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

[gokidd]

Hello, folks:
I ask this question here in WFTF looking for guidance from the shooters who strive for maximum performance from the spring guns.
How often do you replace your spring?
Do you make that judgement according to loss of power or just age of the spring?
Also, do you "pre-set" your spring before using it? (Probably the wrong term, but I'm asking about putting a new spring under tension for maybe 30 minutes before you begin using it.)

Best wishes,
Bob who wants to be WFTF next season

[c_m_shooter]

2 seasons on the HW97 factory spring so far.

[canadian_shooter]

 I would have to say if breaks or substantial drop in power. I have 2 steel spring guns and 1 gas spring. Both of the steel spring guns are over 30 yrs old and have shot many thousands of pellets. I recently fired both over a chronograph and they are still within 20 fps of original. (my Slavia 630 [570fps with 8 grain ] and Webley Hurricane [428 fps with 7.4 grain]

[Sfttailrdr46]

Unless you leave it cocked sitting in a closet for months or the spring breaks as already stated not to worry. When the spring in my D460 broke near the top hat there was a significant drop in power. My 8.34 JSB 's dropped about an inch at 10 yards

[Motorhead]

Presetting is a GREAT idea ... assemble gun, cock it and place it in a corner for a day or 3 ... Cycle a few times & chrony ... take back apart and shim spring for the power you want.
In time you see a drastic velocity shift ... RESPRING TIME !!

[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]

2 seasons on the HW97 factory spring so far.

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]

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.

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...........

[gokidd]

Thank you, Ed. I know you are keen on spring-piston and I appreciate you sharing your experience.

Bob

[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.

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...........

If you want maximum power, don't bother presetting.

If you want maximum life, preset as I described.

If you spaced the guides up so that the spring is nearly coil bound when it is cocked, than external presetting won't likely help anything.

[nced]

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.

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...........

If you want maximum power, don't bother presetting.

If you want maximum life, preset as I described.

If you spaced the guides up so that the spring is nearly coil bound when it is cocked, than external presetting won't likely help anything.

Please explain how "pre-setting" (pre-sagging if left over night) makes a spring last longer.

The first thing I did to my new .177 R9 and new .177 HW95 was de-tune the guns to shoot CPLs at 850-860fps. To do so I make the spring kits based on the Maccari E3650 with no "pre-setting"........


Here is a home spun spring kit from my HW95........


Anywhoo.......Maccari springs without pre-setting have maintained set power longer than the Vortek springs I've used so I'll skip the "all-tread and nuts" unless absolutely necessary for an exceptionally long un-set spring!

[Mole2017]

I may switch my Gamo back to a spring, and I don't plan on any presetting. I wasn't long into this air rifle for pest control than I figured out I was better off leaving the gun cocked and loaded. If I took a shot, I cocked and loaded right away before moving in for a follow-up. If no follow-up needed, I put it away as it was. None of this shooting off a perfectly good pellet...

4000 rounds it was before that spring broke, and I think it actually shot pretty well with a broken spring too. Only when the broken ends got out of line, so to speak, and dragged did things get crunchy on the cocking cycle and erratic when shooting. Mind you, it wasn't like every shot went bad, just every now and then something weird happened.

Anyway, my advice would be to not stress out about presetting. Decided if you like them sitting around cocked or not and just use them. Figure out if the gun likes a few warm up shots or not (mine never needed them). Pay attention to shifts in point of impact and such and you'll do ok. Nothing but a failure changes very quickly. Even your own shooting can shift and evolve (or devolve).

[WyoMan]

Please explain how "pre-setting" (pre-sagging if left over night) makes a spring last longer.

Sorry to butt-in but the answer is simple...
Pre-setting a spring (coil-bind) will shorten the spring length while leaving the spring constant the same. So you get a spring that is under less load when cocked.... and yes, the stored energy is reduced. But less load means less stress on the steel. Less stress means more cycles before fatigue failure. And cocking a springer does not pre-set the spring with the same amount of plastic deformation as the coil-bind example. Unless the cocking takes it to coil-bind...

Wyo

[Scotchmo]

...
Please explain how "pre-setting" (pre-sagging if left over night) makes a spring last longer.
...

Assuming that the cocked gun is not close to coil bound - If the non-preset spring takes a set when you first cock it, you have exceeded the yield strength of the spring. Every time you subsequently cock the gun, you are running it right up to the yield point.

If you preset it to coil bind before you install it, you are establishing a new coil spacing. And a stress level which you will never reach again. So when that spring is installed, you are staying somewhat below the yield point when cocked.

Lower cyclical stress = longer fatigue life. But it also means less energy for any given spring.

[nced]

...
Please explain how "pre-setting" (pre-sagging if left over night) makes a spring last longer.
...

Assuming that the cocked gun is not close to coil bound - If the non-preset spring takes a set when you first cock it, you have exceeded the yield strength of the spring. Every time you subsequently cock the gun, you are running it right up to the yield point.

If you preset it to coil bind before you install it, you are establishing a new coil spacing. And a stress level which you will never reach again. So when that spring is installed, you are staying somewhat below the yield point when cocked.

Lower cyclical stress = longer fatigue life. But it also means less energy for any given spring.

Thanks for the feed back! I have a couple new Maccari springs and since I never tune my HW springers for full power anyway, think I'll try "pre-sagging" one of the E3650s and install in my HW95 to see how it works.  LOL.....this will certainly make it easer to get a proper spring guide fit without needing to compensate for the "coil diameter expansion" of a new spring after it's set.

[nced]

...
Please explain how "pre-setting" (pre-sagging if left over night) makes a spring last longer.
...

Assuming that the cocked gun is not close to coil bound - If the non-preset spring takes a set when you first cock it, you have exceeded the yield strength of the spring. Every time you subsequently cock the gun, you are running it right up to the yield point.

If you preset it to coil bind before you install it, you are establishing a new coil spacing. And a stress level which you will never reach again. So when that spring is installed, you are staying somewhat below the yield point when cocked.

Lower cyclical stress = longer fatigue life. But it also means less energy for any given spring.

Thanks for the feed back! I have a couple new Maccari springs and since I never tune my HW springers for full power anyway, think I'll try "pre-sagging" one of the E3650s and install in my HW95 to see how it works.  LOL.....this will certainly make it easer to get a proper spring guide fit without needing to compensate for the "coil diameter expansion" of a new spring after it's set.

Over night I set a new Maccari E3650 spring (35 coils of .120 wire wound with .515 ID) to "coil bound" for 12 hours using the "threaded rod and nuts".
Here is the result......


Notice that the spring set "coil bound" for 12 hours is only 1/4" shorter than a different E3650 that was set simply by installing in the HW95, cocking, then shooting a few groups.

I am surprised that the Maccari spring was so straight after removing from the "rod and nuts" considering the squirming from side to side the spring endured while tightening the nuts.

I haven't cut new fitted guides for the "compressed by coil bind" spring yet but that will be the next phase of testing.
Anywhoo......I'm skeptical that the extra 1/4" of pre-set achieved by "coil binding" will be much different than simply "setting by cocking" but I may be surprised! 

I also realize that I've only "messed with" one spring for one gun, so perhaps different springs will react differently. I do know that even when "setting by cocking" the two Vortek springs I used sagged quickly after 2500 shots unlike the Maccari springs that have maintained velocity much longer. Matter of fact, my first Maccari spring kit bought a couple decades ago for my .177 Beeman R10 was "retired" after 25,000 shots (determined by counting empty pellet tins) and the 7.9 grain CPL velocity was still 905fps after starting at 910fps several years prior.

[gokidd]

One piece of science-free experience, here.
My freshly-installed sub-12 fpe kit from ARH showed 11.9 fpe on my HW97.
About 300 pellets later, it is now 11.5 fpe.
I did zero presetting. Just shot the gun.
No power spacers installed with the kit, just the ARH top hat and guide.
Thanks,
Bob

[gokidd]

One piece of science-free experience, here.
My freshly-installed sub-12 fpe kit from ARH showed 11.9 fpe on my HW97.
About 300 pellets later, it is now 11.5 fpe.
I did zero presetting. Just shot the gun.
No power spacers installed with the kit, just the ARH top hat and guide.
Thanks,
Bob

I realize this post is ancient by Internet terms, but here's one additional thought to share, in case it might be helpful.
The ARH kit performs really well for my needs.
I suspect that one reason the kit needs to settle-in with a few hundred pellets is the extremely tight fit of the ARH spring guide.
This could be another good reason to do a "presetting" of a new spring kit.
BOINGERS UNITE!
;-)
Bob