Lets talk Pistons

[Rabbit]

So I just set myself back a good deal of cash picking up an XCR - I'll now be eating cans of beans and mr noodles till next pay.

Working on a VFC 416 everyone always said the first thing to go would be the clear plastic piston - i'll be facing this with the XCR, so i'd rather replace it and possibly the spring (I heard XCRs come with m120s) all at once.

Lurking recent posts by Maciek & Stealth Lonex seems to be the brand of choice by the technologically advanced gundocs - although reading about their pistons they seem to have fitment issues with certain popular brands of AEGs.

With graveyard posts as well as my own expirience i've always known the Modify Hi Speed (white poly carb) piston as the go to brand of replacement - although I have really messed up some gearsets with the black Quantum piston by modify.

What else is there? I'm just looking for durable replacement for the VFC clear plastic one. I expect to be shooting around 375-380fps and keeping everything else internally stock.

[lurkingknight]

the goto piston used to be the shs 14 tooth metal rack, but they've encountered some oddball issues in the recent batches like offspec tooth locations.

The SHS 15 tooth is fine, just grind off the first tooth to make it a 14.

The lonex is a good choice, I've never used one yet, but I hear really good things about it.

Aside from that, I have 3 CA blue poly/fiber pistons with metal racks, all modified down to 13.5 teeth. About 45k rounds through all 3 guns and no issues.

[Thenooblord]

I always go for plastic tooth pistons, if theres a jam, I'd rather just replace a $20 piston than $100 gears, modify polycarbonate ones are good

[iKliiu]

If you get a Lonex, make sure to swiss cheese it. Also, Lonex pistons have troubles with certain sector gear brands. SHS 15 tooth are nice, as well as their 7 tooth.

Also, try to get a nylon-polyamide piston instead of polycarbonate. POM is also a good option.

[Off_kilter]

I've found polycarb based pistons have a tendency to crack. I'd stick with polyfiber/nylon based ones.

Also $100 for gears is rediculous...unless they're seigetek cnc gears with i've never heard of breaking.

[Adamlxlx]

TM piston. Used one for almost 6 years hardly any wear.

[ThunderCactus]

prometheus, I've never had one fail on me, or in a customer gun in hundreds of thousands of rounds
Catch is, you HAVE to use them with prometheus gears

[lurkingknight]

Polycarb as a material is great for impact resistance... it does not do well with stretching and shearing; it's a bad choice for pistons.

[Styrak]

Originally Posted by Thenooblord

I always go for plastic tooth pistons, if theres a jam, I'd rather just replace a $20 piston than $100 gears, modify polycarbonate ones are good

Modify pistons are the worst pistons I've seen. A lot of the pistons I've replaced that have been stripped are Modify purple pistons.

[lurkingknight]

Originally Posted by Thenooblord

I always go for plastic tooth pistons, if theres a jam, I'd rather just replace a $20 piston than $100 gears, modify polycarbonate ones are good

As an aside my shs gears cost less than my Ca pistons.. 19$ gears vs 25$ piston... shs 15 tooth might be closer to 10$ though.

If I'm paying 100$ for gears.. you better bet I'm buying siegeteks

[Cobrajr122]

Stock TM Piston.

I went to replace mine after 4 years just cus I thought it would finally be time, opened it up and VERY LITTLE wear at all. They are beasts.

[SF_Chewy]

Never get the purple Modify pistons. I had one bnib and it shattered after 200 rounds. Its a cheap polycarb piston. However Modify Ultra High Speed (the white one) is not bad, I've had one in one of my guns for a few years of hard use before I had to replace it. Bad BBs caused a jam and stripped it. Its really been one of my goto pistons.

I've also been running the SHS 14 tooth piston in a high speed setup with little to no issues. I would say correcting AOE and shimming counts more with using full metal teeth racks.

Also the stock Mariu piston is actually a pretty good for a stock piston. I'm using one in a medium speed build and it is holding up beautifully. Only mod I did to it was shaving off the first tooth and some of the next two teeth.

[MaciekA]

Originally Posted by Thenooblord

I always go for plastic tooth pistons, if theres a jam, I'd rather just replace a $20 piston than $100 gears, modify polycarbonate ones are good

I'd just like to point out that this is what I too believed before I learned about AoE and pre-engagement. Don't listen to this advice. You can run a $10 metal rack piston through 50-100K rounds at 410fps@40rps and never break it.

The whole "sacrificial anode" theory of pistons and gears is from an age when extremely nice gears didn't cost $30 and extremely nice pistons didn't cost $10. That age is over.

[ThunderCactus]

Originally Posted by lurkingknight

Polycarb as a material is great for impact resistance... it does not do well with stretching and shearing; it's a bad choice for pistons.

I agree. Polycarbonate is a terrible choice for pistons.

But prometheus pistons aren't polycarbonate, and neither are marui pistons.
Marui I believe are nylon fiber, gives it more elasticity than polycarbonate and therefore way more resistance to cracking.
From what I can tell the prom pistons are polyoxymethylene, from the 2nd tooth removal I've done on a few of them, they cut just like POM. If not they're some kind of high tensile plastic.

Also +1 on a sacrificial piston being an out-dated idea.
If you set up a mechbox properly, the piston will last years. And even if it does strip, it typically won't hurt the gears unless they're really weak.
I've never seen a piston strip or internal failure damage high quality gears

[MaciekA]

There's nothing inherently different about the purple Modify pistons, they are just breaking in setups that don't have carefully adjusted AoE, have pre-engagement or are pushing far too high a rate of fire for a plastic piston. On a related note, you're very rarely going to have an issue with even a simple beige Chinese piston if you are only firing in semi at like 350fps. Reliability is proven at the extremes.

Hence, if you're interested in reliability, the only data that should matter in your research should be coming from people who are testing pistons in setups >400fps >30rps, because people who aren't stressing pistons out significantly are going to have a wild variation of opinions on pistons apropos of nothing in particular, or country-of-origin affinity, hence all these recommendations for magic pistons from the island of Japan

No offense intended to the fine people here, but I assure you that if you put any of those TM, Prometheus and other Japanese pistons into my Diablo without adjusting for AoE or paying attention to any other factors, they should get shredded in seconds. It is all about accounting for those factors. There are very few magical pistons out there.

My personal favourite is also the SHS metal racks like some of the guys above, but the latest batches of these have been super problematic for me. Your mileage may vary since data from various people suggests that bad pistons can hide in otherwise good batches.

You asked about Lonex. I've got a couple Lonex reds in the shop waiting to be tested. I've seen a couple of shredded Lonex blues for example, both in cases where AoE was not correctly adjusted and the strong SHS gears just went right through them. This isn't Lonex's fault. The red "extreme toughness" Lonex pistons are made of some kind of glass-fiber-reinforced nylon. The material feels extremely different from everything else I've held, but I wouldn't expect this to excuse me from adjusting AoE -- not even metal racks do that.

As always, and especially if you're super interested in getting good at rock-solid high performance builds, I'm going to say that it's more important to ensure proper interaction between your sector gear and piston's pickup teeth than to drool over recommendations from us. Verify a mid-range Modify purple running in your system for 5000 rounds at 25rps, then confidently run something much fancier once you've figured out what makes that all tick. Hell, kill a whole bag of shitty anonymous pistons on your way there. You'll learn a ton! (I literally have a big bag of dead pistons if you ever wanna see it..)

TL;DR: You do not need to pay a fortune for good pistons that can handle tremendously stressful setups, and mid-range pistons can survive mid-range stress for long periods of time with some basic adjustments.