My gun rings like a bell after every shot

[steverebo]

So I have done a few upgrades on my arp9 and now when I shoot it rings like a bell. I have had a couple of full day skirmishes and it was a pleasure to use but this ringing is really annoying me.

The changes I made were a new compression set

stock cylinder short stroked 13:1 gears M120 spring with a coild and a bit removed 

Rocket bearing spring guide 

Stock motor 

155mm prometheus barrel 

 

[snuff]

Seriously I had this on my Specna,I took it apart to no avail.I adjusted the hop and it fired ok but still rang.I eventually discovered that I had bent one of the 3 tangs on my flash hider.I actually liked it tbh.

 

[steverebo]

Mine sounds like it's coming from inside the gearbox I think I might be the spring because the gears are shimmed to perfection the motor height is spot on

 

[johnnyj]

Does it have bearings on the piston also? 

When you clipped the spring did you clean it up correctly? ( spring is what I would be looking at tbh)

 

[steverebo]

Yes piston has bearings, when I clipped the spring I heated it till red hot pushed it against a flat surface so it flattened out a bit and then I sanded it so it wasn't totally round

 

[johnnyj]

I would personally remove 1 of the bearing sets from the gun ( piston to make it lighter ) 

 

[steverebo]

How much would my fps drop if I remove the bearing

 

[Adolf Hamster]

You could try a different spring, something longer with a bit more compression at rest.

Otherwise precocking will effectively prevent the "boioioioing" after firing.

 

[steverebo]

You could try a different spring, something longer with a bit more compression at rest.

Otherwise precocking will effectively prevent the "boioioioing" after firing.

Just tried with precock still does it it's definitely the spring I can hear a ting after each shot.

Precock does reduce it slightly 

 

[MagpieTactical]

Pull the charging handle and let it go, does it do the ringing noise? If so, try putting grease on the spring for the charging handle. It was this on my G&G guns that made the ringing noise. 

 

[Badgerlicious]

Try putting grease on the spring for the charging handle. It was this on my G&G guns that made the ringing noise. 

That and the forward assist spring. 

 

[MagpieTactical]

That and the forward assist spring. 

Never considered that one.  Just roll pin out and then the button followed by spring? 

 

[steverebo]

So I have completely removed the upper reciever to rule out the charging handle and forward assist and it still rings and I am even more confident that its the spring.

I have found a plastic washer on my stock arp9 piston head so u could remove the thrust bearing and use this instead 

 

[ak2m4]

Try some grease on the spring itself.  Additionally whenever I've removed the bearing from the piston head I always notice a 15 - 20fps difference with 0.2g

 

[The Waco Kid]

Check the flash hider isn’t loose or not aligned. They make a nice ring when they vibrate.

 

[Rogerborg]

If the spring is loose on the guide, some heat-shrink can snug it up.

 

[Floperator]

Very unlikely that the spring is ringing out, it's under compression and in contact with the piston and compression chamber. Though spring guides and top hats are always a good idea.

I'd be looking at the flash hider or outer barrel.

 

[Lozart]

stock cylinder short stroked 13:1 gears M120 spring with a coil and a bit removed 

Very unlikely that the spring is ringing out, it's under compression and in contact with the piston and compression chamber.

As the OP has cut the spring down, there's every possibility that the spring is NOT under compression at the end of a cycle.

@steverebo - if you open up the gearbox, with the piston and spring guide in place, is the spring under tension when the piston is fully forward or can it move freely back and forth?

 

[Floperator]

As the OP has cut the spring down, there's every possibility that the spring is NOT under compression at the end of a cycle.

@steverebo - if you open up the gearbox, with the piston and spring guide in place, is the spring under tension when the piston is fully forward or can it move freely back and forth?

Didn't imagine that the OP would have cut the spring down to negative preload, would expect a massive loss of FPS if this was the case.

If so then a tophat and/or spacing washers would fix it. Or new spring lol

 

[Lozart]

Didn't imagine that the OP would have cut the spring down to negative preload, would expect a massive loss of FPS if this was the case.

If so then a tophat and/or spacing washers would fix it. Or new spring lol

If it was an OEM spring they are often shorter than an aftermarket spring anyway.