low fps issue

[Haru]

Just had a game this morning and I chronoed at 250fps on .25bbs which seemed a little low I was expecting to get around 280fps with an m95 spring

The whole gun is stock apart from a perun and spring installed, reshim and regrease. Air seal seemed fine last time I opened the gearbox.

I did leave my gun precocked for 3 days but no way a brand new spring would lose that much strength after 3 days.

I may consider just going back to the stock spring which shot a tiny bit hot.

 

Also any reason why a would 2600 mah 11.1v lipo run out in under 500 shots? had to play the rest of the day with 7.4v 

 

[Pseudotectonic]

What gun?

 

You mean you chrono'd 280 before, sat 3 days precocked, and now chronos 250?

 

And the battery shouldn't run out so fast, either it is bad or the motor is too low torque, but since it is stock with a weak spring it shouldn't, so it could be the shimming, or the grease

[Adolf Hamster]

Can't say it isnt the spring, plenty of debate one way or the other if modern steels care about being left under load but whichever side you come down on creep is a material phenominon that is known to exist and the question is not if but how much it'll relax by.

 

What's the situation for thrust bearings in the box? If you've got one on each end of the spring then ditching the piston end can be a handy way to drop a few fps to get the original under.

 

As for the battery, assuming it's not ancient then theres a load of possibilites from just not fully charged to a cell imbalance, it has been known for some chargers (particularly the 3-led type) to partially die leaving one cell uncharged.

[Haru]

53 minutes ago, Pseudotectonic said:

What gun?

 

You mean you chrono'd 280 before, sat 3 days precocked, and now chronos 250?

 

And the battery shouldn't run out so fast, either it is bad or the motor is too low torque, but since it is stock with a weak spring it shouldn't, so it could be the shimming, or the grease

its a cyma plat mp5, and i meant with an m95 spring theoretically i was expecting to get around 270-280fps with .25 i had it precocked a few days before my game when i was test firing it. I don't think it is shimming or grease but I won't rule it out as it was the first gun I've had to open up, but the gun sounds great I dont hear much gear grinding or motor whirring.

Edited September 3, 2023 by Haru

[Pseudotectonic]

The shorter barrel might have something to do with it

[Haru]

23 minutes ago, Adolf Hamster said:

Can't say it isnt the spring, plenty of debate one way or the other if modern steels care about being left under load but whichever side you come down on creep is a material phenominon that is known to exist and the question is not if but how much it'll relax by.

 

What's the situation for thrust bearings in the box? If you've got one on each end of the spring then ditching the piston end can be a handy way to drop a few fps to get the original under.

 

As for the battery, assuming it's not ancient then theres a load of possibilites from just not fully charged to a cell imbalance, it has been known for some chargers (particularly the 3-led type) to partially die leaving one cell uncharged.

i didnt recall seeing any bearings around the spring or piston, maybe ill have a look around when im bothered to open the gearbox again, also it is a brand new battery from componentshop and I use those shitty 3-led type chargers been meaning to buy a better charger but it does the job in a pinch.

4 minutes ago, Pseudotectonic said:

The shorter barrel might have something to do with it

i shouldnt be losing 30-40 fps from the barrel length though should I. I am hoping it is just the spring and next week I'll see what happens at chrono otherwise I may suspect there is an air leak somewhere.

[Adolf Hamster]

53 minutes ago, Haru said:

didnt recall seeing any bearings around the spring or piston, maybe ill have a look around when im bothered to open the gearbox again,

 

Might not be, some guns dont have them or have a couple of washers on the spring guide that theoretically can spin. Generally i like a proper bearing on the spring guide and nothing on the piston.

 

55 minutes ago, Haru said:

use those shitty 3-led type chargers been meaning to buy a better charger but it does the job in a pinch.

 

Might want to pay real close attention to it if you're using it again. The visual cue is on a 3 cell battery one of the lights won't change when charging (ie the same effect you get when plugging in a 2 cell battery), assuming it's the same type as i've seen.

 

A better charger is one thing but a really useful bit of kit is a cell checker, even for as simple as "did i remember to charge this battery" but also can tell you outright if for example the charger has failed to charge one cell.

[ak2m4]

What brand is the M95 ?

[Haru]

10 minutes ago, ak2m4 said:

What brand is the M95 ?

asg

[ak2m4]

Ah sorry I don't really know much about them, if it was one of mine I could have helped, sent out a replacement to try etc.  My M95's on 0.25 hit around 280fps with a 260mm.  These types of issues are tricky to diagnose without a "benchmark" spring.  If you truly think it's the spring you should measure the length and the wire thickness and talk to the place you purchased it from, they can compare it to another spring.

 

Ah just had a thought!  I think CYMA platimum short stroke their builds, you should check this first.

[MrTea]

7 hours ago, Haru said:

Also any reason why a would 2600 mah 11.1v lipo run out in under 500 shots? had to play the rest of the day with 7.4v

For reference; my custom Mk18, when playing outdoors, will last about 3-4 hours on a 1500mah 11.1v LiPo with a mix of semi and full auto fire. Usually run through about 10-12 150 round mid-caps. It's an Amazon special to boot to fit my stock tube.

When playing indoors with it, it'll last all night in semi-auto without the LiPo alarm from the MOSFET coming on.

I think there's something wrong with the battery. No way should it die that quick.

[Haru]

9 minutes ago, MrTea said:

For reference; my custom Mk18, when playing outdoors, will last about 3-4 hours on a 1500mah 11.1v LiPo with a mix of semi and full auto fire. Usually run through about 10-12 150 round mid-caps. It's an Amazon special to boot to fit my stock tube.

When playing indoors with it, it'll last all night in semi-auto without the LiPo alarm from the MOSFET coming on.

I think there's something wrong with the battery. No way should it die that quick.

ive actually plugged the battery back in the gun when i got home and it was working fine, which was odd because I was getting the lipo alarm and no response from the trigger during the game

37 minutes ago, ak2m4 said:

Ah sorry I don't really know much about them, if it was one of mine I could have helped, sent out a replacement to try etc.  My M95's on 0.25 hit around 280fps with a 260mm.  These types of issues are tricky to diagnose without a "benchmark" spring.  If you truly think it's the spring you should measure the length and the wire thickness and talk to the place you purchased it from, they can compare it to another spring.

 

Ah just had a thought!  I think CYMA platimum short stroke their builds, you should check this first.

they do come with 13:1 gears stock, idk if that matters. im not too keen on teching

[Colin Allen]

55 minutes ago, ak2m4 said:

Ah just had a thought!  I think CYMA platimum short stroke their builds, you should check this first.

They do, which will have a significant impact on the power delivered at the nozzle.

[ak2m4]

23 minutes ago, Colin Allen said:

They do, which will have a significant impact on the power delivered at the nozzle.

Ah Ha, we have a winner 🙂

 

[Haru]

guess ill have to switch springs then

[SSPKali]

20 hours ago, Haru said:

guess ill have to switch springs then

Also switch out the Cyma nozzle as they are usually leaky as hell 😂 AK2M4 should have a suitable o-ring nozzle (measure up the length with calipers to be sure!) and replace while the gearbox is open.