the original hammer back in the misfire problem went away. There really was no way to further reduce the friction the hammer was seeing, so I left the new trigger and the OEM hammer in place. Not quite as nice a trigger pull as with the new hammer, but still better than stock and I don't get misfires. Reducing hammer mass can be a tricky thing, just like reducing spring strength. Go to far and you may upset the delicate balance of things.
     
  17. MrBorland

    MrBorland Moderator

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    How do you know for sure it was a friction issue and not a poorly-matched spring?

    I do agree that hammer mass must be balanced against spring strength, and that reducing hammer mass doesn't give one a free pass on spring strength. It's still possible to spring a gun too lightly even with a lightened hammer.

    It also matters where the mass is removed from the hammer. To be most effective, material needs to be removed such that the hammer's center of gravity is moved closer to the pivot.
     
  18. Mizar

    Mizar Member

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    Driftwood, I was trying to be ironic with my comment.

    MrBorland - our friend Driftwood changed only the hammer and the trigger - he doesn't mention changing the main spring. You stated -
    The hammer in question has a large hole drilled in the top part of it resulting in
    Can you please explain this mismatch between theory and practice?

    Boris
     
  19. MrBorland

    MrBorland Moderator

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    Reducing hammer mass and/or brings the center of gravity closer to the pivot and lowers the hammer's Moment of Inertia, which is the hammer's resistance to any change in velocity.

    A lighter hammer accelerates faster because it has less resistance to the spring force. It's lower MoI also makes it capable of quicker deceleration (more power delivered to the FP), but also more sensitive to an opposing force such as friction during it's travel, which can rob power from the hammer strike.
     
  20. Mizar

    Mizar Member

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    A lighter hammer accelerates faster to a certain degree - every spring has it's limits for speed of decompressing - i.e. it can't accelerate it's speed infinitely. Quicker deceleration of the hammer has nothing to do with the "power" applied to the firing pin - you need force, momentum because inertial FP's also obey Sir Newton's First Law. Light hammers are known to cause misfires (stock mainspring left in place). Lets assume (just for the argument) that good gun manufacturers do know how to produce weapons. Weapons that work... And, just maybe, they already engineered that heavy hammer to work right with a ridiculously heavy mainspring. Or that short, blunt firing pin... In ideal and simplified situations light hammers DO work, but in practice cows are not spherical and do not live in vacuum.

    Boris
     
  21. MrBorland

    MrBorland Moderator

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    Boris -

    Some of your points are well-taken: If spring limits cause hammer speed to plateau at some point as hammer mass is decreased, an overly light hammer would lose power, and cause light strikes. Light hammers can cause misfires, then.

    It likely has much to do with the spring/hammer design of the particular gun, and that lower cutoff would need to be determined empirically. Nonetheless, within limits, even the real-world miasma we live in, it's my experience that a lightened hammer can result in a lighter action with acceptable reliability. YMMV, of course.
     
  22. BCRider

    BCRider Member

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    It's been my experience that when it comes to reliability at firing the primers that the hammer or firing pin SPEED is the key factor. This actually fits in with MrBorland's posts.

    Look at any number of the skeltonized hammer's on various semi auto handguns. Some of them are far lighter and have lower moments for inertia than even a bobbed S&W hammer. Yet they hit the firing pins with enough impact energy smartly enough to set off the primers reliably.

    An example is one of my CZ's which has a 13 lb mainspring that I use in matches. It has an almost silly light effort needed to thumb cock the hammer. And the tiny little lightweight competition hammer. Yet I can't remember it ever having any light strikes. But the light spring is more than enough to accelerate the light hammer to what apparently meets the speed and impact power needed for the relatively heavy firing pin in that gun to set off the primers.

    If it were about mass and power then this gun would not fire. But if I'm right about speed of the pin striking the primer being the primary requirement then it all makes sense.

    If it were only pressure then we'd see more of the primers crushed by reloading presses being set off. But I've only heard about two cases of primers in a press that didn't load correctly being crushed and igniting. But I'mve personally deformed and maimed at least a dozen primers into shapeless lumps with my own press. And all without any POP to liven up my day.
     
  23. Mizar

    Mizar Member

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    BCRider, the idea is that gun manufacturers already did a setup that works reliably. In your case with the competition CZ - it's a factory setup FOR competition. Let me give you an example - Browning HP MkIII - one very popular modification is to replace the mainspring with lighter one to get a better trigger pull. The argument is that older Hi-Powers had a lighter mainspring and that is a fact. But with that setup we have several points that most of the "customisers" miss:
    1. The firing pin spring on MkIII is heavier than the old models - if you leave the stock spring in place you will get lighter primer hits.
    2. Mainsprings do slow the slide on recoil.
    3. On the original P35's the firing spring plate has a smaller radius than today's commercial Hi-Powers (just like 1911 vs 1911A1 FSP)- FSP with smaller radius do slow more the slide on recoil.
    I'm not saying that you are wrong just that it is not that simple and straight forward like some people think.

    Boris
     
  24. Slamfire

    Slamfire Member

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    I believe so.

    I call the hammer mounted firing pin mechanism a direct strike mechanism. All the KE or Momentum (whatever makes you happy) goes directly into the primer. Mechanisms that transfer energy through a transfer bar, then a free floating firing pin, lose energy through each transfer. Every energy translation generates entropy and that robs energy from the final firing pin strike.

    I believe this is why my late model S&W's have stronger mainsprings. The mainspring has to start out stronger to deliver the same strike energy as a direct strike mechanism. Since I have to over come that mainspring resistance to double action my revolvers, I prefer a mechanism with a lighter double action pull.

    Transfer bars break. Transfer bars are complicated pieces of small metal. I have had transfer bars break in FIE Hombre’s and this Ruger Super Blackhawk. Once the transfer bar breaks, you cannot fire the mechanism. Might as well use the pistol as a hammer until you get a new transfer bar.

    Direct strike mechanisms don’t have a transfer bar in the way and just by the elimination of a part, the mechanism will be more reliable as you have eliminated a failure mechanism.

    I have had primer cupping around my direct strike S&W’s and in mechanisms with those frame mounted free floating firing pins. On the direct strike mechanisms I can manually pull the hammer and firing pin back and clear the jam. You cannot do this with those mechanisms with frame mounted firing pins as the firing pin is not mechanically retracted. A number of times I have had a similiar frustrating experience as this gentleman did with his transfer bar mechanism.

    http://www.zombiehunters.org/forum/viewtopic.php?f=31&t=34819&start=168


    [​IMG]

    [​IMG]

    [​IMG]

    I called S&W to ask why they had stopped using the hammer mounted firing pin. It all came down to costs. It took a dedicated machine and person to drill the frame holes. They could not figure out a way to automate the drilling process on their CNC machines.
     
    Last edited: Feb 5, 2012
  25. MrBorland

    MrBorland Moderator

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    Smiths use a hammer block, not a transfer bar. The hammer contacts the firing pin directly, and the hammer block can be removed entirely.

    Also, a S&W hammer-mounted firing pin also loses energy as it pivots against a spring when contacting the firing pin, and it's not clear to me that less energy is lost with this arrangement.

    Nor is it clear to me that newer Smiths have stronger mainsprings, either. Is there some data or something from S&W to verify this? I'm not trying to argue they don't - just trying to learn.


    True, but that setup is rarely immutable, or the only setup that will work. A whole sub-industry of gunsmithing, aftermarket parts & customization attests to that.

    A company's final design spec are the result of many elements beyond the basic engineering (e.g. manufacturing costs, marketability, liability) - that may or may not be important to any particular individual.
     
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