Umarex Umarex Zelos hammer spring

Jump to latest Follow Reply
N

nobody1

Member
Sep 4, 2021
932
742
WA, United States
UPDATE
Instead of the 9mm OD spring I started using the 8mm OD spring.
The 9mm OD spring was rubbing against the hammer which caused inconsistent velocities, a 30-40 FPS spread.
The 8mm does not have the rubbing issue.

Original post
I have got my Umarex Zelos .22 caliber a few days ago.

The original hammer spring is too strong to get a good tune.
When you increase the hammer spring the velocity usually drops a few FPS.
This is with the regulator at 1750-1800 PSI.

These are the OEM hammer spring dimensions:
Length: 63.5mm
Outer diameter: 8.5mm
Wire diameter: 1.2 to 1.3mm (coils are too tight to measure accurately)

I have managed to use a different hammer spring I bought from Aliexpress:

I bought the springs with these specs:
Outer diameter: 9 mm RECOMMEND the 8mm OD
Wire diameter: 1.2 mm
Length: 100 mm

I have used the 9mm OD spring (cut at different lengths) in the SPA PP750 and the Umarex Notos.

For the Zelos I have ended with the above spring cut to about 56-58mm length.

In the photos bellow the OEM spring is on the left and the spring I used is on the right.




20240918_134524.jpg20240918_134503.jpg20241004_220221.jpg
 
Last edited:
  • Like
Reactions: silverstreak, Gramps, Firewalker and 1 other person
nobody1 said:
I have got my Umarex Zelos .22 caliber a few days ago.

The original hammer spring is too strong to get a good tune.
When you increase the hammer spring the velocity usually drops a few FPS.
This is with the regulator at 1750-1800 PSI.

These are the OEM hammer spring dimensions:
Length: 63.5mm
Outer diameter: 8.5mm
Wire diameter: 1.2 to 1.43mm (coils are too tight to measure accurately)

I have managed to use a different hammer spring I bought from Aliexpress:

I bought the springs with these specs:
Outer diameter: 9 mm
Wire diameter: 1.2 mm
Length: 100 mm

I have used the same spring (cut at different lengths) in the SPA PP750 and the Umarex Notos.

For the Zelos I have ended with with the above spring cut to about 56-58mm length.

In the photos bellow the OEM spring is on the left and the spring I used is on the left.

There is another discussion about the Zelos hammer spring here: https://www.airgunnation.com/threads/zelos-hammer-spring-adjustment.1319310/

View attachment 497334

View attachment 497335
Click to expand...

Thank you sir!!
 
  • Like
Reactions: nobody1
Upvote 0
Stubbers said:
That ought to do, trial and error my friend!

I would heat up the cut end and then close it with a pair of needle nose personally, and maybe sand/grind it flat like OEM.


-Matt
Click to expand...
I cut all my springs with a rotary tool and use the same cutting wheel to flatten and polish the cut end of the spring.
 
  • Like
Reactions: Firewalker and Stubbers
Upvote 0
With the regulator set at 2000 PSI and with the above hammer spring cut to about 56 mm I get a range of 780 FPS to 930 FPS with Norma 17.6 grain pellets.

The 780 FPS is with the hammer spring guide flush with the end of the receiver.
The 930 FPS is about 4 turns in.
If I go to the end (about 6 turns in) the velocity drops to about 910 FPS.
 
Last edited:
  • Like
Reactions: Stubbers
Upvote 0
nobody1 said:
With the regulator set at 2000 PSI and with the above hammer spring cut to about 56 mm I get a range of 780 FPS to 930 FPS with Norma 17.6 grain pellets.

The 780 FPS is with the hammer spring guide flush with the end of the receiver.
The 930 FPS is about 4 turns in.
If I go to the end (about 6 turns in) the velocity drops to about 910 FPS.
Click to expand...

Found the plateau and can tune down to 780 fps, really good data points for those that want to achieve similar, good work.

-Matt
 
Upvote 0
I am at about 890 FPS now at 2 turns in.

I tried 1.5 hammer spring turns in from flush (about 875 FPS) and 2.5 turns in (about 895 FPS).
Both of those were louder, which usually means less efficient.
No idea why the 875 FPS at 1.5 turns was louder than the 890 FPS at 2 turns in.

I am getting 60-65 shots from about 3600-3800 PSI down to 2000-2200 PSI.
 
Last edited:
Upvote 0
nobody1 said:
UPDATE
Instead of the 9mm OD spring I started using the 8mm OD spring.
The 9mm OD spring was rubbing against the hammer which caused inconsistent velocities, a 30-40 FPS spread.
The 8mm does not have the rubbing issue.

Original post
I have got my Umarex Zelos .22 caliber a few days ago.

The original hammer spring is too strong to get a good tune.
When you increase the hammer spring the velocity usually drops a few FPS.
This is with the regulator at 1750-1800 PSI.

These are the OEM hammer spring dimensions:
Length: 63.5mm
Outer diameter: 8.5mm
Wire diameter: 1.2 to 1.3mm (coils are too tight to measure accurately)

I have managed to use a different hammer spring I bought from Aliexpress:

I bought the springs with these specs:
Outer diameter: 9 mm RECOMMEND the 8mm OD
Wire diameter: 1.2 mm
Length: 100 mm

I have used the 9mm OD spring (cut at different lengths) in the SPA PP750 and the Umarex Notos.

For the Zelos I have ended with the above spring cut to about 56-58mm length.

In the photos bellow the OEM spring is on the left and the spring I used is on the right.




View attachment 497334View attachment 497335View attachment 501952
Click to expand...
I just "rediscovered" the Zelos over sprung problem. Decided to shoot 15.89 JSBs and wanted to tune down to around 900 fps. Dropped reg pressure to about 1800 psi and got speed down to about 925 - 930 fps. Tried to adjust the HS and found that more pre-load consistently dropped the velocity 2-3 fps per half turn. I have some decent calipers and get the following dimensions for the OEM spring.

Length - 63.5 mm
OD - 8.48 mm
Wire Dia - 1.17 to 1.19 mm (not 100% consistent diameter)
Guide Rod Dia - 5.46 mm

Thanks for the link to aliexpress. I chose to order the 1.0 mm diameter wire spring in 70 mm and 80 mm length with 8 mm and 9 mm OD. I saw your cut down 1.2 mm spring and offer the following thoughts.

I believe the 1.2 mm diameter wire is likely too large. The OEM spring is too heavy and the wire diameter is slightly under 1.2 mm. The spring rate is primarily determined by the wire diameter, secondly by the OD, and lastly by the number of coils (length).

I believe you would be better off using a lighter gauge wire (e.g. 1.0 mm ) in full length or slightly longer. With a too short spring and the hammer adjustment backed all the way out, the hammer will not be under tension at the end of its travel when it hits the poppet valve stem. This may result in less consistent opening and dwell time for the poppet valve. This is the logic/rationale for me choosing the 1.0 mm wire in slightly longer than OEM length.

I believe the poppet valve will give more consistent opening and dwell time with the hammer under spring force over its full travel. This should give lower variance and standard deviation in pellet speed and lead to better accuracy. The extra length spring gives me plenty for trimming to fine tune the preload force.

I have some experience with spring rates and tuning pistols for peak performance. I operated a custom gunsmithing shop from 1990 to late 2002 specializing in 1911/2011 Limited and Open Class pistols for the USPSA crowd. I was (emphasize was) a GM competitor in Limited Class before I went over to the Middle East in March 2003.

It will take a couple of weeks for the springs to arrive and figure which spring gives the best range of adjustment in the hammer spring. I'll post results when I've got the Zelos tuned up.
 
  • Like
Reactions: bernieorosz and nobody1
Upvote 0
DSLeach said:
I just "rediscovered" the Zelos over sprung problem. Decided to shoot 15.89 JSBs and wanted to tune down to around 900 fps. Dropped reg pressure to about 1800 psi and got speed down to about 925 - 930 fps. Tried to adjust the HS and found that more pre-load consistently dropped the velocity 2-3 fps per half turn. I have some decent calipers and get the following dimensions for the OEM spring.

Length - 63.5 mm
OD - 8.48 mm
Wire Dia - 1.17 to 1.19 mm (not 100% consistent diameter)
Guide Rod Dia - 5.46 mm

Thanks for the link to aliexpress. I chose to order the 1.0 mm diameter wire spring in 70 mm and 80 mm length with 8 mm and 9 mm OD. I saw your cut down 1.2 mm spring and offer the following thoughts.

I believe the 1.2 mm diameter wire is likely too large. The OEM spring is too heavy and the wire diameter is slightly under 1.2 mm. The spring rate is primarily determined by the wire diameter, secondly by the OD, and lastly by the number of coils (length).

I believe you would be better off using a lighter gauge wire (e.g. 1.0 mm ) in full length or slightly longer. With a too short spring and the hammer adjustment backed all the way out, the hammer will not be under tension at the end of its travel when it hits the poppet valve stem. This may result in less consistent opening and dwell time for the poppet valve. This is the logic/rationale for me choosing the 1.0 mm wire in slightly longer than OEM length.

I believe the poppet valve will give more consistent opening and dwell time with the hammer under spring force over its full travel. This should give lower variance and standard deviation in pellet speed and lead to better accuracy. The extra length spring gives me plenty for trimming to fine tune the preload force.

I have some experience with spring rates and tuning pistols for peak performance. I operated a custom gunsmithing shop from 1990 to late 2002 specializing in 1911/2011 Limited and Open Class pistols for the USPSA crowd. I was (emphasize was) a GM competitor in Limited Class before I went over to the Middle East in March 2003.

It will take a couple of weeks for the springs to arrive and figure which spring gives the best range of adjustment in the hammer spring. I'll post results when I've got the Zelos tuned up.
Click to expand...
I found the springs were cheap enough on AliExpress I bought 0.8, 1.0, 1.2, 1.4 and 1.5 wire in a bunch of different lengths. That way I usually have several around the range of the OEM spring. Or a long one I can adjust to length. When I pull one of my guns apart because I'm bored I'll swap springs just to see the effect. Write the data down and decide if a different spring is better.

I'm not one that worries too much about tuning my rifle. I just like seeing the effects and studying the engineering.
 
  • Like
Reactions: OldVet, nobody1 and Perle
Upvote 0
I was successful at getting my Zelos tuned. From the factory, the hammer was definitely over sprung. I ordered several different spring from AliExpress and the one that worked the best is a carbon steel (not SS) spring with 1mm wire diameter, 8mm coil OD, and 70mm length. Link below.
Replacement Hammer Spring

I did need to trim a couple coils off the 70 mm spring and then stretch slightly to the OAL of the OEM spring (65mm). My first attempt with the Reg pressure set to 1800 psi and 19 coils on the new spring turned out to still be over sprung. My second attempt with Reg pressure at 1600 psi worked out much better. The attached EXCEL spreadsheet jpeg snip shows the average velocity for each 1/2 turn in on the hammer spring adjuster starting from flush with the back of the receiver. I got a definite knee in the graph of velocity vs turns-in. I backed the hammer spring adjustment screw back out to be 3 full turns in from flush. This gave me about 910 fps. Accuracy was excellent with a single ragged hole for a 5 shot group.

I also tested my new moderator after getting the rifle tuned. Very happy with the new moderator. Completely eliminated the bark to the point that the loudest sound is now the hammer hitting the poppet valve. The rifle is now very backyard friendly. The moderator did shift my POI 1/4 - 1/3 inch down at 15 yards which is to be expected.

Overall, very happy with the rifle and the tune, All testing was done with JSB Exact Jumbo .22 cal 15.89 gr pellets.

AliExpress Spring.JPG


Zelos Tuning Snip.JPG
 
  • Like
Reactions: grouch-o and xsarfc9x
Upvote 0
I am new to this conversation, but I have been playing with a .25 Zelos for a little while now. The biggest improvement I have been able to get out of the gun came after I changed out the valve spring for something softer. I also made a new spring adjuster, but the same results can be had from removing @.0.2" from the OEM part.

I have been working on two tunes for the gun, one for pellets, one for slugs. (I ordered a second Zelos before the first one even shipped - but now have my doubts about that first one actually getting here - ordered from DACK before reading the horror stories). The pellet Tune had me reducing the reg to @1900-1950psi, used with zero preload on the hammer spring. In fact, I can slip a credit card between the hammer face and the valve pin. The result is a much quieter shot cycle, zipping Hades down range at @ 910-915fps. With 4 simple baffles installed in the shroud, and the softer hammer hit it reduced the sound output by @30db 6-8ft from the gun. The reduction is really noticeable in the breech area while shouldering the gun.

Bumping the reg pressure up to @2400psi and turning the new spring adjuster in @ 2-2.5 turns (remember, I removed @0.2inches from it) I am getting 905-908fps with ZAN 33grn slugs.

I made the spring I am using in the valve body, but have ordered several off the shelf pieces to try. If I find one that gets the same sort of results I will post a part number for it. I am using 0.017" wire down from the stock @0.042".

Fun gun. It has proven to be very accurate with ammo it likes.
 
Last edited:
  • Like
Reactions: Perle
Upvote 0
LR_Plinker said:
I am new to this conversation, but I have been playing with a .25 Zelos for a little while now. The biggest improvement I have been able to get out of the gun came after I changed out the valve spring for something softer. I also made a new spring adjuster, but the same results can be had from removing @.0.2" from the OEM part.

I have been working on two tunes for the gun, one for pellets, one for slugs. (I ordered a second Zelos before the first one even shipped - but now have my doubts about that first one actually getting here - ordered from DACK before reading the horror stories). The pellet Tune had me reducing the reg to @1900-1950psi, used with zero preload on the hammer spring. In fact, I can slip a credit card between the hammer face and the valve pin. The result is a much quieter shot cycle, zipping Hades down range at @ 910-915fps. With 4 simple baffles installed in the shroud, and the softer hammer hit it reduced the sound output by @30db 6-8ft from the gun. The reduction is really noticeable in the breech area while shouldering the gun.

Bumping the reg pressure up to @2400psi and turning the new spring adjuster in @ 2-2.5 turns (remember, I removed @0.2inches from it) I am getting 905-908fps with ZAN 33grn slugs.

I made the spring I am using in the valve body, but have ordered several off the shelf pieces to try. If I find one that gets the same sort of results I will post a part number for it. I am using 0.017" wire down from the stock @0.042".

Fun gun. It has proven to be very accurate with ammo it likes.
Click to expand...
Hello great info... what is @.0.2" do you mean .02 " or .2 "
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu