Trials of a CYMA P90 in the hands of a noob
 

Although pistols are my CQB weapon of choice, I picked up a CYMA P90 to replace my CYMA MP5 as "backup" or when I want to be cover fire.

I've taken apart, reassembled and upgraded half a dozen pistols so I'm not a noob, but not an expert by any means. For AEGs, I have half a dozen as well but never taken them fully apart. I do like to tinker with mechanical watches (ETA, Miyota, cheapie 23/21J) so I have no fear and balls of steel for this sort of task. Of course, a healthy play budget helps!

The CYMA P90 (CM.060) is a pretty solid gun and was around $190 from Depot. I was holding out for a KA variant but none hit my magical $275 asking (yet) and the price gap was huge for the CYMA so I jumped on it. Plus, I've had good times with the CYMA MP5 so I'm ok with the brand from a casual play perspective.

Fast forward. With the basics sorted out like sling, optic, etc I was ready to hit the field until I thought to chrono it first. At stock setting with hop at 50% setting (not tuned yet) it did just under 10 RPS and 390 FPS. Ok, too hot for CQB so I ordered a few items from Airsoft Store Canada...

Reading online, the CYMA P90 should be using an M120 spring which makes sense when you calculate roughly against the FPS. I ordered a Lonex M100SP non-linear spring. To go with it, I got a Lonex V6/7 bearing spring guide (I'm told this may be incorrect?).

Since I'm going to be disassembling, I got an SHS piston o-ring to install as well. Was supposed to order a Sorbopad to fix the AOE but missed it in the order.

On the "might as well" list, I grabbed the Lonex 50D Bucking & Sleeve as it's a simple change. Technically this was supposed to run around 330 FPS so I upgraded (most would say downgraded?) to a Lonex 6.03mm tight bore 247mm.

So on to the build. The bucking and barrel were very easy, but seeing the very cheap feeling hop up unit makes me want to replace that soon.

Removing the gearbox was easy too on the P90 and I've done it before to mildly mod the trigger bar. OPENING the gearbox... I watched a few quick videos and got the gist of it but when it was my turn, it essentially exploded it's parts everywhere. THAT, was fun!

Watching a bunch more videos and fruitlessly trying to find a CYMA exploded gearbox diagram, I started to reassemble -- only to spend 10 minutes trying to locate the clear nozzle. Got the o-ring in, swapped the spring and spring guide. Reassembling was a nightmare as I had a hard time keeping the cylinder, tappet, drive gear and reversal latch in place. In all the videos I've watched, the reversal latch sat nicely with the drive gear -- gingerly but nice. In this case, there was no way I could do it alone so with 4 hands, a forehead, a clamp and tweezers, I/we managed to reassemble the gearbox after 5 tries.

Success right? Other than not being sure where one shim came from (best guessed replaced), everything was generally ok. So I dial the hop up to 50% as a generic reference and chrony the sucker. Didn't catch the RPS yet but it now shoots 405 FPS (!!).

My takeaway from this is -- damn, that KA quick change spring is looking mighty fine now, but can anyone zero in on the oddity of why it's shooting hotter? With the hop up dialled right up, it shoots 395. I'm going to swap back in the stock brass barrel and chrony again but it still doesn't make sense. Occams razor would suggest the Lonex M100 spring > stock CYMA M120 spring -- no other mis-installed parts withstanding.

Thoughts? Yeah, it's long so thanks for reading!



P.S. props to both Huang @ Depot and John @ Airsoft Store Canada for being easy to work with.

>My takeaway from this is -- damn, that KA quick change spring is looking mighty fine now, but can anyone zero in on the oddity of why it's shooting hotter? With the hop up dialled right up, it shoots 395. I'm going to swap back in the stock brass barrel and chrony again but it still doesn't make sense. Occams razor would suggest the Lonex M100 spring > stock CYMA M120 spring -- no other mis-installed parts withstanding.

Obviously the Lonex spring doesn't use the same rating system as other springs, or can't be compared apples to apples.

That's my thinking and really the only thing that makes sense. I did read before about the M vs SP marking on springs but I trusted the M100SP is a M100 as per this post:

Of course, I dropped "two rankings" from M120 to M100 just to be safe but evidently that's not enough for Lonex... ?

Unsure Cyma spring guides but if it doesn't have any bearings the Lonex spring guide is going to increase your FPS and allow for additional compression of the spring.

If the spring guide fits securely inside the tabs of the mechbox then it is the correct spring guide. You should know immediately if it flies out or you can't close the mechbox that it is the wrong type.

If the piston head has any washers or bearings secured inside the piston, you can safely remove it and it will drop your FPS.

What is your target FPS?

The piston head doesn't appear to have any washers or bearings inside. The piston head does have a soft pad and the piston itself has a very, very thin plastic shim.

The original spring guide is metal appears to be ball bearing.

http://images.tapatalk-cdn.com/15/10...24662f3f30.jpg

My target FPS is between 320-350, erring higher if accuracy permits. Then again this is just CQB, I have a TM G36C for outdoors.

The lonex barrel is pure and utter garbage. I've seen better finishes on walmart shotguns.
I'd recommend the madbull stainless or prometheus 6.03
Most M90 and M100 springs are in the 300-350fps range. For cqb your best bet is the M90, because the extra 30-40fps REALLY isn't going to matter very much.

Trials of a CYMA P90 in the hands of a noob
 

Yes TC, I've read both good and bad about the Lonex barrels. Mostly bad. However, a lot of those were older posts and I was betting they're are at least ok now. More so, the supposed testimony their bucking fits awesome on their crappy barrels... Plus, I was ordering some other items from John :) I have no delusions the Lonex barrel is great or good by any means -- just that it's on par with OEM CYMA in this case.

About FPS, I would do M90 but I didn't have a choice at the time I believe. I welcome the higher ROF going M120 to M90.

So I have report to make.

I swapped back in the OEM CYMA brass barrel and set the hop to 50% as a test. It now shoots 375 FPS. What I HAVEN'T tested is the OEM barrel with OEM bucking. I mean, it could simply be a poor bucking/barrel seal that's bringing it down in conjunction with the larger diameter. Hmmm... I should do one more test.

So, with the OEM barrel, OEM bucking and the OEM brass collar, it shoots 400 FPS. Hahaha...

Am I on track about the leak using the Lonex bucking with the OEM barrel, or is the bucking that effective it chopped roughly 25 FPS when only dialled at 50%? I'm guessing the former but hey, entertain any comments :)

I'll test for nozzle sealing later to rule out a bad install.

For an easy and simple solution to fix the high fps problem, since you have a spring for field play, start chopping coils bit by bit of one of the springs until you have your target velocity.

P90 porn for awesomeness

I'll eventually just go and buy another spring since I'll have to open the gearbox once if I get everything right the first shot. Cutting will mean repeatedly opening the gearbox. Then I also have to grind and reseat.

If I do that I might as well short stroke?

So I cut the stock spring. Now it shoots 260 FPS :) Good enough for me until I get the sorbo and a proper M90 spring. With two people, I can now reassemble the gearbox in under 5 minutes -- without having crap fly all over the place and needing to use other appendages. If I really like the P90, I'll jump on a TM P90 HC.

Mine is a g&g base with a few upgrades. Using a Vfc 6.03 extended inner, stock spring, promy bridge nub, modify grey bucking, silver wiring, deans connectors, 7.4 lipo, and shooting about 305 fps. I have a set of 13:1 gears waiting to go in, and waiting on a lonex Titan motor