Nuprol Gun, Nuprol Springs - strange results.

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Pfc.Macdonald.J

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Evening. Excuse my unfamiliarity, but i've had some head scratching moments with some spring upgrade of late.

I recently bought a Nuprol Delta Recon Alpha, shoots at 320fps quite consistently. I fancied a few more fps to content with some .25s i want to use for windy outdoor games. So I ordered an Nuprol m110 and on swapping my stock out, expected to shoot around 360fps as advised. Shot 390 pretty solidly. Not to be discouraged, I got hold of a nuprol m100 and did the same. Shot at 390, solidly. Stumped...

Both new Nuprol springs measure a full inch and a half longer than the stock @approx 61/2' or 650mm, so when installed they are very compressed. The stock spring is shorter and therefore less compressed on install. 

Anyone have any nuggets of wisdom?

Anyone have experience upgrading a Nuprol AEG?

Used an Xcortech chrono .20g bbs on test 9.6v battery

 
The first thing that comes to mind is that they are both M110 and one was mislabelled

might be worth trying another M100?

 
newsh said:
The first thing that comes to mind is that they are both M110 and one was mislabelled

might be worth trying another M100?
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Definitely a possibility. 

Any thoughts on what made them shoot that fps though? It's high for those spring ratings no?

 
Pretty much every aftermarket spring I've bought has been longer than the stock one it replaces.

 
try a different brand spring. Supposedly the Nuprol AEGs are very efficient so science may make their springs perform better than they should but that makes no sense to me

 
Some possible scientific theory crap......

The springs are most likely under-rated

by that I mean they could be like Guarder SP100 Springs = a M110

(the rating is for 0.25's or they use the heavier bb when chrono)

So you probably got higher springs that you first thought on the box

Also from what I can gather the gun might have bearing/spacer on piston head

and very likely abearing quick change spring guide - these two will compress spring more

Thus will compress spring more = slight/moderate increase in fps

The box or guns do seem to have pretty decent seals - efficient or no real crap loss of fps

Also the gun's barrel seems to be about 363mmor a smidge over 380mm - not sure on exact length

but not losing expected fps like you can expect on shorter barrels sub 300mm

BUT - it appears to have a tight bore 6.03mm as standard so fps will creep up a little

Why both springs shooting the same fps ???

Yes could be the same springs - can/does happen mislabeling of springs

But - another factor is the bucking lips blowing out

Softer buckings or if the nozzle just about seals lightly then the lips can reach a point that they blow at

Not really experienced this myself but saw posts at Airsoft Mechanics about same fps on m120/130 etc....

shave tappet plate and/or harder bucking seemed to solve the under expected and similar power on heavier springs

BUT - you don't have to worry about this crap coz 390fps is above UK field limits

(just throwing a possible reason why both springs might be producing same results)

What you could try.....

On irregular springs:

Refit the original spring but instead of fitting tighter coils to back of box/spring guide

fit tighter coils up at piston/nozzle front of gearbox instead

fitting the spring ar$e about face should increase fps but only about 10fps I found

can't do this really if it is a regular spring

purchase say an Element M95 spring or SHS M100

though I have a gut feeling the SHS might be over

but the M95 might be OK for a while as the longer tbb but think the element springs fade a bit more

I'd try to refrain from spacing the spring or stretching the spring

spacing could be risky if the piston head spacer/bearing is getting close to bottoming out inside

You could put on a spacer ring/collar to spring guide like they sell/use on DSG's but only need a slight ring spacer

I'm guessing a 3mm to 5mm spacer aprox 15mm max outer diameter & whatever ID the spring guide is

can't be much larger OD coz inside of piston has to fit over this

(need to be very careful as stated the spring doesn't bottom out - I'd stick with say 3mm max (one extra tooth compression)

I'd get your hop set for decent quality 0.25's

Then I think you box has to be removed to do a quick spring change

so fit grip on box and get box working,

pop in ar$e about face original or m95 spring

with 3 pairs of hands try to prep hop/barrel with bb and chrono bare box/barrel

(will take a few attempts but you should get a decent idea @ chrono before you refit)

think you are looking at either trying say m95 or refit old spring in reverse perhaps to squeeze 10fps out

I tried to explain possible reasons why the higher than expected fps

and if springs are not the same why fps remains @ 390fps due to lips blowing maybe

as usual went right off on a tangent and by now most people are slipping into a coma reading this crap

hope some of this helps but most likely it doesn't - best of luck

 
if it is a V2 gearbox (which I imagine it is) changing the spring will be pretty much the same as most other M4's Have a look on YouTube for guides, there may even be one for your specific AEG

 
I thought the Nuprol Delta series had the quick change spring with the v2 gearbox? So wouldn't that be accessible from the rear stock ?

 
Cutrimson said:
I thought the Nuprol Delta series had the quick change spring with the v2 gearbox? So wouldn't that be accessible from the rear stock ?
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it does but annoyingly i think you have to take out the whole gear box to change it out... i took off the stock and everything but not even a standard spring will fit intot he tube

 
at least you don't have to split the gearbox! Getting a V2 box out is easy though, jump on youtube and do a quick search, loads of vids on it.

 
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