GAMO SPRINGS - AAAARRRRRGGGGHHHH!!!!

[vinceb]

I had put a virtually NEW Gamo spring (came out of my refurb 440 that I believe was a cosmetic return - just about 11" long, I know it was a low-mileage spring!) into my Shadow.

OK, OK... I know I must have overdid the lube a bit - but after shooting several dozen shots, nice'n quiet, it decides to diesel ONCE on a CPL. Broke the sound barrier, of course - and lost about 40 FPS in the process.

This is the THIRD time I've had a Gamo spring lose substantial power after one or two diesel shots. NEVER had any OTHER damage to the piston, chamber, or seal. Just the spring, and ALWAYS the spring.

I think I'm gonna order a bunch of Quest springs and tophats. They should be at least as durable as the spring in my B19 at least - 3 years and many thousands of pellets, and it runs faster now than it did when new. And they are actually available (imagine that)!

[daved]

Hey, Vince, don't you mean detonate rather than deisel?  Granted, I'm pretty new to the "adult" air gun scene, but my understanding is that all springers deisel.  It's inherent in the design, and is partly responsible for the ability of our current crop of rifles to shoot at 1000+ fps.  When a gun deisels, the high powered compressed air causes the tiny amounts of lube in the gun and on our pellets to burn.  This has the effect of increaseing the power.  When a gun detonates, that same lube explodes instead of burns.  This is what results in pellets going supersonic, and springs bending or breaking, as well as other damage.  All of which is why you NEVER want to introduce any sort of volatile lube in the barrel/chamber of a high powered springer.  I don't have the link handy, but the Pyramid Air Blog has an excellent article on this very subject.  If you're interested, I'd be happy to chase it down for you.  BTW, I get a lot of deiseling from my CFX when I shoot RWS Superdomes, must be the pellet lube they use.  Doesn't seem to be nearly as noticeable with anything else I've tried.  And beleive me, I've tried a lot!  Later.

Dave

[vinceb]

Technically speaking, dieselling merely means "compression ignition". A burn can be initiated by a diesel event, and then progress into detonation if the conditions are right.

In any case, this is not what happened. The gun had recently been lubed, and had several dozen shots through it before this happened. I'm reasonably certain that the combustion wasn't severe, since neither the seal nor the chamber was damaged.

You have to remember that these guns - without dieselling - often dance on the edge of supersonic. A mild amount of dieselling might be all that's required to give the pellet an extra 100fps - but that could be the difference between a nice, quiet shot and one that brings the cops out!

I don't believe that modern, synthetic-sealed guns really rely on burning lubricant for power. A few months ago I did a test on my fairly healthy .22 cal B-19... I stripped it down, completely degreased it, and reassembled it with nothing more than dry moly powder as a lubricant. The gun lost less than 20fps, and that could easily have been due to higher drag on the sliding parts because of the lack of a liquid lubricant.

There's really no reason why Superdomes should be especially prone to dieselling... and I really doubt that RWS uses a combustible lube on the pellet! Really heavy pellets are sometimes more prone to it, as their higher inertia means that a higher pressure builds up in the compression chamber. But Superdomes aren't that heavy (8.3 gr, if my memory is correct). If the gun is still going supersonic, you're still dealing with excess lube inside the compression tube.

The way gamo greases every thing it could be a problem, when the rifle is fired and the compression piston stops all the grease keeps going forward and ends up in the bottom of the piston and slips by the seal.

 Gamo has the knack for taking a chunk out of the seal when they assemble the rifle which lets the grease into the compression chamber and Bang goes the rifle.

[Gene_SC]

Maybe that is why I have never had a bad spring or problem with any of my Gamo's. When I buy them, I clean up the barrel and put maybe a half tin through the rifle and then send it to CDT for professional tune. Not that other guys can't tune them but I know that CDT does it by the book. He completely disassembles the rifle and washes all the parts up before he starts, while constantly using his air hose to blow any left over shaving's off.

I could go on an on about the detail he puts into these air rifles, but ya all, already know how it is done.

So far I have not had a problem with spring or any parts failing with any of my Gamo's and I have eight of them that I constantly shoot. Cost me a small fortune for pellets....

Good Luck Guys

Gene

[vinceb]

Spring (C1K177-010), tophat (C1K77-005) and seal (C1K177-002)... about $10 + shipping

The spring fit snuggly onto the guide, and the seal was a perfect fit. After a few dozen break-in shots, the gun now shoots CPL's in the 920's -930's with no more twang.

Can't wait to see how it holds up over the long term...