Airsoft Canada
http://triggerairsoft.com/shop/

Go Back   Airsoft Canada > Discussion > Doctor's Corner
Home Forums Register Gallery FAQ Calendar
Retailers Community News/Info International Retailers IRC Today's Posts

TM MP5 - Low velocity - FIXED

:

Doctor's Corner

Reply
 
Thread Tools
Old August 1st, 2006, 01:53   #1
Avenging Angel
 
Join Date: Feb 2004
Location: Calgary, AB
TM MP5 - Low velocity - FIXED

Hey guys, I need some help with a problem I'm having but first, here's the stats of the gun.

TM MP5A4 HG
M120 Spring
Metal bushings
Poly Carb Piston
Poly Carb Piston head
Metal Spring Guide

The problem I'm having is that the gun is only shooting at 150fps with the current modifications. Before the upgrades were installed, the gun was shooting 285fps on average.

I can't figure out what the problem might be. I've replaced the O-ring on the piston head, I've tried 2 other springs (an M120 and a stock one) with the same effect of 150fps. The nozzle is also fine.

I guess what I'm asking is, what's the next step? What else do I need to try to get this thing working again?
Avenging Angel is offline   Reply With Quote
Old August 1st, 2006, 02:03   #2
brently0725
 
brently0725's Avatar
 
Join Date: Apr 2006
Location: Mission, BC
Did you change the piston head seal at all?
Also the cylinder might be to big for your new piston (had it happen with a hurricane kit I bought)
Did you check to see if your hop up rubber is not folded or creased.

I love fixing my own stuff like most but sometimes after trying for a while you might want to seek the help of a proffesional before doing something you regret and make a $500 paperweight.

LOL GOOD LUCK MAN!!
__________________
-TM AK Beta Spetz -TM MP5 SD5 -TSD VSR10 -Ares G39C -A&K Tan Magpul Masad -We Tech M9 Tac Masterling -1Tornado Impacts
V2/3 Gun Doc and BA experience
brently0725 is offline   Reply With Quote
Old August 1st, 2006, 02:08   #3
mcguyver
 
mcguyver's Avatar
 
Join Date: Aug 2005
Location: Northern Alberta
Is the cylinder in the correct way, with the port towards the rear of the mechbox?
__________________
Age verifier Northern Alberta

Democracy is two wolves and a sheep discussing what's for dinner.

Freedom is the wolves limping away while the sheep reloads.

Never confuse freedom with democracy.
mcguyver is offline   Reply With Quote
Old August 1st, 2006, 02:13   #4
Avenging Angel
 
Join Date: Feb 2004
Location: Calgary, AB
Hop-Up is in working condition and the O-Ring on the piston head is making what appears to be a good seal with the cylinder walls.

I'm fairly familiar with the internals of the MP5 series as I have owned 5 of them through out my career. Also, just for information more than anything, I have taken it to a gun doctor and he has no idea what's going on either. Everything "appears" to be fine.
Avenging Angel is offline   Reply With Quote
Old August 1st, 2006, 02:17   #5
Avenging Angel
 
Join Date: Feb 2004
Location: Calgary, AB
Quote:
Originally Posted by mcguyver
Is the cylinder in the correct way, with the port towards the rear of the mechbox?
I'll have to check on this... I do believe that the port is currently near the front of the box. I recieved it back that way after I sent the gun out to have the upgrades done.
Avenging Angel is offline   Reply With Quote
Old August 1st, 2006, 02:20   #6
mcguyver
 
mcguyver's Avatar
 
Join Date: Aug 2005
Location: Northern Alberta
If it's to the front then it's wrong. You lose about 2/3 of your available cylinder volume and alot of FPS as well.
__________________
Age verifier Northern Alberta

Democracy is two wolves and a sheep discussing what's for dinner.

Freedom is the wolves limping away while the sheep reloads.

Never confuse freedom with democracy.
mcguyver is offline   Reply With Quote
Old August 1st, 2006, 02:36   #7
Prowler
 
Prowler's Avatar
 
Join Date: Feb 2004
Location: Surrey, BC
Send a message via ICQ to Prowler Send a message via AIM to Prowler
What I do is I take the cylinder, piston, air nozzle system out. Then I take my finger and plug the airnozzle so no air can escape. If you push the piston forward and there is no air escaping then its a good seal. You can use this method to determine if your piston is pushing enough air. Try different levels of force to the piston too.

If your getting low fps i would also look at the air seal in the hopup. Otherwise it might be the spring. *shrug* Can't really tell without looking at it myself.

Hope that helps
__________________
Prowler is offline   Reply With Quote
Old August 1st, 2006, 02:54   #8
Avenging Angel
 
Join Date: Feb 2004
Location: Calgary, AB
Quote:
Originally Posted by mcguyver
If it's to the front then it's wrong. You lose about 2/3 of your available cylinder volume and alot of FPS as well.
Thanks man! That was the problem! The gun is now shooting a healthy 375.
Avenging Angel is offline   Reply With Quote
Old August 1st, 2006, 02:55   #9
Avenging Angel
 
Join Date: Feb 2004
Location: Calgary, AB
Quote:
Originally Posted by Prowler
What I do is I take the cylinder, piston, air nozzle system out. Then I take my finger and plug the airnozzle so no air can escape. If you push the piston forward and there is no air escaping then its a good seal. You can use this method to determine if your piston is pushing enough air. Try different levels of force to the piston too.

If your getting low fps i would also look at the air seal in the hopup. Otherwise it might be the spring. *shrug* Can't really tell without looking at it myself.

Hope that helps
Thanks for that bit of information as well! I'll store that away in my brain for later reference.
Avenging Angel is offline   Reply With Quote
ReplyTop


Go Back   Airsoft Canada > Discussion > Doctor's Corner

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Airsoft Canada
http://triggerairsoft.com/shop/

All times are GMT -4. The time now is 08:32.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.