Airsoft Canada
MILSIG

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

King Arms M4A1 Loss of Pressure/FPS

:

Doctor's Corner

Reply
 
Thread Tools
Old April 14th, 2015, 00:54   #1
AnthonyG
LUser Title
 
AnthonyG's Avatar
 
Join Date: Aug 2014
Location: Pickering/Toronto
King Arms M4A1 Loss of Pressure/FPS

I was having issues loosing pressure such that my gun, which should be shooting ~340fps, was shooting ~210fps.

With some help I isolated the problem to the metal ring that sits over the inner barrel creating a seal with the hop-up unit. First, does this little metal ring have a name? Second, at the moment my fix is that I've put some tape to stop this little metal ring from sliding out. I'd like a more permanent fix and just wondering what I should do?


Edit: I couldn't find an exact image, but basically it's the brass-coloured ring that slides in/under where I've drawn the arrow:

Last edited by AnthonyG; April 14th, 2015 at 00:57..
AnthonyG is offline   Reply With Quote
Old April 14th, 2015, 01:29   #2
L473ncy
 
L473ncy's Avatar
 
Join Date: Oct 2004
Location: 11-30-24-1W5
I've heard of it referred to as a "hop up barrel spacer" before. It should also just be "friction fit" into the hop up unit. It's odd though, is everything stock on it?
__________________
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE
L473ncy is offline   Reply With Quote
Old April 14th, 2015, 02:20   #3
Red Dot
Google level: BOSS
 
Red Dot's Avatar
 
Join Date: Dec 2013
Location: Stouffville, Ontario
Some units use a spring to maintain pressure on that ring. You could try some Teflon tape to seal and secure the part.

Red Dot is offline   Reply With Quote
Old April 14th, 2015, 02:59   #4
RainyEyes
- Professional Complainer who wants to do nothing to help out. QQer maximus, will QQ for Free. Snowflake exemplified.
 
RainyEyes's Avatar
 
Join Date: Sep 2013
Location: Scarbororororough
Are you sure it's not the hop-up rubber pressing down too much that causes fps loss? I've had that happen on one of my guns previously.
RainyEyes is offline   Reply With Quote
Old April 14th, 2015, 04:15   #5
Zfurlong
 
Join Date: Sep 2014
Location: Oromocto
Use Teflon tape to wrap the end of the hop rubber, that should solve your issue. I started doing it to all my guns and have never had an issue once I started doing that (providing of course that any issue I did have was compression loss caused by the rubber)
__________________
current armament:
mk43, ump.45, p90, barret, m14, g33, k98, m4 tac, m4 swat, mp5 navy, vsr10, p226, m9.
Zfurlong is offline   Reply With Quote
Old April 14th, 2015, 11:26   #6
AnthonyG
LUser Title
 
AnthonyG's Avatar
 
Join Date: Aug 2014
Location: Pickering/Toronto
Quote:
Originally Posted by L473ncy View Post
I've heard of it referred to as a "hop up barrel spacer" before. It should also just be "friction fit" into the hop up unit. It's odd though, is everything stock on it?
Stock.

Quote:
Originally Posted by RainyEyes View Post
Are you sure it's not the hop-up rubber pressing down too much that causes fps loss? I've had that happen on one of my guns previously.
I crono'd it before an after. It's definitely the spacer. I was at a field, so the employee crono'ing my gun suggested the same thing, and it didn't affect it.
AnthonyG is offline   Reply With Quote
Old April 14th, 2015, 11:36   #7
AnthonyG
LUser Title
 
AnthonyG's Avatar
 
Join Date: Aug 2014
Location: Pickering/Toronto
Quote:
Originally Posted by Zfurlong View Post
Use Teflon tape to wrap the end of the hop rubber, that should solve your issue. I started doing it to all my guns and have never had an issue once I started doing that (providing of course that any issue I did have was compression loss caused by the rubber)
Are you saying, you wrap this part in teflon tape?




Or the part inside the hop up unit I labelled B?:


Last edited by AnthonyG; April 14th, 2015 at 11:43..
AnthonyG is offline   Reply With Quote
Old April 14th, 2015, 13:05   #8
RainyEyes
- Professional Complainer who wants to do nothing to help out. QQer maximus, will QQ for Free. Snowflake exemplified.
 
RainyEyes's Avatar
 
Join Date: Sep 2013
Location: Scarbororororough
The END of the hopup rubber. So the place where the ring would sit on the hop-up where you labeled "where i put tape".

The goal is to prevent compression loss. So you would wrap the end part to help seal it, not inside.
RainyEyes is offline   Reply With Quote
Old April 14th, 2015, 13:17   #9
Wrath144
formerly steyr
 
Join Date: Sep 2005
Location: Winnipeg, Manitoba
Use an oring.
__________________
BROFORCE
Admin - Winnipeg Airsoft
Wrath144 is online now   Reply With Quote
Old April 14th, 2015, 17:44   #10
AnthonyG
LUser Title
 
AnthonyG's Avatar
 
Join Date: Aug 2014
Location: Pickering/Toronto
Quote:
Originally Posted by RainyEyes View Post
The END of the hopup rubber. So the place where the ring would sit on the hop-up where you labeled "where i put tape".

The goal is to prevent compression loss. So you would wrap the end part to help seal it, not inside.
Got it, So I've got it wrapped in the right place as it stands. I guess teflon tape is better than the electrical tape that I have on there now.
AnthonyG is offline   Reply With Quote
Old April 15th, 2015, 18:07   #11
Zfurlong
 
Join Date: Sep 2014
Location: Oromocto
Under that brass ring, over the end of the hop rubber. It should tighten up that brass ring to the inner and allow it to sit where it should, and it should help the airseal
__________________
current armament:
mk43, ump.45, p90, barret, m14, g33, k98, m4 tac, m4 swat, mp5 navy, vsr10, p226, m9.
Zfurlong is offline   Reply With Quote
Old April 15th, 2015, 18:30   #12
Stealth
Mr. Silencer
 
Join Date: Dec 2001
Location: Toronto
If you have floss around, you need to do this mod:
https://www.youtube.com/watch?v=QInMxQPKyb8

This ensures a proper seal at the interface between your hop up unit and your hop up sleeve.

Since you mentioned KA, it doesn't really apply, but another source of air leaks is at the interface between your nozzle and hop up sleeve. M16 hop up units have a tiny spring which pushes the hop up unit backwards. This spring is weak and if tolerances are loose, the hop up unit can move forwards during shooting, thereby losing the proper seal. These o-rings keep things tight and maintain the proper seal.
Stealth 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
MILSIG

All times are GMT -4. The time now is 16:27.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.