What Spring / Motor Combination for CQB

[bas1xx]

hi,

I own a Krytac trident mkii crb...

I am running asg 40k motor with sp120 spring with an 11.1v for outdoors.I'm wanting to play CQB where the limit is 328 fps but an allowable limit of 350fps.I am from the UK so in my spares I have the stock m100 spring and the stock 20k motor.Can I swap the spring back to the m100 with the 40k motor and a 7.4v battery, or will I get PME? - as I know with m100, 40k motor and 11.1v  I'll get pme.if not for cqb ill have to put it back to stock.
 

 

[Sitting Duck]

a sp120 is a guarder sp120 = m130 = 425fps

a reg m120 = 396 aprox, maybe a smidge lower for a 280~300mm barrel

a sp120/m130 is a bit much to use as is

a m120 could be short stroked 3 teeth but more involved

a m105 might be a smidge too high @ 344.4fps, minus a bit for a 280~300mm barrel

could drop to say 330fps but risks being a bit hot if limit is 328fps

so the stock spring might be best

though if irregular type spring...

the tighter coils on left go on the spring guide

but if you flip it you "should" increase fps by about 10fps

(just in case the fps is a bit lower or higher if you fitted it incorrectly)

so you got a possible 10fps to play with

change spring to stock one...

40k / 18.65 = 21.5 rps aprox on a m100 could be say 23rps - a bit risky if going nuts on full auto maybe

question is is it double firing on semi ???

if yes then change motor

20k / 18.65 = 11rps & run on 11.1v (11 x 1.55) = 17~18rps

if gun is seriously precocking on semi with 40k motor deffo change back to 20k

but 20k is a bit lame, a better motor would have been a 30k but hey ho

but you don't run the 30k krytac motor @ 350fps on 11.1v coz double firing/pme risk

30k / 18.65 = 16.1rps on 7.4v & on 11.1v = 25rps+ on 350fps so getting to 27rps on a 320fps gun

(or more if m90 spring krytac often installed, hence many uk spec krytac's didn't like 11.1v if a 30k import motor)

so 30k on 11.1v is faster than a 40k on 11.1v - so would be worse than your 40k example

the gun talks to you - if it starts to double fire then it's saying you are pushing it too much

can get it running with short stroking but more work etc....

double firing or over spin can be a worn Cut Off Lever but often a sign is running too quick

in "theory" you should just be OK at around 22rps on a stock gun (just)

but might not hold up long term if going nuts on full auto after a while

(stock piston wearing etc.. AoE blah blah blah, but it is better built than some guns when pushed a bit)

Finally as you are likely to be single shot only it is unlikely you will rip the crap out pushing it a bit on semi

if you was spraying & praying on full auto then yeah it will wear more I expect going through mags (and the piston)

It really depends on the fps/spring, if the 40k is 40k or a mental 45~50k motor etc....

if you are pushing a 300fps gun then yeah use the slower motor or a 30k max motor or something

(the rps will increase a bit on a lower m90 spring but pme risk is 20rps than say 23~25~27rps etc...)

So really, chuck in m100, fire a few single shots on semi and see if she double fires

the c rating of 7.4v is hopefully 20c than a 40c, and capacity is about 1500mah

a 30c 3000mah packs more punch than a 20c 1500mah and this can alter expected rps

so hard for to say for certain if it will be OK, it is pushing it a bit but should just about be OK

(if you don't go nutz too often)

Battery being used, actual spring (not just the fps but spring itself as you could have a leak)

true real speed of motor (and its max possible speed), the ratio of gears - assume 18.65:1)

so there a fair amount of possible rps together with spring being used

which means it is difficult to give you a 101% answer...

I think it will just about be OK, to use for semi cqb

BUT - YOU must confirm it isn't double firing on semi

it will precock a fair bit though but just about below pme threshold

HOWEVER....

FFS use QUALITY BB'S, you do not want feed issues, or a jam at speed....

if you get a jam don't go nuts on full auto trying to clear it - use the jam rod

if you full auto a jammed bb, the blockage will slow the piston return like pumping a syringe

(or testing compression), which will result it piston not returning & PME stripping stuff inside

a faster motor like the 40k will drain battery quicker and pistol grip gets a bit warmer

hence many go for a 30k aprox over a higher speed motor like 40k+ ones

(next time go for a 30k than a 40k)

 

[Rogerborg]

I think the honest answer is: you'll have to try it and see.  As Duck says, I'd expect double firing on M100, 40K and what I'm going to guess is a pretty meaty 11.1V, let alone PME.

You're going to need to put the M100 spring in anyway, and swapping motor and batteries takes seconds, so why not just fire in and let us know how it turns out?  Actually, depending on your air seal and barrel, you might even have to drop down to an M90, as I've just had to do with a well sealed 229mm 6.02mm ZCI barrel that was seeing 374fps (!) on an M100.

Have you already got it locked to semi?  I ask because if that M120 spring is putting out over 375fps on full auto, that's a Section 5 firearm, not an airsoft gun.  And no "but I won't switch it to full auto, honest" isn't a defence.

Aside, there's a Technical / AEG section which is better for questions like this: https://airsoft-forums.uk/forum/27-electric-guns/

 

[Adolf Hamster]

11.1v and a 40k is pme central at 1j, i would very seriously suggest slowing it right down and looking at a mosfet to make up the difference with precocking.

the slower gun that runs all day is more useful than the super speedy gun that blows up halfway through the first round.

 

[bas1xx]

Alright sounds good guys. by the sounds of it for cqb I'll drop in the stock set up and then for outdoors remain with what I've got. and then look into upgrading the mosfet in my gun to a gate titan in the coming months.

Full auto isn't an option on the gun as its locked out and quite frankly I don't agree with full auto spam either.