Umarex Umarex Zelos hammer spring

[LR_Plinker]

Hello great info... what is @.0.2" do you mean .02 " or .2 "

0.2" is 2/10ths, or 1/5th of an inch. If easier, in metric it would be @5.0mm

 

[Dwildemn]

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.

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Great information - attempting to tune my zelos for the first time. unaware of the oversprung problem. Have not moved my hamner spring yet but that was my next on my list. Got what I consider very good numbers for 155 bar and 25.5g .217 slugs. 7.03 spread @ 877. One mag only - afraid to try again! First time using nate chrony - didn’t know what I was missing. Anxious for my springs to arrive. Swore off aliexpress but made an exception for the springs. Thanks for sharing.