MP5 SD mechbox parts recommendations

[The Saint]

Originally Posted by coachster

any benefit from using both over?

Even more cushioning? I think that's the idea anyways. At the very least, the o-ring on the MASK piston head is silicon rather than rubber. Apparently that's suppose to be a good thing.

[coach]

Thanks for the input. I do appreciate the help.

Decisions, decisions, decisions. Systema or Sorbo? Oh well, I'll sleep on it and decide when I have the parts in hand.

[llotech]

Originally Posted by coachster

Thanks for the input. I do appreciate the help.

Decisions, decisions, decisions. Systema or Sorbo? Oh well, I'll sleep on it and decide when I have the parts in hand.

Why don't you do both. Cut the Sorbo to fit in the Systema, thats what I did and it works great

Oh, the tooth missing, that is what caused the piston to retract and jam, the sector gear mismeshed since it grabbed the second tooth and the spring compressed fully preventing the gear from releasing the piston. Keep the bearing spring guide, cylinder is stock something, likely TM, no reason to change it or the head.

I am putting a lipo in my mp5 and I was told that this was needed cause of the speed to prevent damage. Now what is true or not.

[coach]

Originally Posted by llotech

Why don't you do both. Cut the Sorbo to fit in the Systema, thats what I did and it works great

I guess I could but I read a review that the systema didn't silence much and also resulted in a decrease in FPS. I'm aiming for 335-350fps.

I am putting a lipo in my mp5 and I was told that this was needed cause of the speed to prevent damage. Now what is true or not.

I see some truth to doing that in your situation with high ROF. Something about allowing the sector gear to mesh properly. What spring are you using?

I have the Modify High Torque Modular gearset already. I'm not planning to go high speed for high ROF so using a lipo is not necessary.

[llotech]

Originally Posted by coachster

I guess I could but I read a review that the systema didn't silence much and also resulted in a decrease in FPS. I'm aiming for 335-350fps.




I see some truth to doing that in your situation with high ROF. Something about allowing the sector gear to mesh properly. What spring are you using?

I have the Modify High Torque Modular gearset already. I'm not planning to go high speed for high ROF so using a lipo is not necessary.

The Sorbo helps with the sound too and I figure they work better together than apart.

I have a 100 spring in now and before the lipo batt I was getting ~330 fps so with the high ROF I think it will be more fps but I don't know how much yet.

[coach]

Originally Posted by llotech

The Sorbo helps with the sound too and I figure they work better together than apart.

I have a 100 spring in now and before the lipo batt I was getting ~330 fps so with the high ROF I think it will be more fps but I don't know how much yet.

Negatory on ROF affecting FPS

[coach]

Picked up parts from Jugglez today.

Modify Cylinder set
Modify S100 (the one in there was shorter than the S90 spring)
Sorbo piston head and pad

Will see how it all goes together.

[coach]

Update:

Installed everything and it's shooting well but seems underpowered. The spring was a significant upgrade so I don't see how it can't pierce the side of a coke can. Yeah, that's right, it won't penetrate even one side.

Could it be the Mask sorbo piston head in combination with the sorbo pad? How can I go about testing for leaks? There is still a fair amount of air coming out of the barrel. All the orings were oiled and appear to have a decent seal. I used a thin coat of 20wt shock oil on everything.

I was expecting the Modify S100 to be slightly overpowered in the end.

[Donster]

cost more, but you can never go wrong with Prometheus parts. They are the unnecessarily more pricy version of Modify.

[coach]

Originally Posted by DONSTER 125

cost more, but you can never go wrong with Prometheus parts. They are the unnecessarily more pricy version of Modify.

doesn't help me all that much but thanks for the info.

[Nova316]

Have u checked your air seal? When your mechbox is open push the piston into the cylinder with your finger over the end of the cylinder head without the airnozzle. If you can push it down and theres resistance your airseal is good. If not you may need to check your piston Oring or your cylinder had Oring. Then put on the airnozzle and try it again, if air leaks out crazily you may also need a new air nozzle, I believe Modify has a double Oring one which is great.

[coach]

yes, I did a basic compression test but didn't test to see if there was a leak between the cylinder head and nozzle. there was significant resistance when I tried to push the piston into the cylinder while covering the cylinder head opening. I guess I'll have to tear it down again and make sure there is a proper seal between the cylinder head and nozzle. will probably give all the orings another silly bath to swell them up a bit. I also did try to stretch out the one on the MASK piston head but it didn't stretch much. more than likely because it is silicone.

the nozzle that comes with the cylinder set is a POM nozzle and not the modify one so no oring.

[CDN_Stalker]

You have a big airleak somewhere, don't always blame the spring, that 100 will blast through both sides of a can easily. Leak can be anywhere between the pistonhead O-ring to the hop up rubber. If you got a ported piston head, then I've had problems with those also not inflating properly every time and causing wildly varying fps readings, even over 100fps difference at times. Someone once mentioned to not use grease on the O-Ring, just use a wipe of silicon oil, I tried it and it worked great right away............... haven't tried recently though. But make sure your hop up rubber is good too, it'll affect the velocity. Avoid the blue rubber Madbull ones, I have yet to find a set that actually seals well without being distorted, and I actualy bought at leasta dozen sets of them last year to use in client's guns. Not worth the price paid at all, even if cheap.

[coach]

Long over due update:

With talking about testing the MadBull .25 tracers at next weekends FR game, I finally decided to break the gun down and open the mechbox once again. I'm getting good at this!

Anyway, I think I discovered the leak or possible leaks. It is possible that the hopup rubber was not seated quite right. While checking the madbull TB length with my tracer unit sensor the inner barrel seemed to seat better and actually lock down with the retaining c-clip. (MB TB = 229mm but is about 15-20mm longer than the stock UTG inner) TB clears the tracer sensor so good on that front. Rubber is the stock CA one that comes with the newer metal unit. Will continue to use it since it's brand new.

Next possible leak is with the nozzle. I took the cylinder out and did another compression test and all was good. Pushing the piston in and pulling it out while covering the nozzle tip with my finger results in little to no movement of the piston. But I noticed when the nozzle is near the end of the cylinder head, just before the spring releases, I can hear air leaking between the cylinder head and nozzle.

Now is there any way in ensuring a better seal between them? Will teflon tape work and stay put? Would it not eventually get worn and moved by the moving nozzle?

I will probably just end up getting the modify one with the double orings to eliminate this air leak. More money in to this gun and I will eventually need to get a new lower receiver. Cracks are forming from slight fitment issues and JB Weld can only do so much. :P

Last question, is the tappet plate suppose to flex much during a cycle? mine seems to bend a whole lot when I try to advance the piston by turning the gears.

[coach]

Okay, so I gave in and figured I'd just get a new Modify tappet and Modify nozzle (w/oring)

Hope this eliminates the air leak otherwise I'm lost as to what else it could be.