PDI 130 Spring too strong for FAMAS!

[Goge]

I just bought a PDI 130 spring and steel bushings for my brothers stock TM FAMAS. We swapped the stock spring for the PDI130, closed the mechbox and pulled the trigger. "Vrrrrrrr" Piston wasn't moving. Loading nozzel was going back and forth tho. Open it up, realign piston (was twisted off mechbox shell rails) close box and...

I can hear it catch the piston and draw it a little but then the gears spin and piston doesn't move. Looking inside again the gears were slipping off the piston, the piston was aligned but it looked like the motor didn't have enough power to pull it back so the gears pushed the piston "up" instead of back and started to just "scratch" the very bottom of the piston teeth.

Whats the spring limit on the FAMAS motor?
The PDI spring rating is only 320-350fps.

BTW replaced PDI spring with Stock spring and it works perfect again... so all we basicly changed was the bushings for him.

[ujiro]

I don't understand how it is pushing the piston off the guides though. If it pushed it off of the guides, it would be broken.

However, I have always heard that the V1 mechbox can't handle a stiff spring at all.

I still don't understand how the gears could be spinning but the piston not being engaged without the piston being stripped.

[CDN_Stalker]

PDI springs are crap, they have such bad consistancies from spring to spring (and Im talking about the same rating)................... I've had a handfull PDI 150% springs come across my bench, and they've been from 350fps to 425fps (and a pain to install), and different lengths too. The 350fps one I have is 6 3/8" long, most of the others were closer to 7", and had one that was right on 7" long. Nutshell, scrap that spring (any PDI spring is garbage that'll end up wrecking your gun), buy a Modify 90 from airsoftparts, install and have fun playing. That spring should keep you under 350fps (considering the long barrel in it), it nets me around 330fps in one of my MP5s.

[Goge]

Now that I'm thinking back, this spring seems stiffer then the one in my AUG that shoots just under 400... I can't set the PDI spring without someone's help but with the one in the AUG it's no problem.

I'll try one more time for kicks and if it's possible I'll take a picture of what happens. I think I'm gonna have to go with another spring tho.

[CDN_Stalker]

After I got my first one, all others I saw were a thicker and glossy black colour, and the lengths wildly varied form one to another. And I found it odd, the 170% springs were much softer than the 150% springs.

Go with Modify, they are cheap, extremely high quality and easy to get. Add in they are spongy and can be easily relied on for fps output................ can't go wrong there at all.

[Amos]

Originally Posted by CDN_Stalker

PDI springs are crap, they have such bad consistancies from spring to spring (and Im talking about the same rating)................... I've had a handfull PDI 150% springs come across my bench, and they've been from 350fps to 425fps (and a pain to install), and different lengths too. The 350fps one I have is 6 3/8" long, most of the others were closer to 7", and had one that was right on 7" long. Nutshell, scrap that spring (any PDI spring is garbage that'll end up wrecking your gun), buy a Modify 90 from airsoftparts, install and have fun playing. That spring should keep you under 350fps (considering the long barrel in it), it nets me around 330fps in one of my MP5s.

For the record PDI AEG springs are 100% different than their bolt action springs

[swatt13]

the famas being hitourque motor should be able to handle it

[Goge]

Solved...ish. Got the sector gear to grab the teeth of the piston after a reshimming. However the spring is too hard for the regular 8.4 I normally use in the FAMAS. It pulls the spring what sounds like maybe halfway before it stops. I can hear it trying but the spring/piston doesn't go and it won't shoot.

Using my brother's G3A3's 9.6 it will shoot and using the poor mans chrono (diet pepsi cans) it seems to shoot harder then my AUG shorty does. Crazy. Maybe I got the wrong springs in the package.

[Drake]

Sounds like a crappy PDI spring. I actually have a PDI 140% (from way back when PDI springs were actually okay) in a FAMAS and it works fine with a 8.4v 1500mAh large pack. The ROF was barely affected by the spring (it was "reduced" to about 950-1000 RPM).

If you have a super old FAMAS with the original EG560 motor that might be a problem, but with the newer (again, pretty relative; they switch to them in like the mid-90s) EG560HT (red label) it should work fine.

Also, the cylinder is shorter than a V2/V3 cylinder so be careful about adding too many upgrades with spacers (i.e., spring guide or piston head with bearings)