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.

I'd say to go with a Systema silent head set. It makes a huge difference as far as gearbox durability goes.

What is your reasoning for going with an Infinity Torque Up gearset? That's overkill. The PDI 170% I would highly recommend a gear set that increases torque levels, but infinity torque up is excessive. If your reasoning is simply due to Guarder's price point and the fact that they don't carry any torque levels in between, then I suppose that's fine. I'd still recommend you go with a Systema torque up or Prometheus double torque up gear set and maintain use of full-tooth pistons. (Half-tooth are required for infinity gear sets)

Yes, Systema piston heads are compatible with Guarder pistons. The fit may be a bit tight, but it'll work.


It's been tested and proven that aluminum piston heads will lead to catastrophic failure of the mechbox due to increased vibrational impact. Keep in mind the rigidity of aluminum. Compared to other metals (such as steel and titanium), it is VERY stiff and rigid and causes huge vibrational transfers through contacting materials. Aluminum piston heads are also heavier than synthetic (POM, silicon, polycarbonate) piston heads.
I was witness to a study that MadMax performed that proved these theories. The results of that study were never published, but the aluminum piston head was proven to be the worst piston head you could use if you were looking for durability.



Regarding the Pro-Win's enhanced air chamber seal - the increased seal won't be realized until you break the 450fps barrier.

I've used the following combination in my RPK with fairly good success and very little if no visable wear after 20K rounds. I was driving a 650mm tightbore, so some of the parts might be a little overkill for a 400fps setup. I'm not suggesting that you go my route as the spring/tightbore/bearing spring guide and piston head pushed the FPS up to the mid 400s, but just take a look and see what you can take for your own use.

Stock CA Ver 3 Shell
Prometheus Double Torque Gearset
Prometheus Bore-Up Cylinder Set (Bearing Piston Head)
G&P Polymidal Piston (Full Tooth)
Prometheus Bearing Spring Guide
Prometheus Anti-reverse Latch
Prometheus Tappet Plate
Systema M140 Spring

Cheers,
Vic.

Is a very good chance the gun he's using that spring in has a version 2 mechbox, since those are the only ones that break (yes, seen a couple V3 mechboxes break, but that is extremely rare) even with moderate upgraded springs (my PDI 150% destroyed my stock V2 mechbox within 2 months of basement shooting, not gaming since it was over winter, and the only upgrade was spring and bushings).

I would definately try to increase fps via effenciency (lower air loss) than running a stiffer spring then. I've seen a couple of broken V2 gearboxes and it's normally at the front of the cutout for the cylinder. Never a stock TM gearbox, but alsways one pushing a stiffer spring.

The quality matters because PDI has claimed that a 170 should produce 400fps, but they vary QUITE widely and are inconsistent. The other companies produce exactly what they claim.

I agree there. My MP5SD I got up to (I'd say unintentionally) 387fps. At first it sat at a pretty consistant 350fps, then I installed a bearing spring guide, went up to 365fps, then I installed a 330mm stock inner barrel into it (10cm above the 229mm that was in there) and that itself ended up adding another 20fps to tmy total.

I have a Prometheus 110SP spring in my other MP5, and aside from bushings is the only upgrade. Beginning of this year my SD tanked out of me withthe cracked mechbox (was shooting max 300fps), so I used my other one all year, about 15 or so games, and it shoots 365fps, still has the stock version 2 mechbox, and is running and shooting great. Case in point, Prometheus springs are very good even on stock mechboxes. And since my barrel is only 229mm in that gun, anything with a longer barrel and that spring will be sitting at a higher fps (and a lower chance of mechbox breakage).

Greylocks, that doesn't answer my question nor was it what I'm asking. pizzainthemorning stated that his PDI 170% is pushing 400+ fps in his ver 2 mechbox and was asking how to make it more durable while keeping a similar muzzle velocity. Some of the answers here were to change to a higher quality spring of the same FPS but if the spring outputs the same energy, how would that stop the mechbox from cracking?

That's a rather ludicrous statement. You're saying a high tension spring like the Guarder SP120 outputs less energy into your mechbox than teh stock low tension CA spring yet you get a higher fps?

The stronger the spring, the more damage it does to the version 2 mechbox.

Many points have been covered already this morning and Im not sure what I have to add. I will attempt to provide some insight as best I can as many have already stated helpful tid bits.

If you want keep that over 400 mark, I would say change the spring so something like a guarder sp100 or systema m120 and just upgrade your barrel, airseal nozel, and make sure youve got a good air tight hopup. But you wish to keep your PDI 170, so those options maybe out for you. However out of my two M4s, My M4 RIS has a higher FPS than my M4 MRE,My RIS has a guarder sp100 while the MRE has an sp110, but the RIS also has an upgraded deep fire airseal nozel and tighter barrel. So even though the MRE has a stronger spring, the RIS still has a higher fps due to having more efficient parts.

Unfortunetly my RIS also has an aluminum piston head on a systema red polycarb piston and aluminum cylinder head while the MRE is just stock piston head on a red systema polycarb with a stock cylinder for now, eventually my RIS may explode, it may not. I cant really say. As preventative maintenance I should replace just because.

The thing about reenforced mechboxes is that they arnt designed to last forever, they just take longer to break than regular mechboxes. Ultimately your goal should be to find appropriate parts that would compliment the other parts in reducing the stress.

Although if its in your budget and you can get one, a pro win mechbox may suite your needs if your goal is to continue running with that PDI 170.

Unfortunetly, unless I am blind, I did not see what type of aeg you are running this pdi170 in. If its anything wit a version 2 mechbox, well to be honest, I cant confirm this but some people just say v2's are garbage regardless how they are set up, thats not my opinion, just what some people have stated. I dont know, I havent had any major issues with any of my M4s. Nothing that wasnt fixable atleast.

Great guys, thanks for all the info so far.

It's a V.2 mechbox I'm running in my G3 as a sniper platform. FPS limits aren't really an issue because I likely won't be gaming on any fields with it. And in case you're wondering.... yes, cost is a factor (so no pro win for me, not now anyway).

Three things still though:

1. Spring Quality: Go with prometheus, or should systema or guarder be fine?

2. Piston: Aluminum or polycarbonate? I've read that aluminum ones can get chewed up leaving little bits of metal in your mechbox which isn't good.... but I've also read that they're more durable so I don't know what's going on.

3. About how much fps will a "silent" piston headset eat up?

Thanks,

Alex

if you are worried about the mech box exploding look for a mthaynes gear box. they are hard to come by but far superior.

I've had experience with Promtheus, they are damn good and pretty close to what the rating states (dependant on the barrel length of course.)

See about getting a King Arms Reinforced Mechbox from Jugglez (airsoftparts.com), they are about $40. I haven't tried them yet but I have four on order (two for a client, one for my MP5SD and one for stock)

Piston, stick with a polycarb one, it'll be nicer on your mechbox.

Piston head............. I've seen everything form 10fps to 30fps droppage in velocity.

If range is important to you (looks like it considering G3 as sniper rifle) you should go with what was mentioned above, get a 120 spring that is trustworthy, then focus on getting parts that'll make the airflow more efficient, such as piston head, cylinder head, nozzle, good hop up rubber (KN RH75 would be good for you, it's rated for guns 400+fps), and a tightbore (adds about 10fps). And use heavy BBs, no lighter than 0.28g.

If installed properly, none.

if you already have a bearing spring guide get rid of the bearing piston head. Its pointless and it will reduce the weight slamming into to your MB. Swiss cheese your piston to further reduce weight or start modding your piston head or/and cylinder head. Understand, these mods will reduce MB ware but there will be a FPS drop. You could use a SystemA silent head or bore up kit to pad your cylinder/piston head or an Angle head which use a form of an air brake if you don't want to do the mods. Air brakes are the most effective and they tend to quite your gun done too.

You can make an air brake
http://64.233.179.104/translate_c?hl...3DgJ0%26sa%3DG

or a padded cylinder head
http://64.233.179.104/translate_c?hl...3DgJ0%26sa%3DG
http://64.233.179.104/translate_c?hl...3DgJ0%26sa%3DG

you could also stretch for a CNCed MB.

Thanks guys, I really appreciate it. I think that's all the info I need.

Thanks,

Alex

For springs, I always either rock a systema m120, or a guarder sp100 or sp110. With either of those you will always be in good hands.

What makes me wonder is why 400fps is the magic number when I know MANY guns who shoot about 340-360 who are extremely accurate and durable.

Most anywhere, 400 is an upper safety limit, not a goal. A lower FPS lasts longer, is accurate if well done, and will not cost anywhere as much. Not to mention fewer headaches in upgrades.

But hey, what do I know, right?

Don't take it bad, but I think it's the first time I TOTALLY agree with Grey....
I am going at a game later tonigh with my 340 FPS G36K... accurate as hell...

range

Not that an extra 40-60 fps will carry your bb to the moon, but every bit helps.