Can pellets be too heavy for a springer?

[Buldawg76]

Hector
That's kind of what I was thinking with the Vortek outer guide inside the piston but was not aware that it could work just as well without the top hat since I thought the top hat ( at least the steel ones ) where not only to center the spring but add some weight to the front of the piston to reduce bounce back that you have described here and allow the spring to live a longer and happier life. I was not aware the top hat being adhered by a small amount of grease to the front of the piston had that much of an effect on bounce back from the suction that the grease has on it.

I am interested in how the beehive springs work in a spring gun since as we have discussed here about the big difference in length versus diameter between engine springs and air gun springs. It will be an interesting experiment to see if the reduction in harmonics and fatigue gained in a engine is also transferred to the same design spring in an air gun. Inquiring minds want to know. 

I do think I have some issue inside the 48 that is causing the piston to have hard contact with the compression chamber when fired like the seal is not standing proud enough of the piston to absorb the pistons impact with the end of the chamber without hard contact. It shoots JSB 10.34s at 870 fps so its not leaking compression at all. I have not had time to tear into it to verify my preliminary diagnosis as of yet. After the two scopes it broke were sent back to Hawke they called and offered me an upgrade to a Airmax SF 30mm tube for only pennies more so naturally I jumped on it but that scope went on my Mrod FT gun since it was just to nice to go back on the 48 and honestly I did not want to break it until I can confirm my suspicions of the piston making hard contact with the chamber.

I was told by the Hawke rep that called they would still continue to honor their lifetime warranties on all scopes regardless of what gun they were mounted on and would replace the varmint scope if I did not want to upgrade. He also recommended that if the scope was going on a spring gun regardless of low or high power that Hawke advises to use a 30mm scope instead of the 1 inch models. So before a scope goes back on the 48 it will be inspected as you say for damaged seals and repaired accordingly.

Mike   

[Rocker1]

Built many many engines for some extremely top names in racing, used many beehive springs, mostley for clearance, we could use higher lift cam profiles without coil bind. remember the lifter follows the cam and its not as violent as you would think, big difference in a ten inch spring and a 3 inch spring when it is compressed. David

[Buldawg76]

David
Agreed on the beehive springs and higher lifts achieved but a valve spring opening and closing at 10k rpms is quite violent albeit at a very short distance as compared to an air gun springs long compression range. Especially if its a hydraulic lifter since the cam profile is very steep on the initial opening ramp to set the lifter into the hydraulic lock situation it needs to open the valve with the least amount of loss of lift, solids are not near as aggressive on the opening ramps.  Each has it own parameters it must live in to survive.

Mike

[HectorMedina]

Hector
That's kind of what I was thinking with the Vortek outer guide inside the piston but was not aware that it could work just as well without the top hat since I thought the top hat ( at least the steel ones ) where not only to center the spring but add some weight to the front of the piston to reduce bounce back that you have described here and allow the spring to live a longer and happier life. I was not aware the top hat being adhered by a small amount of grease to the front of the piston had that much of an effect on bounce back from the suction that the grease has on it.

I am interested in how the beehive springs work in a spring gun since as we have discussed here about the big difference in length versus diameter between engine springs and air gun springs. It will be an interesting experiment to see if the reduction in harmonics and fatigue gained in a engine is also transferred to the same design spring in an air gun. Inquiring minds want to know. 

I do think I have some issue inside the 48 that is causing the piston to have hard contact with the compression chamber when fired like the seal is not standing proud enough of the piston to absorb the pistons impact with the end of the chamber without hard contact. It shoots JSB 10.34s at 870 fps so its not leaking compression at all. I have not had time to tear into it to verify my preliminary diagnosis as of yet. After the two scopes it broke were sent back to Hawke they called and offered me an upgrade to a Airmax SF 30mm tube for only pennies more so naturally I jumped on it but that scope went on my Mrod FT gun since it was just to nice to go back on the 48 and honestly I did not want to break it until I can confirm my suspicions of the piston making hard contact with the chamber.

I was told by the Hawke rep that called they would still continue to honor their lifetime warranties on all scopes regardless of what gun they were mounted on and would replace the varmint scope if I did not want to upgrade. He also recommended that if the scope was going on a spring gun regardless of low or high power that Hawke advises to use a 30mm scope instead of the 1 inch models. So before a scope goes back on the 48 it will be inspected as you say for damaged seals and repaired accordingly.

Mike

I am glad you are getting a good service from Hawke. I was not so lucky.

If your piston seal is good, check your breech seal by MAKING ABSOLUTELY SURE THE GUN IS UNLOADED AND UNCOCKED and blowing with all your strength into the barrel. IF air escapes, even slowly, then you need to replace that seal (make sure that air is not escaping between plastic muzzle piece and barrel).
Also the tightness of the closure. Cocking lever should stop about 1½" from closure and the rest should be closing pressure. Depending on the seal you are using closing force may be higher or lower, but the distance to closure is pretty much uniform.

IF you still think that it is a question of hard contact between piston and compression chamber end, then I would have to wonder if that contact is on the first compression cycle or on subsequent ends of bouncebacks (the first one being the most important, of course), and then the ONLY way to reduce that, if you have tried all other possibilities, is by using a lighter pellet.

Good luck with your 48! Indeed 870 fps for a 10.3 grainer is an excelent power level.

Keep well and shoot straight!



Hector

[Smoketown]

If you don't want to put your mouth over the muzzle, you can use a length of rubber heater hose over the end of the barrel for the same effect.   

Cheers,
Smoketown

[Buldawg76]

Hector and Jim

I have the delrin breech seal or whatever material it is that ARH sells for the 48 in it but have not tried the pressurizing the breech seal that way to test for leaks, I have done the tissue paper test and see no movement from it when firing. No front sight just a muzzle weight/brake with factory shroud in place.

My cocking lever is preloaded about 1 1/2" from closed so I believe its closing tight. I hear what sounds like a metal to metal clank noise when shooting but cannot tell if its on the first compression cycle or second or possibly third.

So just need to test breech seal and if its good then take it apart and see if seal is proud of piston nose or not and see if any evidence of hard contact. 

I have COPD so not sure if I can create enough pressure on the breech seal myself but have a large syringe I can rig up a fixture to use it to pressurize the breech seal and determine if it leaks down or not.

Mike