Durability Desired, PDI 170
 

So I've been running my gun on a PDI 170 for a few years now and keep eating mechbox shells, gears, and pistons. I know, I should get it fixed up properly by a gunsmith, but that's not really an option. So, I'm ordering some more parts and was was hoping to figure out the following:
1. Will the parts be compatible
2. Will the parts be sufficient to run a PDI 170

Systema Reinforced Mechbox
6mm (I think) Steel Bushings
Systema Silicon Piston Head with Bearing
Guarder Infinite Torque Up Gears
Guarder Half Tooth Polycarbonate Piston
PDI 170 (of course)

Everything else on the gun is stock and has been fine thus far. I'm not looking for performance, just durability. I want a solid beast.

Will the systema piston head be compatible with a guarder piston?
Should the piston be half tooth, or will full teeth work fine also?
I've read good and bad about aluminum pistons... opinions?
Is a silent headset necessary, or will a silicon piston head be enough to prevent mechbox breakage?

Thanks,
Alex

anything will eventually shread under that spring...

only thing you can do? change the spring...

If the spring keeps on chewing your mechbox, the solution should be a no-brainer.
Get a far better quality spring.

Prometheus Ms120 will give you roughly the same fps but is far softer on your mechbox and its components.

Ya, get rid of the spring. Even my good PDI 150 (350fps) snapped my Hurricane reinforced mechbox after a while.

What is it about PDI springs that kill mechboxes anyways?

That being said go with a Systema or Madbull M120 spring. A silent head set is a good idea since you're running it in a V2 mechbox.

I gave guarder infinate torque up gears and you'll want halftooth piston. You may or may not have to shave down the trigger post to fit these!

PDI springs come in varying lengths (I've measured various 150% springs and found everything from 6 3/8" long to just under 7" long) and all are really stiff. It's odd but I've dealt with some 170% springs before and they are easier to compress than the 150% springs.

Yes a silent headset should really take some stress off the mechbox shell. Also a nice spring guide is in order, methinks.

Better quality spring, ok that's good to know. But I'd still like to keep it in the 400+ fps range, so a weaker spring isn't an option. If I go with a prometheus or systema M120 and those components would I be looking alright? (And I know anything will break eventually, but I'm looking for that general "safe bet")

Thanks,
Alex

That statement has always baffled me.

Will an aluminum piston head increase the spring/gun's power? Haven't compared weights, but for the sake of argument we could suggest the aluminum piston head is lighter than the polycarb one thereby having less inertia and permitting the spring to uncompress more quickly. The difference would be insignificant in terms of having a real impact on the mechbox's integrity.

Some people have also suggested it's the "metal on metal" impact that's damaging. Given equal amounts of energy and the soft nature of aluminum, I think it'd have to be tested. But even if that were true, the piston head never comes in contact with the mechbox: it impacts the cylinder head. So if there really is more wear from metal-on-metal impacts vs plastic-on-metal of equal force, the real part that should be avoided would be the upgraded metal cylinder heads, since they're what's pressed up to the mechbox and transferring the force of the impact from the spring/piston to the mechbox shell.

Long live good ol' Marui plastic cylinder heads.

See Lutnit's answer, and other spring brands mentioned. They are not weaker, just better quality control.

Why is a "better quality spring" easier on the mechbox? After all doesn't a Prometheus or Systema M120 (or whatever model fires 400 fps) have the same output energy as a PDI 170%? If it doesn't, how come these less energy springs are able to push BBs at the same level?

i just put in a guarder 120 spring in my M15A2 and im gettin 405 fps consistant and seems like there isnt as much pressure on the mechbox as the stock ca spring that was only giving me 320 fps

Agreed much better quality and less pressure = longer mechbox life

Just a quick note to add.

In my more recent builds, I've found that almost all M120 ~equivalent springs (madbull, PPA, etc...) have been resulting in velocities in excess of 400fps (i.e. 410-430). Might be just the combination of my builds, my chrony, etc... but it is what it is.

I've liked the madbull and PPA springs that I've used recently, but they've only been used for a season, so we'll see how they hold up. A Systema M100SS that I've had in an M4 for 2 seasons still shoots the same FPS since day one (est 27K-30K rnds).

If your local field limits are 400fps with 0.20g bbs...you may want to err on the low side (i.e. M110 spring or cut a couple of coils off a M120) and you should get your rifle chronied to be sure.

Not sure if everyone takes the field limits seriously, but I know that some do.

Well, I believe you forget that when you install a silent piston head, you need the corresponding silent cylinder head for the unit. Even the Angel Silent heads have a unique cylinder head IIRC.

There HAVE been tests done, I'll have to badger LUTNIT for the links again, where there has been shown up to 40% reduction in stress impact using the Angel Silent head ((I might be off on the figures here, recalling from reading this a year ago but it was significant)). The reason lies with material densities and how it all absorbs impact.



My question here is wether or not a pro-win's C&C shell would not be a better solution, if he REALLY needs such a high velocity that he's trying to get with this PDI170. IIRC that'd place him over 400FPS bending barrel. And with the better hop-up/mechbox seal of the pro-win, would he not be able to lighten the spring and get the same FPS he was shooting before?

Anyway, Drake an easy example as to why aluminum heads WILL hit harder and cause more damage, just think of a rubber mallet. If you're banging away at something that you don't want to "mark" but still need to hit the thing you use a rubber mallet. It weighs in at the same that its metal cousin does, but does not cause any surface damage. You're throwing both mallets at the same weight, same speed, same distance, and yet the rubber mallet does its job and does not leave marks, where the metal one will have clobbered the HELL out of what ever you threw it at.