FAQ  •  Register  •  Login

Why does my airsoft gun shoot 2 bullets at a time?

Moderators: richardtl, Seventy9

<<

Gladius

Sarge
Sarge

Posts: 42

Joined: 13 Oct 2009, 20:30

Location: Cape Town

Post 31 Jan 2010, 21:03

Why does my airsoft gun shoot 2 bullets at a time?

Hi There,

Was wondering if someone could help me, I have a UTG M14 and have recently service it . A new spring was put in as well as a new hop-up. But during my last game I noticed that it was shooting 2 bullets at one time on a regular basis. Does anyone know what the problem might be?

Regards,
Gladius
Damen AKA Gladius

ICS L85 A2
WE SIG P226
<<

richardtl

User avatar

General
General

Posts: 7850

Joined: 15 May 2008, 23:50

Location: Vereeniging

Post 31 Jan 2010, 21:47

Re: Why does my airsoft gun shoot 2 bullets at a time?

Double firing is normally caused by a couple of things, but since you say it occurred since it was last serviced. I would take it back to whoever serviced it as they changed both the hop-up and opened the mechbox. So in this case it could be either of these and not something like a mag spring on steriods.

IF the hop-up is working properly it may lallow more than one BB through. This is easily checked by engaging more hop-up and seeing if the problem goes away.

Otherwise it is a mechbox problem
If the mechbox sounds like it is rewinding after a shot the antireversal latch may not be engaging properly and this will lead to allsorts of nice side effects like broken pistons. I've had M14 mechboxes do double firing before, as it seems they quite prone to timing issues unlike most other mechboxes. Also as the M14 mechbox has all the latches external to the box if they're not nice and freemoving they could also induce the problem, as they let the mechbox overrun-KART mechboxes and clones (UTG maybe?????) really like this if messed around.

This is easily seen by the feed nozzle doing 2 cycles back and forward per shot, as observed from the mag well.
Image
<<

Francois

User avatar

Captain
Captain

Posts: 647

Joined: 16 Apr 2009, 14:19

Location: Pretoria

Post 08 Sep 2010, 21:37

Re: Why does my airsoft gun shoot 2 bullets at a time?

Oom Richard....how do you know that it is correctly timed? Is it by trial and error or should the gears be alined in a specific way? Because i did try the internet and the forum but there isnt really a direct way of stating where or what angle the gears should be.

I also had like a bright flash idea, could it be the tappet plate it self causing it by pulling too far back and letting in 2 bbs because some tappet plates are differntly shaped at the end where it rolls over the cam on the gear, some are in a straight angle where some are concave shape and some are both. Just by sanding it down abit wil reduce the distance off the nozzle pulling back and just maybe it will solve the problem of the double feed? Its just a thought i got while drinking a beer.
Francois
Image
<<

Francois

User avatar

Captain
Captain

Posts: 647

Joined: 16 Apr 2009, 14:19

Location: Pretoria

Post 08 Sep 2010, 21:39

Re: Why does my airsoft gun shoot 2 bullets at a time?

Oom Richard....how do you know that it is correctly timed? Is it by trial and error or should the gears be alined in a specific way? Because i did try the internet and the forum but there isnt really a direct way of stating where or what angle the gears should be.

I also had like a bright flash idea, could it be the tappet plate it self causing it by pulling too far back and letting in 2 bbs because some tappet plates are differntly shaped at the end where it rolls over the cam on the gear, some are in a straight angle where some are concave shape and some are both. Just by sanding it down abit wil reduce the distance off the nozzle pulling back and just maybe it will solve the problem of the double feed? Its just a thought i got while drinking a beer.
Francois
Image
<<

RogueRunner

User avatar

Colonel
Colonel

Posts: 3853

Joined: 21 Aug 2007, 17:22

Location: Pretoria

Post 08 Sep 2010, 21:47

Re: Why does my airsoft gun shoot 2 bullets at a time?

Could this not be a tappet plate problem?
Guns have a point and click interface

"I am COMPLETELY out of ammo. That's never happened to me before." Burt Gummer

Christo
<<

djbrettv

User avatar

Colonel
Colonel

Posts: 3805

Joined: 14 Apr 2009, 16:09

Location: Durban, KZN

Post 09 Sep 2010, 06:37

Re: Why does my airsoft gun shoot 2 bullets at a time?

I get occasional double feeding with my MP5 but only on semi so im interested to know the solution to this. If its the mag spring then it should only happens with the first few rounds when the pressure is the highest and then it will stop right?
Brett (MEATHOOK)
"Play in a way that allows the opposing players to enjoy themselves too → Everybody has a good time."
<<

richardtl

User avatar

General
General

Posts: 7850

Joined: 15 May 2008, 23:50

Location: Vereeniging

Post 09 Sep 2010, 06:49

Re: Why does my airsoft gun shoot 2 bullets at a time?

Francois wrote:Oom Richard....how do you know that it is correctly timed? Is it by trial and error or should the gears be alined in a specific way? Because i did try the internet and the forum but there isnt really a direct way of stating where or what angle the gears should be.

I also had like a bright flash idea, could it be the tappet plate it self causing it by pulling too far back and letting in 2 bbs because some tappet plates are differntly shaped at the end where it rolls over the cam on the gear, some are in a straight angle where some are concave shape and some are both. Just by sanding it down abit wil reduce the distance off the nozzle pulling back and just maybe it will solve the problem of the double feed? Its just a thought i got while drinking a beer.


Most gearboxes will time themselves correctly. But my M14 had problems with it running a bit back due to a weak reversal latch, eventaully it broke 2 pistons. This caused double/triple feeding.

The distance the nozzle moves back does not really factor.

Other problems could be too much mag spring pressure(normally first couple of rounds). No hop-up, etc.

The biggest problem is normally fiddling on a AEG that was working fine and then someone with no mechanical aptitude totally cocks it up.
Image
<<

Francois

User avatar

Captain
Captain

Posts: 647

Joined: 16 Apr 2009, 14:19

Location: Pretoria

Post 09 Sep 2010, 07:44

Re: Why does my airsoft gun shoot 2 bullets at a time?

Thanks oom. I dont think its my hop thata the problem because it was shooting fine until i replaced my tappet plate and thats when i started to think it could be the tappet plate.

Think i will open it up and rotate the gears and position them to see if there is a difference and if that doesnt worl i will sand the end of the tappet so that it also looks the same shape at the end as my old one. Trial and error time.
Francois
Image
<<

AlexSch

User avatar

General
General

Posts: 5221

Joined: 23 May 2008, 16:31

Location: Pretoria

Post 14 Sep 2010, 18:50

Re: Why does my airsoft gun shoot 2 bullets at a time?

Gooi weg. Koop nuwe een... :P
Image

... ALEX aka Suikerriet...
<<

Francois

User avatar

Captain
Captain

Posts: 647

Joined: 16 Apr 2009, 14:19

Location: Pretoria

Post 14 Sep 2010, 21:41

Re: Why does my airsoft gun shoot 2 bullets at a time?

haha nee mnr alex.... Goeie wat weg?

I did found a couple of websites and forums telling you how to time you gearbox.
Francois
Image
<<

AlexSch

User avatar

General
General

Posts: 5221

Joined: 23 May 2008, 16:31

Location: Pretoria

Post 15 Sep 2010, 08:10

Re: Why does my airsoft gun shoot 2 bullets at a time?

Francois wrote:haha nee mnr alex.... Goeie wat weg?

I did found a couple of websites and forums telling you how to time you gearbox.


you are having to frow away you geforked AEG! :P
Image

... ALEX aka Suikerriet...
<<

richardtl

User avatar

General
General

Posts: 7850

Joined: 15 May 2008, 23:50

Location: Vereeniging

Post 15 Sep 2010, 09:09

Re: Why does my airsoft gun shoot 2 bullets at a time?

Interesting as the only thing you can really alter is when the reversal latch takes, the rest is interconnected by gears and cams and can't be varied, so I would like someone explain that to me.
Image
<<

AlexSch

User avatar

General
General

Posts: 5221

Joined: 23 May 2008, 16:31

Location: Pretoria

Post 15 Sep 2010, 09:40

Re: Why does my airsoft gun shoot 2 bullets at a time?

I never ever checked the timing of the bevel gear and anti reversal latch. I have had problems with double feeding before in a CM028 that I fixed for a friend once. Now it ended up being the hopup rubber itself that was a bit dodge. I opened up the mouth a bit with a hot iron and in the end it shot fine. Just double check everything in the hopup unit again. Pay attention to the rubber itself. Try an old one or something and see if it makes a difference.
Image

... ALEX aka Suikerriet...
<<

Francois

User avatar

Captain
Captain

Posts: 647

Joined: 16 Apr 2009, 14:19

Location: Pretoria

Post 15 Sep 2010, 19:25

Re: Why does my airsoft gun shoot 2 bullets at a time?

OK but before any one starts throwing rocks at me this is what went through my head.....

This is only illustrations and are not to scale.... this is what I found with my research on the web. On my rifle i did replace the hop up bucking with a new guarder bucking, Mad bull Bucking and with my stock bucking and all of them ended up the same, still firing 2 bbs in semi and in full.

I will properly examine my gearbox this weekend.
Attachments
Drawing1_recover-Layout1.jpg
This is in what potion the gears must be in when installing the gears. the sector gears cam must touch the Tappet Plate and the anti reverse latch must engage the bevel gear as well.
Drawing1_recover-Layout1.jpg (46.67 KiB) Viewed 1115 times
Drawing1_recover-Layout1 (2).jpg
If you install the gears without checking the the reverse latch engages the bevel gear your timing could be out. followed by the following image
Drawing1_recover-Layout1 (2).jpg (46.54 KiB) Viewed 1115 times
Drawing1_recover-Layout1 (3).jpg
If your timing is out by 2 teeth this is what the gears position would be after 1 shot has fired.
Drawing1_recover-Layout1 (3).jpg (46.57 KiB) Viewed 1115 times
Francois
Image
<<

richardtl

User avatar

General
General

Posts: 7850

Joined: 15 May 2008, 23:50

Location: Vereeniging

Post 15 Sep 2010, 19:50

Re: Why does my airsoft gun shoot 2 bullets at a time?

You picture is showing half a mech box and not a full mechbox. Parts cannot be looked at in siloation and without the tension of the various springs.

The timing cannot be out ever as everything is gear related, i.e. the gear driving the piston has a certain number of teeth. The tappet plate is spring loaded. The piston is spring loaded. The switch is mechanically cut off by a cam. So everything returns to a reat state. You can assemble everything in whatever "timing" you want and it will return to a rest state.

The only thing you do is assemble the mech box with the tappet plate fully retracted as it makes it easier to get everything together. The only thing you can alter slightly is the reversal latch. Ever wondered why some makes of gears have more latch notches?????
Image
Next

Return to Tech/Upgrades

Who is online

Users browsing this forum: No registered users and 2 guests

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group.
Designed by Vjacheslav Trushkin for Free Forums/DivisionCore.