Airsoft Forums UK

AND then sit around waiting for the next god knows how many mths before you can actually use it at a game ? 

But if you get the 621 sorted - that's a QC box

Meaning it can be a "spring tester" gun

if/when you rebuild the 516 gun

Drop the ol' 516 spring in, test out the fps

then see what you might need/get on a new spring

before reassembling the std 516 box

Springs are funny bastid's

so many factors come into play to get 349.99fps

a short gun tends to have say a m115 spring

& longer guns say m95 spring

then it depends if there are any spacers & crap inside piston

includes bearings inside adding 5mm extra compression

or spacers - 5mm plastic in G&G cheapies

to 9mm alloy spacers in basic cheapy Chinese guns

A piston's tooth is 3mm pitch

so 9mm alloy spacer in say Cyma piston

can add up to say 3 x extra teeth compression/power/energy

(but with shit seals you'll lose a fair bit of this)

However factors like above with chunky spacers

plus bearing spring guide - or std non-bearing spring guide

all this throws a bit into the mixture when testing spring/fps

(plus poor seals and joule creep on longer barrels etc...)

LUCKILY - the 621 & 516 seem to be similar length barrels

so you could use the 621 to roughly test the old 516 spring

and guesstimate what you might expect with decent good seals

and the appropriate spring (of a sort) with a chrono etc...

As the 621 with stock tube off takes like 30 secs to change spring

= a half decent gun to test out any springs you might buy

some springs have tighter coils at one end

and usually the tighter coils go at the back on spring guide

however if you flip the spring (tight coils up front)

you "may" see a slight increase of say 10fps

other springs you may see no difference if you flip

them, but on the "irregular" springs with tight coils one end

you might be able to very slight boost/reduce fps by flipping it

Still handy to have a QC gun to test/compare springs

even if you are experienced in guessing the springs power

(it is still a guess - no matter how experienced you are)

even the spring test is ONLY a ROUGH EXPECTATION

as you fit the same m100 spring into 3 different/length guns

and you could easily get:

300fps in a MP5k (141 barrel)

328fps in a M4 Carbine (expected on 363 barrel)

356fps in a AK47 (455 barrel)

or anything around these very very rough estimates

depending on spacers & quality of compression/seals

So at times - trying to gauge what the fps might end up being

can be a bit of guesswork to say the least

well the genuine cyma pistol mag came and well.........the mag catch aint catching so will have to open it up and find out wats the problem im guessing its going to be a spring issue lol

think that will be more what needs done for the 621 if im honest as that did feel under powered when i shot it and did get one chrono off it at 200 odd so think its going to be more the 621 thats gonna need the work as i have chrono'd the 516 its hitting the 315-305 mark off the bat on the nihm batts which im happy with so thats going to stay like that for now when it breaks may throw in a cheapish fet that has precocking as the 516 is a little shorter barrel length at 280mm so could use it for a cqb m4 once i change the handgaurd when the little man aint using it idealy if i could get a 2nd v2 box like in the 621 to throw in the 516 id do that rather than any other upgrades but even a non fet v2 box is near 40-50 sheet

@druid yup but ill have it all dialed in for when we do so not messing about trying to dial everything in on my first skirmish i have a 35-40ft personal indoor range for now possibly away to convert my attic into a range/pistol cqb area for me and the kids get couple low power aeps to have fun with when i aint shooting targets haha

Thing to remember they are both

or the 516 is a very basic cheap starter gun

and nothing really will change that

YES you can fit fancy mosfets & upgrades to it

(your gun - your choice)

but though you can tweak it quite a bit

and take it quite a way

be careful you don't end up fitting a £1,000 ICE

into a £600 Fiat Punto

or a stfu cruise control system into a Mini Metro

(showing my age)

get gun running, tweak on a budget

and save the money perhaps for a slightly better gun

that said plenty also like to go nutz making insane sleeper guns

but I'd just do stuff in stages as & when required

reckon new piston & good compression you'll be golden for a while

aye im not gonna go mental on it tbh i have took on board the stuff said on the 621 thread ,im pretty sure i seen a 20-30 if not chaper fet that has the precock just cant mind where from lol

totally get ya bud was like me throwing hundreds at a £1800 new on the road motorbike i had

aye im not planning on spending nymore than 40 on the 516 when it breaks so as i only really have around 20-30 invested in both guns from buying em so that would equate to of buying the gun new lol if goes over that then its no bueno lol

yeah im not a sleeper fan i just want to make them as reliable as possible so am listening to what you guys say and not going in madly on em like i originaly wanted to lol

i am thinking of building a dmr similar looking to this https://www.patrolbase.co.uk/cyma-cm-072-mk12-spr-mod-1-custom-w-fullstock?pv=3704  

but building from scratch of course find a metal receiver i like and decent v2 box and go from there  but im a long way off from that hahaha  thats me just dreaming for now