Problem with FPS after spring change

[thehumanprimate]

Dear All,

A friend has just changed the spring on his son's M4, as it appeared to be 'hot' when using the coke can test - basically going through both sides, but not penetrating the bottom. Bought an M105(?) spring and did the replacement, cleaned the gears and used top quality silicone grease on the gears and piston slide put it all back together and its now ripping the bottom out of a coke can.

Any suggestion to what it could be? - I was thinking of the grease on the piston having a making a better seal, but even after emptying a few mags it still seems as hot.

Any help, suggestions, comments greatly appreciated

T

[Marksman1969]

Re: Problem with FPS after spring change

get it cronoed first - coke can isnt very accurate

[Caveira]

Re: Problem with FPS after spring change

What make is the gun? Sometimes they run very hot straight from the box, not only due to the spring, but also from the barrel and pistol seal.

If I had to make a guess, and it's only that, the gearbox may well have been so dirty it was restricting the speed of the piston as it released. Also, a good clean up of the barrel and hop will generally increase fps.

It could well be a matter of taking it apart again and trying the old spring. Also, if you can get someone local to chrono it, you'll know exactly how hot it is.

[Mitchmic]

Re: Problem with FPS after spring change

Hi,

Its my sons gun, its a brand new JG M4, the gearbox was full of nasty looking grease so i cleaned it out and replaced with the grease Tony mentioned.

I will get it tested properly and go from there but am fairly certain its above what it was before fitting the new spring :-(

Mike.

[Marksman1969]

Re: Problem with FPS after spring change

If it turns out to be like 10-15fps over the limit just fire a few thousand rounds through it - it will settle.

And as robin said JG guns are usually hot out of the box and most people fit lower powered springs and then find that after a few thousand rounds it drops even more ending up with like 320 but i find just put about 5000 through it and it usually drops just below the limit. (340/345)

[Chandler]

Re: Problem with FPS after spring change

my M4 JG was 400ish fps

Chandler

[The Keeper of Secrets]

Re: Problem with FPS after spring change

Are you sure of the spring that you put in? Chances are it's just another hot one.

[Mitchmic]

Re: Problem with FPS after spring change

Thanks, as i say i will get it checked and go from there.

The spring is a (quote) Element Airsoft AEG M105 Upgrade Spring, any thoughts on this type?

Mike.

[Fossilfuel]

Re: Problem with FPS after spring change

An Element m105 will give you 350- 380 odd on a version2 gearbox.

[Gaffa]

Re: Problem with FPS after spring change

Very good spring, use them in most of my guns..

They typically put out 340 - 350fps not 380 as stated above (M105 is short for 105 metres per second which is roughly 347fps).

Trust me, got these in 3 rifles, all chrono ranges from 340 - 350. (yes one's an M4)

[Fossilfuel]

Re: Problem with FPS after spring change

Strange how I've put them in 9 odd gearboxes recently (V2's, v3's and a V7) and most have come out way over 350 fps.


mind you they were mostly TM's so must have better airseals.

[Mitchmic]

Re: Problem with FPS after spring change

It did state 345 give or take so sounds about right Gaffa.

The coke can test is very rough and should not be used to determin FPS but i just worry that it is easily going through the bottom centre of every can (other than Pepsi!!) that i have tried!!

Mike.

[Mitchmic]

Re: Problem with FPS after spring change

Ok guys to close this.........

Had the M4 tested today at AWA and it was 390-395!!!! Doh!!!!

The nice guys in the Action Gamers tent put a M90 spring in that brought it down to 320 :-)

Mike.