GAMO Rifle Question....Are Your Ears Burnin', Hogdogs?
- Thread starter Shane Tuttle
- Start date
Not a metalurgist, but I've owned springers for about the last thirty years.
1) Don't leave them cocked. The spring in an airgun is highly stressed, and most aren't made out of a best-grade wire. James Maccari makes custom springs out of the same stock used to make aircraft valve springs, and he'll also tell you to de-cock.
2) If you want to leave a pellet in them, uncocked, it's very easy. Just "bump" the barrel open to the first stop, where the barrel detent spring/plunger isn't engaged, and stop there. Every break-barrel springer I've used (admittedly, I haven't shot them all) allows this. You now have an uncocked airgun with an exposed breech. Insert a pellet and close the breech. When youre ready to shoot cock the barrel. I've spend hundreds of hours airgun hunting and this is the way I do it.
Lots of things can cause spring breakage- dieseling, too heavy a pellet, etc. Airgun spring are a "consumeable", but with some care can last decades. You can probably find a compatable spring and replace yours with an airgun spring compressor.
If you want an airgun you can leave charged, an older Benjamin or Sheridan is acceptable, but they will most likely have a tiny leak-rate, so if you grab it six months from now it might need a couple of pumps before use.
1) Don't leave them cocked. The spring in an airgun is highly stressed, and most aren't made out of a best-grade wire. James Maccari makes custom springs out of the same stock used to make aircraft valve springs, and he'll also tell you to de-cock.
2) If you want to leave a pellet in them, uncocked, it's very easy. Just "bump" the barrel open to the first stop, where the barrel detent spring/plunger isn't engaged, and stop there. Every break-barrel springer I've used (admittedly, I haven't shot them all) allows this. You now have an uncocked airgun with an exposed breech. Insert a pellet and close the breech. When youre ready to shoot cock the barrel. I've spend hundreds of hours airgun hunting and this is the way I do it.
Lots of things can cause spring breakage- dieseling, too heavy a pellet, etc. Airgun spring are a "consumeable", but with some care can last decades. You can probably find a compatable spring and replace yours with an airgun spring compressor.
If you want an airgun you can leave charged, an older Benjamin or Sheridan is acceptable, but they will most likely have a tiny leak-rate, so if you grab it six months from now it might need a couple of pumps before use.
Evan Thomas
New member
I'm not a metallurgist, and I don't play one on TV... but in the study I cited, a 72-hour uncocked "rest" of the spring wasn't long enough to reverse the effects of long-term compression. It seems entirely possible that, as jammin1237 suggests, a longer rest -- a week? a month? more? -- would completely reverse the negative effects of compression.
The metallurgy question is interesting from an abstract, theoretical viewpoint -- but since compressing the spring over long periods demonstrably reduces the power of the gun, at least in the short run, I don't care all that much about the theory: I can't think of any good reason to leave the thing cocked when it's so easy not to...
"They call it compressing the Spring; it is perfectly easy
No. NO. I'm not gonna go there.
The metallurgy question is interesting from an abstract, theoretical viewpoint -- but since compressing the spring over long periods demonstrably reduces the power of the gun, at least in the short run, I don't care all that much about the theory: I can't think of any good reason to leave the thing cocked when it's so easy not to...
"They call it compressing the Spring; it is perfectly easy
No. NO. I'm not gonna go there.
Spring performance
I think if we look at the task a spring is being used to accomplish, it can give some insight into why some springs seem to weaken while others seem not to weaken.
The spring in a spring piston air rifle is engineered using a design parmeter where any loss of spring pressure will show up as a measureable loss in performance since the entire capacity of the spring is being used to complete the task. Contrast that with a valve spring on a car engine. Anyone who has torn down an engine in a vehicle is advised to do a spring compression measurement to determine whether it is still operating within its design parameters. Many times these older springs can be reused and anyone doing a valve job on the head of an older engine knows that the old springs are weaker than new springs yet they may still contain enough force to efficiently close the valve quickly enough, and with enough force, so as not to be a detriment to engine performance. Same with firearm magazine springs. As long as the spring contains enough force to efficiently advance the next round into position before the bolt returns to pick it up and load it into the chamber, everything is fine. The differences being that the valve spring and the magazine spring are still under load at the extended end of their travel and, if working correctly, will contain a bit more useable force over and above what is needed to perform the task. These springs don't extend themselves completely when released whereas the spring in an airgun is releasing pretty much 100% of the kinetic energy stored when the spring is loaded and any loss in spring force shows up as a measureable loss in velocity.
I think if we look at the task a spring is being used to accomplish, it can give some insight into why some springs seem to weaken while others seem not to weaken.
The spring in a spring piston air rifle is engineered using a design parmeter where any loss of spring pressure will show up as a measureable loss in performance since the entire capacity of the spring is being used to complete the task. Contrast that with a valve spring on a car engine. Anyone who has torn down an engine in a vehicle is advised to do a spring compression measurement to determine whether it is still operating within its design parameters. Many times these older springs can be reused and anyone doing a valve job on the head of an older engine knows that the old springs are weaker than new springs yet they may still contain enough force to efficiently close the valve quickly enough, and with enough force, so as not to be a detriment to engine performance. Same with firearm magazine springs. As long as the spring contains enough force to efficiently advance the next round into position before the bolt returns to pick it up and load it into the chamber, everything is fine. The differences being that the valve spring and the magazine spring are still under load at the extended end of their travel and, if working correctly, will contain a bit more useable force over and above what is needed to perform the task. These springs don't extend themselves completely when released whereas the spring in an airgun is releasing pretty much 100% of the kinetic energy stored when the spring is loaded and any loss in spring force shows up as a measureable loss in velocity.
How about an Aerospace masters student?
Leaving a properly designed spring compressed will not weaken the spring. Period... end of story. That is a proven engineering fact taught at the most fundamental of levels. Properly designed springs will remain in the elastic portion of the stress/strain diagram through its designed stroke. If it is compressed beyond its designed parameters, it will deform plastically which will leave residual stresses in the spring. This does two things: it actually increases spring stiffness, but decreases fatigue life. This is why static springs are usually "preset."
Springs don't get weaker because of leaving them compressed, the get weaker from repeated compressing and then uncompressing (otherwise know as fatigue failure, though with good steel springs, they usually just break before they loose stiffness). I have owned many a bolt action spring rifle, and have never had any loss of power due to leaving it compressed for months at a time. I have a feeling some of these "tests" cited here were either performed poorly, had improperly designed springs, or had outside forces working (such as maybe thermal loads).
HE WINS!
I was hoping someone would come along with some credentials to answer this.
So, assuming a high quality spring is used, no appreciable drop in performance should be detected.
I suspect there might be heat treat issues with some springs used in air guns. A spring not correctly heat treated will not have the same desirable properties as opposed to one correctly heat treated. Like longevity and proper strength for the application the spring was made for.
For example, look at the service life of a well made valve spring. It's service life has many millions (perhaps billions?) of compressions and releases before it ever begins to show signs of needing replacment. In fact, I cannot recall ever having to replace valve springs on any vehicle I've owned. A well made spring lasts for a very long time.
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I emphasized the proper caveat. A lot of people essentially ignore the caveat because: "Who would "improperly design" a spring?" Well, it turns out that sometimes it's a good solution to a design problem.
If a spring is overcompressed then it will weaken from being left compressed. The experiment Vanya quoted is one proof, but it is a repeat of a similar experiment carried out by Tom Gaylord in his R1 book who got exactly the same result. Springs, even the best quality springs, will weaken if they are compressed or stretched too much.
The issue is one of a design tradeoff. Here's what you want from an airgun spring.
Minimum size & weight. Minimum force required to compress. Maximum swept volume and stored energy.
The tradeoff is that the spring is overcompressed when the gun is cocked. It's NOT an issue of quality, even the best springs will weaken from this treatment, but the better the quality the less they tend to weaken.
They could make the springs so that they wouldn't weaken from being left cocked but that would increase the size, weight, or cocking effort or reduce the stored energy by unacceptable amounts. Springs are cheap and easy to replace, but if you make a gun too large and heavy or too hard to cock you can't sell enough of them to make a profit.
In other words, the statement quoted at the top of this post is perfectly correct but ignores the fact that sometimes designers are willing to trade "proper design" for other parameters that they feel are more important.
That's the correct answer. It's just that in some cases "improperly designed springs" turn out to be a good design compromise.
Evan Thomas
New member
JohnKSa said:
Thanks for such a clear explanation, John. And to all who noted facts, evidence, on this topic...
Cool! We're all correct... how often does that happen around here?
jammin1237
New member
once again i have to say that i truly admire all the knowledge and adversity on this forum
back to the original questions.........
will it it hurt to dry fire your gamo? 99.99% probably most likely not...
will the spring lose power if left in a cocked state? do the test and let us all know the "real world" results... if somebody wants to re-engineer/re-manufacture your spring then so be it and more power to them,,, i'll buy one!
cheers
back to the original questions.........
will it it hurt to dry fire your gamo? 99.99% probably most likely not...
will the spring lose power if left in a cocked state? do the test and let us all know the "real world" results... if somebody wants to re-engineer/re-manufacture your spring then so be it and more power to them,,, i'll buy one!
cheers
GAMO, as long as I can remember, has always advertised that dry-firing won't hurt their air-rifles. I know of no other spring-piston airgun manufacturer who makes that claim.
The results of extended cocking time tests with the airguns that I've seen are consistent. Ever airgun/airgun spring combination I've seen tested loses power if it's left cocked a long time. It loses more power the longer it's left cocked and if it's left cocked for very long periods the power loss is significant--25% is not out of the ballpark. The better the quality of the spring, the less the power loss is and the more it tends to "recover" after being left uncompressed for a long rest period. However, none of the springs recovered completely, no matter how long they were allowed to rest uncompressed.
I've never seen a test that included a GAMO airgun so I can't speak definitively about GAMO airguns.
The results of extended cocking time tests with the airguns that I've seen are consistent. Ever airgun/airgun spring combination I've seen tested loses power if it's left cocked a long time. It loses more power the longer it's left cocked and if it's left cocked for very long periods the power loss is significant--25% is not out of the ballpark. The better the quality of the spring, the less the power loss is and the more it tends to "recover" after being left uncompressed for a long rest period. However, none of the springs recovered completely, no matter how long they were allowed to rest uncompressed.
Not to get too technical, but over compressing a spring will actually increase stiffness (otherwise known as "setting"), though most springs are designed to remain elastic even to its solid length so no stiffness change should occur. Springs that loose strength while remaining compressed is probably due to poor creep properties of the chosen material.
The experiment is repeatable--it's been repeated. With low quality airguns and springs and also with the best quality airguns and springs available. That includes high-dollar custom springs made to exacting specifications and made from the best materials available. The results are always the same. Leave them compressed and they weaken. Leave them compressed longer and they weaken more. The better the quality the less they weaken, but I have yet to see a test of a spring-piston airgun or airgun spring that didn't show loss of power from being left cocked.
I know what the theory says, but in the real world it just doesn't seem to work that way.
Oh I totally agree... I have seen airguns lose power after being left compressed, though mine have never lost power. I had a spring powered bolt action airsoft gun that chronoed 505fps when I built it, and after a 3 month storage with it accidentally being left compressed, still chronoed a solid 505fps. I just dont like the myth propagating that compressing a spring = less power. There are too many factors at work, which is why real life doesn't equal theory...
Well, it's not a myth that compressing the spring can cause it to lose power. No one here has said that compressing a spring always causes it to lose power.
Anyway, from what I've seen the more commonly quoted myth is that compressing a spring will never cause it to lose power.
Dunno anything about the guts of airsoft airguns nor whether their design is a good analog for typical spring-piston airguns.
jammin1237
New member
not that it really matters to the OP but i do have to ask.... the theories and testimonials from this thread all consider spring compression, have you all considered extending the spring for a given time and then using in said application? just to maybe see if it will give even more power?hmmmmm...
Its a spring piston setup, just with less power behind it.
Well I dont know about around here, but the airsoft forums I frequent, everyone thinks that leaving a spring compressed will reduce power. But all the repeatable tests with airsoft guns show that isnt the case. I dont have much experience with Gamo type break barrel pellet guns, so i'll try and keep my mouth shut where possible, but the blanket statement that leaving a spring compressed will reduce power just isnt true. I am not saying that leaving your Gamo rifle spring compressed will not result in lower power because there are always other factors at work...
Like I said before, plastic deformation of a spring will reduce fatigue life. More power in the short term, but will quickly die...
I may not be an aeropsace student, but I am a structural engineer and I respectfully dissagree (I'll bow to any mechanical engineers out there for a more authoritative opinion).
The true answer to whether a spring will loose strength over time is: No....but It depends on how you look at it. Your rifle will be weaker.
Obviously if you stress it beyond it's yield strength you get a plastic deformation and I'll assume that we are not talking about that here. What may happen, however, if the spring is stretched near yield, is "creep". Creep is a tendancy of any material to deform under stress over time. Creep is a science in an of its self but, in general, there is short term and long term creep and temporary (recoverable) and permanent creep.
Creep in steel is mainly dependent on material type, grains structure, temperature, stress, and time. Most importantly here, creep becomes measurable if the steel is stressed near it's elastic limit (near yield) and held for a period.
Now I said that it depends on how you look at it. The steel spring that has undergone creep has not actually lost strength, it just thinks that it's a different length. It will still follow Hooke's law, which states that the force a spring creates is proportional to the compression distance. However, after creep has taken effect, the compression distance has effectively changed.
Some the creep is recoverable and it will gain some strength back over time, but some will not and your rifle will be weaker.
The true answer to whether a spring will loose strength over time is: No....but It depends on how you look at it. Your rifle will be weaker.
Obviously if you stress it beyond it's yield strength you get a plastic deformation and I'll assume that we are not talking about that here. What may happen, however, if the spring is stretched near yield, is "creep". Creep is a tendancy of any material to deform under stress over time. Creep is a science in an of its self but, in general, there is short term and long term creep and temporary (recoverable) and permanent creep.
Creep in steel is mainly dependent on material type, grains structure, temperature, stress, and time. Most importantly here, creep becomes measurable if the steel is stressed near it's elastic limit (near yield) and held for a period.
Now I said that it depends on how you look at it. The steel spring that has undergone creep has not actually lost strength, it just thinks that it's a different length. It will still follow Hooke's law, which states that the force a spring creates is proportional to the compression distance. However, after creep has taken effect, the compression distance has effectively changed.
Some the creep is recoverable and it will gain some strength back over time, but some will not and your rifle will be weaker.