Canted Spring - low velocity

[Basu]

My GenNex started hitting low at the target which I ignored initially.
The gun was very smooth as usual.
I was wondering as to why it was hitting low.
I checked the velocity by SimpChrony and found that it has lost 150 fps.
I opened the gun and then took out the piston.
Seal was perfectly alright and so was the spring, unbroken.
I noticed that I had pull the spring pretty hard to take that out from piston.
The spring was canted in either way and when cocked, it was giving pressure on ID of Piston , not allowing easy movement to produce full energy.
I changed the spring and the gun started giving awesome power.
Attaching pic.of canted spring.

Basu

[pratik_mahale]

After how many shots

[Basu]

After 1800 shots.
I suspect this started some 200 shots before.
Since the cocking was butterly ,so I had ignored that.
Now with new spring , it got back the power up to 7.4 fpe.

Basu

[avihkd]

Which spring hv u installed now?

[greenrifle]

Hello Basu Da,
Have you observed any new developments or betterment in GenNex... Do you think that spring lost power very early or the design needs some changes for this weapon.. happy Sunday and happy Shooting..

GreenRifle

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[Basu]

Dear green rifle,
The design of this AR is too good.
Maximum for a target shooter , a 100 gms increase in muzzle weight is recommended.
With new spring it got back it's power again.
This AR is sweetest .

Basu

[pratik_mahale]

That means Artemis may be having same problem.if you need to change the spring after every 1500 shot than its major reliability & consistency problem

[Basu]

Dear pratick,
I can not say about Artemis because I did not use for a long time.
My Sport does not have this issue so far , I wonder as to why it happened to GenNex .
I think quality of spring matters a lot.

Basu

[sam 47]

That means Artemis may be having same problem.if you need to change the spring after every 1500 shot than its major reliability & consistency problem

Sir,for Artemis, it is around 3500 shots, not 1500. It is more of spring sagging problem, where the spring shortens but remains relatively straight. I suspect pre-load & softness of spring to be the reasons but might be mistaken. I strongly believe that Artemis can gain much durability & maybe even little MV with a stronger spring.

[prashantjha19]

Dear Sam47,
Kindly allow me to invite your attention to this relatively old thread by Babu da.
Normally, how much of preload would you recommend if one wants a fairly powerful tune (of course one that does not mess up with accuracy)? I would assume some of it would depend on the inherent power of the gun, the spring tension, the mutual behaviour of the critical moving-friction parts like the piston, guide, etc.). But, given that one takes utmost care of these aspects to ensure smoothness, what do you suggest should be a recommended preload in a typical SDB power packed AR such as Artemis.
I am seeking your inputs in particular since you have made very insightful comments on Artemis, and been tuning and servicing your Artemis pretty dearly. I have also closely followed all your past inputs on this model and many other threads and have much appreciation for their candidness, clarity and logic.
I hope you will kindly find it worth responding on this rather very basic query please, and will look forward to your thoughts.
Best regards,
Prashant

[Basu]

Dear Prashant,
I am of the opinion that till date SDB is unable to produce a high quality main spring.
Having said so , Artemis has a 39 coils spring with wire dia 3.19 mm.
This size of spring does not leave much room for any preload.
I am afraid , with a more high reflex spring , it can cross 15-16 fpe.
With weight of only 3.2 kgs , this gun is already power packed.
It may have a capacity to deliver more but I seriously doubt the Performance in terms of accuracy with increased power.

Basu

[prashantjha19]

Thank you, Basu Da. I really think those (gun weight vs spring power) are very nuanced tuning factors - which only the experienced hands like you can read and feel. Thank yo indeed for pointing these out. Someone like me would have spent a whole year experimenting before realizing any such thing.

On the SDB springs, I would like to confirm this with you please - Is'nt SDB using the same spring in all its guns, only varying the length /number of coils and pre-loads in the different models?? Their product catalogue also lists just one spring. Do please confirm if this is not teh case.
I have heard though (I think from Sam47 on one of the threads on Artemis here) that SDB is in the process of designing a new spring for Artemis. Any clues /updates please?

Also, please do suggest a few HIGH REFLEX springs available around....so I could try some of these out and report back. Among the more popular local ones -G Smith, Precihole and Cherokee springs,- how does the REFLEX index play out please? I would think the G Smith one is the most TOUT (no idea of the reflex though), and the PH one is the most SPRINGY (if that is the right word please!!) Please do correct me.

Warm regards,
Prashant

[krishan.adhikari1]

Basu da, I have ordered the sdb genx from kovobazar. Do you suggest I should change the spring. Should I order the spring from kovibazar. Please suggest?

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[Basu]

@krishan
The spring of GenNex is quite good.
Anoop has gone past 4000 shots and still getting good power.
To replace the spring , you need to know the specification of stock spring​.
As regard to piston seal , SDB can only be replaced by SDB seals.
@Prashant
Again I must point out that Artemis is proportionately more powerful than it's weight.
A high reflex spring , such as Cherokee 27 , Gsmith or other, may generate some 50-60 yds of extra pace but again it will be trade off with accuracy.
SDB makes guns with different piston ID so they have different spring for each type of guns.
By using the word high reflex , I meant quicker recoiling quality.

Basu

[krishan.adhikari1]

@krishan
The spring of GenNex is quite good.
Anoop has gone past 4000 shots and still getting good power.
To replace the spring , you need to know the specification of stock spring​.
As regard to piston seal , SDB can only be replaced by SDB seals.
@Prashant
Again I must point out that Artemis is proportionately more powerful than it's weight.
A high reflex spring , such as Cherokee 27 , Gsmith or other, may generate some 50-60 yds of extra pace but again it will be trade off with accuracy.
SDB makes guns with different piston ID so they have different spring for each type of guns.
By using the word high reflex , I meant quicker recoiling quality.

Basu

Hi Basuda,

Received my Genex today. Shot it a few times from standing position using my dslr tripod.

Thanks for your suggestion.

Shot from approx 25 yards




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