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Spring-Piston shooters: How often do you replace the spring?

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Scotchmo:
Better way to preset.

New spring
two foot section of 1/2-13 all-thread, two washers, two nuts.

Use the nuts and washers to compress the spring to coil bind on the the all-thread. Leave overnight. Removes from all-thread.

Install spring using the minimum amount of spacing to achieve the power needed. Don't cut the spring unless the power is significantly over the desired amount. Shoot a few hundred shots first. If FPE is still too high, cut a little at a time off the spring. If FPE us too low, space up the spring. If you need to space up the spring more than 1/4" or so, you probably should have used a spring with more coils.

When the power drops below what you want, change the spring.

gokidd:
PURE GOLD, folks!
Many, many thanks.
B

gokidd:

--- Quote from: c_m_shooter on October 20, 2017, 11:15:04 AM ---2 seasons on the HW97 factory spring so far.

--- End quote ---

Hi, Cliff.
Just opened up HW97 and it was broken about a coil and a half from the piston end.
One season did it for me.

I replaced the OEM spring with an ARH (Jim M) sub-12fpe unit, but haven't had time to test it on the chronograph. Shoots very smoothly.
Lessons learned: learn how to inspect your spring-piston internals, have some spares on hand and ... a broken spring still shot pretty dang well!
Bob

nced:
"How often do you replace your spring?"
Depended on frequency of shooting.............
I used to shoot about 10,000 shots per year but it's now about half that.

The spring itself..............
The last factory HW spring I used was with my .177 Beeman R10 and it was replaced before it broke after shooting about 5,000 shots. That was decades ago and that factory spring was replaced with a Maccari spring kit he called a "soft spring". That .177 R9 shot 20,000 mid weight pellets without breaking or sagging (judged counting empty pellet boxes and tins) and the velocity of the gun only dropped 10fps (7.9 grain from 910fps to 905fps). A few years ago I tried a Vortek PG2 kit in my .177 R9 and shooting 7.9 grain pellets the spring kit lost 80fps shooting less than one CASE (5,000 shots) of boxed Premiers. A couple years later I bought a bare Vortek spring and fitted it with a home turned spring guide and top hat and it was consistent up to 2500 shots power loss then a rapid decline in velocity.

The pellet weight.........
When living in West Virginia my brother used 10.5 grain boxed Premiers with his .177 R9 and I would replace a Maccari Tarantula spring about every two years. After a few years my brother found that the flatter trajectory of the 7.9 grain version trumped the greater resistance to wind drift of the 10.5 grain pellet and switched. After switching to 7.9 grain pellets a new Maccari spring never needed to be replaced while I still lived in WV (about 4 years).

Gun sealed and lubed properly.........
The gun needs to be sealed properly so the piston doesn't slam with the shot and lubed properly so the gun doesn't diesel with the shot which puts excess strain on the spring due to the piston rebounding rearward while the spring coils are still surging forward due to inertia. Part of all this is the fact that the spring strength needs to be "balanced" to the pellet. In the beginning I was trying to get 800 fps with a 10.5 grain .177 pellet from my R9 using an old design HW piston seal. Trying to do this I bought a heavy wire Maccari SteelGate spring (decades ago) and spaced the spring to the max, yet the highest velocity I could get was 780fps. After shooting for a while I took the gun inside and accidentally left it sit cocked for two days. When I did shoot the gun after that I noticed that it was still cocked and shot off the loaded pellet. Re-cocking the gun to load another pellet I noticed that the cocking effort was easier than when previously shooting so I sent the pellet over the chrony sensors. To my surprise the velocity was 790fps with the "sagged" easier cocking spring. That was when I had a practical lesson concerning balancing the springer power plant to accommodate the spring and pellet. LOL....a stronger spring might give less velocity than a weaker spring depending on the gun/pellet combination.

"Do you make that judgement according to loss of power or just age of the spring?"
As long as the trajectory is correct I leave the spring alone. When I start noticing a change in trajectory there will be a few shots over the chrony and the velocity will determine if the spring is to be replaced.
 
"do you "pre-set" your spring before using it?"
Nope because the first times the gun is cocked..........the spring is "set".

nced:

--- Quote from: Scotchmo on October 21, 2017, 12:21:37 AM ---Better way to preset.

New spring
two foot section of 1/2-13 all-thread, two washers, two nuts.

Use the nuts and washers to compress the spring to coil bind on the the all-thread. Leave overnight. Removes from all-thread.

Install spring using the minimum amount of spacing to achieve the power needed. Don't cut the spring unless the power is significantly over the desired amount. Shoot a few hundred shots first. If FPE is still too high, cut a little at a time off the spring. If FPE us too low, space up the spring. If you need to space up the spring more than 1/4" or so, you probably should have used a spring with more coils.

When the power drops below what you want, change the spring.


--- End quote ---

LOL.....like this made from threaded rod and flange nuts?............

I have used it a couple times with springs that needed "pre-setting", however I generally find it a waste of time and simply use my spring compressor to install the spring kit so the gun can do the setting...........

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