FPS not what expected!

[Mindcrime13]

hello

i just build the gearbox of a JG Mp5 , i put the following upgrades:

Guarder sp120 spring
Guarder aluminum ball bearing piston Head
Hurricane cylinder head
guarder air seal nozzle
G&P polycarbon Piston
Ball bearing spring guide
7mm steel bushings

for battery: 7.4 25c 1800 lipo

i still do not have the tightbore and bucking in, but with those upgrades i listed above, i still cannot penetrate the bottom part of a coke can, it dents it really good even breaks a bit, but does not goes trough, im using a coke zero can if that matters, it does goes cleanly side to side

is this normal for those upgrades?, or should it anyway break thru the bottom of the can without the tightbore and bucking, ??

[Mitchell12]

You don't really want to penetrate the bottom, That's like 420-450 roughly. WAY to hot for most fields. Both sides of the can is approx 350-370. Lots of room for error though.

[Mindcrime13]

i play in open ares, the closet we shoot each other is like 20 feet hehe, and all the guns here are like 400+!

[Mitchell12]

Originally Posted by Mindcrime13

i play in open ares, the closet we shoot each other is like 20 feet hehe, and all the guns here are like 400+!

There's no need, You'll just shred your internals quicker, Your FPS is excellent for outside. Concentrate on a good tight bore and hop-up rubber.

[Mindcrime13]

so with those upgrade is normal not to go through the bottom of a can?

[cerealmaniac]

Originally Posted by Mitchell12

You don't really want to penetrate the bottom, That's like 420-450 roughly. WAY to hot for most fields. Both sides of the can is approx 350-370. Lots of room for error though.

agreed. my guns shoots through both sides too and it's not where close to 350-370. still very gameble though..

[Mitchell12]

It's not really abnormal. The tight bore will raise you another 10 or so fps you might be able to punch the can through the bottom then. Even so your shooting hot enough, Any harder and your bb's will veer more.

[Styrak]

Originally Posted by Mitchell12

You don't really want to penetrate the bottom, That's like 420-450 roughly. WAY to hot for most fields. Both sides of the can is approx 350-370. Lots of room for error though.

Incorrect. You can go through the bottom of a can with as little as 370-380fps.
Can chronies are useless, you need to use a real chrony.

As for that setup, yes a Guarder M120 should be getting at least 400fps. You must have a bad airseal, or some other problem.

[Mindcrime13]

could a bad bucking do this? the bucking I have is the stock JG, and when I was put it in it rip on the end lip at the end of the barrel

[Mindcrime13]

is it ok to try this:

http://forums.airsoftmechanics.com/i...ic=2151.0;wap2

Deep breath..... OK here is how it works. First pull your mechbox. Set it on semi. Push your finger against the air nozzle (push the nozzle all the way back and hold it there) and pull the trigger. If the piston hangs part way down the cylinder you have great compression. If it returns very slowly you have good compression. If it slams into the cylinder head you have a major air leak.

[AngelusNex]

Yes a torn rubber will drasically drop your fps.

[Styrak]

Originally Posted by AngelusNex

Yes a torn rubber will drasically drop your fps.

+1. That's your problem. Why didn't you mention that before?

[Mitchell12]

Originally Posted by Styrak

Incorrect. You can go through the bottom of a can with as little as 370-380fps.
Can chronies are useless, you need to use a real chrony.

As for that setup, yes a Guarder M120 should be getting at least 400fps. You must have a bad airseal, or some other problem.

Hey I'm just going off what he asked and what's publicly available.

[Mindcrime13]

i dint know that the hop could really cause that! since it was the lip at the end and not the part of the nub

[ujiro]

Any tear in the hop up rubber can and most likely will cause poor air seal between the hop up unit and the barrel.