Specna arms H-05 FPS issue

[Delgado900]

Hi guys,

Starting a new thread on this.

I was impatient waiting for Patrol Base to have the Specna Arms H-05 in stock so I ordered it from Gunfire who were super quick.

I knew I would have to change the spring to lower the FPS (spare spring in the box stating 310fps). So I changed over the spring and it felt a bit weak, chrono’d it and it was running at 285fps hop was fully on so expected it to be lower than 310fps.

So I read somewhere that the lowering spring was a m90 spring. So I thought I’d pop out today and buy a m100 spring to increase the FPS to hopefully around 330-350fps. Changed over the spring now I’m at 405fps ..... help 

 

[ak2m4]

What spring brand was it?  Sounds to me like you may have a M120 there but each brand is different in how they rate springs.

What FPS were you getting before you changed to the included M90?

Worth checking the hop chamber and bucking for any misalignment / damage.

 

[Delgado900]

It’s firing straight as anything. 

Before lowering to the m90 spring it was firing at 430fps 

so the spring i went out any purchased today was an SHS m100 but the spring tension between the two were polar worlds apart so I’m thinking that the spring may have been packaged incorrectly. 

Any way to determine a spring from the coil rotation pattern? 

 

[ak2m4]

I've noticed this with SHS springs now and then.  M110 tend to go M100 packaging and in some M110 you find M120's.  M110 and M120 look very similar,

Post a pic of the spring and I'll see if I can eye-ball it for you.  I've spent so long looking and testing these springs lol

 

[Delgado900]

Ok so the attached photos 

shs m100 that feels super toight 405fps

Then we have the spring that came installed which was chucking out 430fps 

I’m going to run it at as is on Sunday and will take my old faithful rifle just in case 

View attachment 45479

View attachment 45480

View attachment 45481

 

[ak2m4]

Definitely a M110 or a M120 buddy.  If you want I can send you a ZCI M100 out today which are dead on from my tests.  Should get to you tomorrow ?

 

[Delgado900]

Ahh man I felt like it was too tough putting it in ! 

Oh you hero, how much do you want for it? 

 

[ak2m4]

Just £5, have sent you a PM with details

 

[Delgado900]

Spring received, will post FPS results later!  Thanks @ak2m4 

 

[Delgado900]

Ok so.... drumroll 

spring changed 343fps 

happy with the results ?

View attachment 45533

 

[ak2m4]

that is perfecto ?  

 

[Daveoc33]

Having this exact same issue. Really helpful thread. Thanks both of you! Spring ordered @ak2m4

 

[Lozart]

Two things here - 1) the "M90" spring that comes with the Specna is made of Dairylea, 2) Pete @ak2m4 is a bloody star.