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Thread: Recoil Spring Function

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  1. #1
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    Recoil Spring Function

    Springs! Specifically...recoil springs. The subject of much debate and conjecture...and one of the least-understood facets of the gun.
    I've never really understood how they came to be known as "recoil"
    springs in handguns...and "action" springs in rifles and shotguns...but that's academic at this point...so we'll just call'em recoil springs....but technically speaking, they're action springs. The recoil function is simply
    a means to transfer kinetic energy to the spring, so that the other half of the cycle...feeding and returning to battery... can be completed.

    It's an auto-LOADER...not an auto extractor/ejector. The primary function
    of the spring is to reload the chamber without manual assistance. All else is secondary...

    The spring can also be a means to absorb recoil and spread its effects out over a longer time frame...as with the Howitzer...but weapons like these are single-shot, and the heavy recoil is controlled by these springs in order to negate having to reposition the weapon for follow-up shots.
    In systems such as these...the recoil spring is truly a recoil spring.

    A few things to keep in mind:

    Springs work both ways. They compress to store energy, and they
    un-compress to release energy.

    They have to balance their function so that they'll be able to perform both tasks within the design parameters of the machine that they're assigned to. The engineers who settled on a particular spring rate had very good reasons for their choice. Changing that balance by going very far out of the window very often has adverse effects on the function of the machine that may not always be immediately apparent.

    The speed of the complete cycle of an autopistol doesn't change to any real degree by changing the rate of the recoil spring. The total time difference will be within small fractions of a second, if at all. The change in speed is in one direction, and is compensated for in the reverse direction. The heavier spring slows the slide in recoil, but speeds it up on the return to battery, and vice versa.

    Energy can't be destroyed. It can only be redirected.
    ******************************

    The recoil spring in a locked-breech weapon doesn't prevent impact damage to the frame and slide unless the spring is so heavy that it doesn't allow full travel. It only softens the blow...a little. While it's true that a heavier spring softens the blow a little more, it does so at the expense of the parts that impact on the return to battery. In the 1911, this would be the lower barrel lug...specifically the feet...and the slidestop crosspin. So...you 18 and 20 pound spring users are offering the frame and slide abutments a bit more protection while redirecting the impact forces into another area of the gun. Think about it. The frame and slide impact surfaces are engineered to absorb shock stresses. The lower lug feet aren't.

    The recoil spring in a locked-breech design doesn't do anything at all to contain chamber pressures, and it has very little to do with the timing of the unlocking phase.
    ************************

    In the recoil function study, we've established that the beginning of the unlocking event comes after the bullet is gone, and chamber pressures have fallen to nearly nothing. It has to. If unlocking began while the bullet was still in the barrel, a case rupture would almost surely be certain with every round fired. A couple years ago, master pistolsmith and mad scientist Ned Christiansen fired a 1911 pistol repeatedly without a recoil spring...without ill effect, and with very little change in point of impact on target as fired from a machine rest...offering proof that the unlock timing
    was only affected by the spring's preload and compression during the
    first 1/10th inch of slide travel. The preload of a 16-pound spring in a 5-inch gun averages about 3 pounds. An extra 1/10th inch of compression would increase that preload very little. So, the difference in the effect on unlock timing between a 16 pound spring and a 20-pound spring would be about the same as the pressure that you put on the space bar on your keyboard as you respond to this.

    A heavier-than-standard recoil spring DOES have an effect on the
    timing of the return to battery. While the dynamics of the event will be mechanically the same...it all happens at a faster rate. Think of the spark advance in an automobile's ignition system. As engine rpms increase, the spark must occur at an earlier point in the piston's position before TDC in order to keep up, or the engine suffers a loss of overall performance.

    In the case of the autopistol, the problem is with the magazine's ability to keep up with the slide. The magazine spring has a daunting task. It not only has to lift the rounds upward in the magazine while being jerked around during the pistol's recoil cycle...it has to get the next round into position in time to meet the breechface. The faster the slide moves as it returns to battery, the less time the magazine has to put the next round into position. If the magazine spring isn't up to the task, we have classic bolt-over-base and rideover feed malfunctions. In these...the slide is outrunning the magazine.

    The second part of the problem is that...if a jam does occur...the heavily sprung slide jams it harder. Think of a wedge-type doorstop. If you push it in place with thumb pressure, you can pull it out easily. If you kick it in place hard with your foot...it's tougher to remove. Often...when we have
    failures to return to battery with the round part-way into the chamber...we get the advice to "Try a stronger spring." While a stronger spring may well
    force the round to chamber in spite of the problem...this is usually counterproductive. Better to address the real problem than put a band-aid on it. If the gun is correctly set up, it should feed and go into battery easily with an 8 or 10 pound spring.
    Likes (1) :
    MuyModesto (25th July 2020)

    Last edited by 1911Tuner; 21st December 2004 at 11:45.


  2. #2
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    Quite informative

    Hello Tuner,
    You've done it again. Great explanation, informative and understandable. Thanks for the effort you're putting out for the inquiring 1911 community.
    If you could, you've mentioned preload spring rating and the change of pressure it takes to compress the spring. Could you elaborate alittle more, either here or in another thread. I'm interested to know that general info ie: at what percent of compression does it reach 25%, 50%, 100% or more of the RATED poundage. Also is the curve basically the same during expansion. Is this information a basic spring thing in different amounts.
    Can you explain the difference between the above and a variable rate spring? Thanx again....

  3. #3
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    Angry Mo' Spring Things

    Whew! That's a tall order for one reply, mah fren...but I'll give it a shot.

    The Ordnance-Spec recoil spring calls for 30 coils of .043 diameter with a total free length of 6.55 inches. This spring is to provide a total fully compressed tension of 17.36 pounds, and compression strength at 73%
    compressed length of 13.55 pounds...which would be close to the average compressed length/strength as installed in a gun at full slide travel...or maybe a little more. Tension increase is progressive...or it gets higher the more the spring is compressed...but these figures work out to average 2.65 pounds per inch of compression.

    People sometimes confuse spring loading with spring rate. The charactistics of the above spring can be completely changed by winding it with a different spacing between coils...or a different wire diameter. Wider spacing increase
    the total loading and the rate of loading per inch of compression...and the rate is the main determining factor in how the spring behaves as it unloads
    it stored energy. That same spring with wider spacing...and hence a greater free length...will move the slide into battery faster than with the above specifications. It will also slow the slide in recoil at a faster rate, as well as providing a greater total resistance at a given compressed length.

    Thus...a smaller diameter wire could provide the same total compressed
    tension of a 16 pound spring, with the unloading speed of a heavier spring.
    Springs are simple machines that become more complicated as you dig deeper.
    One tiny, almost insignifigant change in the design produces a much different behavior.

    As near as I can tell, packaged aftermarket springs' rated load are measured
    at average installed compression length at full travel rather than at full compression. So...a Wolff spring rated at 16 pounds would be a bit stouter
    than design specs. Of course, this assumes that the spring produces its advertised loading...which isn't always the case. The vary quite a bit sometimes. Then, there's the tolerances within the gun itself that can vary
    the amount of compression length of the spring. This variation would be minimal...but everything means SOMEthing.

    I've been researching factory recoil springs for a little over 25 years. Whenever one of my dealer pals gets in a new Colt or Springfield pistol, I go and test the recoil springs. I have yet to run into a factory installed recoil spring that meets the accepted "standard" of 16 pounds in a 5-inch Colt...or 18 in a Colt Commander. They run about a pound and a half lighter on average across the board. Early Springfields 5-inch guns did, but they seem to have altered their stance on spring rates in the last 5 years or so. They're lighter.

    Variable springs are simply springs that are wound progressively, with the coils
    being closer together for the initial slide movement, and becoming farther apart toward the back. Simply put...the compression rate steps up faster
    as the spring compresses. The theory is...I suppose...to provide slower slide speeds on the return to battery without sacrificing frame to slide buffering.
    Thus...in theory...an 18 pound variable spring would behave like an 18-pound spring near the end of recoil, when the slide smacks the frame...and still behave more like a 15 or 16 pound spring as it unloads and returns to battery.
    I've never played with variable springs, so I can't offer any pros or cons.

    In practice, they would seem to work much like a dual spring, where the inner spring is shorter and doesn't really come into play until the outer spring compresses far enough to let the inner spring's effect begin. A perfect example is the Springco device, where the guide rod flange is spring loaded,
    and provides a buffering effect as it slows the slide abruptly just befor impact.
    On the return to battery, its effect would stop as soon as the slide moved
    far enough to get away from it. While the slide would be boosted forward
    for a short distance, this would..in a way...mimic the rebound effect of the
    slide hitting the steel guide rod flange and bouncing off. Not exactly...but
    probably a close approximation. A recoil buffer without the drawbacks of
    a soft impact surface.

    I've always subscribed to the use of a small radius firing pin stop, a full-power mainspring, and a standard recoil spring...or even lighter...to keep the slide's recoil velocity and impact down. The FP stop also has the added advantage of delaying the slide for a fraction of a second...and the beginning of the barrel unlock sequence...and gives the chamber pressure a tick longer to drop.
    The small radius on the stop isn't the result of a breakthrough discovery that just came in recent times. It was in the original design, changed at the request of the Ordnance Department to make the guns easier to hand-cycle with the hammer down. I would be willing to bet that the recoil spring's load rating was also increased slightly to compensate.

  4. #4
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    Sorry

    I apologize. I did not realize the scope of the issue or of your response. I'm going to have to read this one a couple of times. THANKS

  5. #5
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    Apologize?

    One thing I've learned is...How ya gonna understand somethin' if ya don't ask questions?

  6. #6
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    Thumbs up ****

    Quote Originally Posted by 1911Tuner
    One thing I've learned is...How ya gonna understand somethin' if ya don't ask questions?
    Tuner you amaze me, I nevwer knew you got that deep into the mechanics of the 1911. Sure am glad that my past work experiences have been in the mechanic and machining field and I can totally understand what you are saying. The 14# Wolff spring works well in my SA full size with the shock buff, my next project after a few more round is to do the firing pin stop with a smaller radius and see what that does. The gun is running fine at this time. Bear wants to know if that pack of pooches got their treats?
    Bear's Story .

    If you have no money and few possesions, if you have a dog you are still rich.

  7. #7
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    Mechanics

    Howdy Len! Yep...Wasn't too bad for off the top of my head, was it?
    The 1911 is an obsession at times.

    The dogs are munchin' on Beggin' Strips as we speak. They said:

    Woof! Woofwoof...woof. Woff woof woof woof ...woof WOOF!

    That's Colliespeak for : "Three cheers for the Bear!"

  8. #8
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    Question recoil springs

    Quote Originally Posted by 1911Tuner
    Howdy Len! Yep...Wasn't too bad for off the top of my head, was it?
    The 1911 is an obsession at times.

    The dogs are munchin' on Beggin' Strips as we speak. They said:

    Woof! Woofwoof...woof. Woff woof woof woof ...woof WOOF!

    That's Colliespeak for : "Three cheers for the Bear!"


    And a Woooooooooooooooooooofie from Bear to you and the pack. You al,ost sound like you know what you are talking about, jist putting you on buddy. That was well put and now I understand more of the working, but to a lot of people without the right background will be totally confused. Tough luck, have somone who knows what they are doing fix it, rather than screw it up yourself. Got and adjustable rear sight coming for the big gun, ordered it from SA on their loaded certificate for 29 bucks, normally 49, made for them by PSI and they retail it for 69.95. Which way do they drive out, I believe from left to right?
    Bear's Story .

    If you have no money and few possesions, if you have a dog you are still rich.

  9. #9
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    I think I just experienced what you're talking about last week during my league shoot. I had just replaced the recoil spring in my Wilson KZ with their recommended 18.5 spring. Within the first 40 rounds I had a failure to eject completely 4 times. The empty would get caught in the ejection port. After that function was fine - so I assume the spring actually weakened a little in those first 40 rounds. Think I'll try the 16 pound next time.

  10. #10
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    re: Spring

    Howdy Wilson, and welcome aboard.

    You had a first-hand experience with what's known as "Spring Set." All new springs that have been stored at free length are a bit stronger than their
    numbers indicate until they take a set. Next time you change out a spring,
    you can avoid problems during the settling-in period by Locking the slide back and leaving it for a few hours...Overnight will probably do. This also very often occurs with new mainsprings unless you use one that's under spec
    rating.

    Just for what it's worth...If your pistol showed problems during the spring's break-in period, it's a pretty good sign that you need a bit lighter spring
    for that gun firing that particular ammunition.

    Luck!

    Tuner

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