Springs

[Aaron.l]

Hey guys,

 

Bought a specna arms sa e19 as my first airsoft gun from patrolebase. (I'm still noobish). Haven't had chance to play about with the hop up or optic yet.

Just wondering if anyone knows what spring is in it (I'm guessing m90) and what spring I can use for max fps based on the UK site laws.

 

Cheers

[Rogerborg]

Yes, it should be an M90, with a spare M120 in the box (although it may be in an opened "M90" wrapper).

 

The M90 should be usable, and notionally an M100 should get to close to UK limits.  However, it's entirely down to air seal and to some extend the BB weight you're using and whether your local sites chrono sensibly, or with 0.2g.  You may be lucky and get close enough as it is, or want a 95, 100, or 105.

 

I'd play with it first and see what it chronos at with the BBs and hop that you'll want to use, then take it from there.  A cheap chronograph will save you a wasted day if you come out a bit spicy.  It's easy enough to cut a spring down once you know what it's producing.

[Cr0-Magnon]

This is the weird thing about measurements in The UK. Springs are measured in metres but we chrono in feet. I have an aquarium, it's 4ft wide and holds 300L 🤔

[Rogerborg]

7 hours ago, Cr0-Magnon said:

Springs are measured in metres but we chrono in feet

 

Or in Joules. And Silverback springs are measured in Newtons.

 

Why can't we just all agree on a sensible value like ergs, or angstroms per femtosecond?

[Aaron.l]

Yeah I thought it was supposed to come with a spare spring but it didn't, thats what I thought was weird.

 

I read that the orion gearbox is supposed to mean I can change the sprung power without having to do any work on the internals, which is one of the reasons why I bought that gun.

If I'm using .25 bbs then is an m95 still probably over the 300fps or am I better aiming for an m100? I'm looking for ideally between 300 and the 350fps limit.

[#blackadder]

What Rogerborg said above ... You won’t know until you chrono it , with the bbs you will be skirmishing  . Borrow or buy a chrono - worth every penny . 

[ak2m4]

I would love to see springs measured in newtons at certain points of compression, this is what a spring factory uses and would save so much hassle.  A few screenshots from the spring factory where my ones are made.

 

 

 

 

[Rogerborg]

Indeed, I'm all for it. "M" ratings are intended to be helpful, but given the wide range of variables (air seal, cylinder to barrel ratio, BB mass) they're really just a relative scale, and only within a manufacturer's own range.

 

The Silverback springs just give a single Newton value - I'd assume (by which I mean hope) that it's at the compression of a fully cocked and locked SRS or TAC-41.

 

Even at that, with a 100N spring in mine, it doesn't feel like I'm lifting 10.2kg to pull the bolt.  Hmm, that would actually be measurable though... 🤔

[EDcase]

As Roger said, the fps for a particular spring depends a lot on the gas flow efficiency so you can never say exactly what fps you'll get with a certain spring.

 

I've made a simple contraption to measure spring power in Kg which will help get an idea of the fps you'll get from your particular rifle.

PM me if you want to buy one (£10)

Edited April 19, 2022 by EDcase

[Francosonny1120]

Classic army m24 ltr is amazing stock for anyone looking for a cheap alternative, not fully upgradable tho so don't expect some insane performance after upgrades.. nice exterior too.

[Tactical Pith Helmet]

12 hours ago, EDcase said:

As Roger said, the fps for a particular spring depends a lot on the gas flow efficiency so you can never say exactly what fps you'll get with a certain spring.

 

I've made a simple contraption to measure spring power in Kg which will help get an idea of the fps you'll get from your particular rifle.

PM me if you want to buy one (£10)

A gunsmiths trigger pull tester is very similar. 

[EDcase]

1 hour ago, Tactical Pith Helmet said:

A gunsmiths trigger pull tester is very similar. 

Yeah, same principle I guess.

It does work quite well and testing a few springs you can make a chart of Kg vs resulting fps for a particular rifle.

With enough samples from various rifles it should be possible to predict rough fps in general.

[ak2m4]

8 hours ago, EDcase said:

Yeah, same principle I guess.

It does work quite well and testing a few springs you can make a chart of Kg vs resulting fps for a particular rifle.

With enough samples from various rifles it should be possible to predict rough fps in general.

 

I built myself one of these a couple years ago, handheld not fixed, but every time I pulled back a spring it gave different reading.  Do you get much variation in readings?

[EDcase]

16 minutes ago, ak2m4 said:

 

I built myself one of these a couple years ago, handheld not fixed, but every time I pulled back a spring it gave different reading.  Do you get much variation in readings?

It varies by a few grams each time.  I pull to a marked line then press the 'Hold' button to save the reading so I don't have to look at it while pulling.

[Rogerborg]

 

On 19/04/2022 at 10:53, Rogerborg said:

Even at that, with a 100N spring in mine, it doesn't feel like I'm lifting 10.2kg to pull the bolt.  Hmm, that would actually be measurable though... 🤔

 

Well, shows what I know.  Using a cheap and admittedly uncalibrated luggage scale, with a Silverback 100 "Newton" spring with about 4 loops cut off, I'm seeing a 17kg (166N) peak from a slow, careful pull, and nearly 25kg (245N) peak from a more realistic sharp pull.

 

It still doesn't feel anything like that, mind, because it's a short, smooth pull.

 

Makes me want to try a Rapax 2J+ spring which claims a lighter pull for the same boing.  Out of stock at Skirmshop, of course. £21 delivered from Serbia... except if I get mugged for VAT, and the mugging to pay for the VAT mugging.