M4A1 shooting 2-3 bb's per shot?

LIL GING · November 10th, 2011, 19:52

so i have a classic army m4a1 RIS system and it took a rough fall when i got flipped off a atv playing, and now it shoots 2-3 bb's everytime i pull the trigger. what could be the posible problem? could it be the hop up letting to meny in or a bigger problem and how could i fix this and get my gun back to normal?

krap101 · November 10th, 2011, 19:59

I would say the problem is between the air nozzle and the bucking. My guess would be that the air nozzle isn't correctly seated within the tappet plate.

LIL GING · November 10th, 2011, 20:29

so how would i go about fixing that?

krap101 · November 10th, 2011, 21:00

Are you able to disassemble gearbox or find someone who can?

LIL GING · November 10th, 2011, 22:30

yeah i know how to

CDN_Stalker · November 10th, 2011, 23:03

100% hop up issue, check that and don't bother with the mechbox, isn't the problem. Check the barrel seating in the hop up unit, and the rubber condition/setting. This is exactly what happens when the C shaped clip that holds the inner barrel and hop up rubber into the hop up unit cracks, its grip is lessened and when shooting the inner barrel moves forward a bit, allowing 2-3 BBs to load at a time.

LIL GING · November 10th, 2011, 23:18

well i know when i shot it with out the interbarrel attached the nozzle pulls back into the gear box a bit could that be it?

CDN_Stalker · November 10th, 2011, 23:23

No, that's normal operation, the nozzle never rests at the full forward position after every shot. It's a hop up issue, trust me, I've fixed at least a dozen of these over the years, always the same problem, hop up.

See, the way the system allowsonly one BB to be loaded and shot every time is the hop up nub, the thing that puts the back spin on the BB. It sticks into the barrel, the nozzle pulls back and one BB is let into the chamber and sticks there, the nozzle pushes forward, the next BB in line gets pressed down into the magazine, the nozzle sits full forward and the piston is released, pushing the BB out of the barrel. If the one BB amount of space between the BB feed and the hop up nub is increased to the space that will allow 2-3 BBs to enter, then they will. And the only thing that can allow that space to occur is the weak link, the hop up/inner barrel securing parts. That is the problem you have.

LIL GING · November 10th, 2011, 23:51

so is there like a rubber bushing or somthing that could have got broken or do i need a new hop up?

MaciekA · November 11th, 2011, 01:11

I've debugged a bunch of issues with my hopups in the last few months, and a good procedure is to simply take your hopup and barrel assembly apart, give it a good clean, inspect all parts, and put it back together.

Remove the upper receiver, pull the hopup out, detach from inner barrel. Set aside. Use a tiny bit of tissue on your unjamming rod to clean the inner barrel. Do this a few times until you know the inner barrel is clean. If you fell off an ATV with your gun, it's going to be dirty anyway.

Then take apart the hopup. Remove the bucking with care. Inspect the nub. Look for any tearing or deformation. Put the nub back in the correct way. Here's a pic of the hopup from my PDW. You'll want to make sure your nub is oriented the way it is in the picture:

If your hopup isn't clear, just go real slow and ensure it is correctly in place using a flashlight. If you don't feel confident that it's correctly in place after you put the bucking and barrel back in, you can always disassemble the hopup, put the bucking and barrel in, and then reassemble the hopup arm while putting in the nub at the same time.

When putting this back together pay special attention to Stalker's advice and watch that C-clip carefully. Make sure you don't twist the barrel out of alignment with the hopup while putting it into your outer barrel.

When you get it all together, look into your hopup (have a flashlight handy) and inspect the shape of the bucking's protrusion. It should be pretty much a circle (assuming your hop is all the way off). Test turning your hopup on and off to ensure the bucking is coming in dead center. Here's a shot of me looking down my hopup / barrel in my PDW:

If you look closely you can see a little bit of funkiness with the shape. This is before I got it right. Keep testing.. It's really nice to have a chrono handy or at least a place where you can fire a distance while you're iterating through attempts to get everything working.

LIL GING · November 18th, 2011, 11:34

all fixed thanks everyone for the help (Y)

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November 10th, 2011, 19:52	#1
LIL GING Trader rating Join Date: May 2011 Location: Uxbridge,Ontario,Canada - or - NorthBay,Ontario,Canada	M4A1 shooting 2-3 bb's per shot? so i have a classic army m4a1 RIS system and it took a rough fall when i got flipped off a atv playing, and now it shoots 2-3 bb's everytime i pull the trigger. what could be the posible problem? could it be the hop up letting to meny in or a bigger problem and how could i fix this and get my gun back to normal?

November 10th, 2011, 19:59	#2
krap101 Trader rating Join Date: Jun 2007 Location: Roscoe, IL USA	I would say the problem is between the air nozzle and the bucking. My guess would be that the air nozzle isn't correctly seated within the tappet plate. __________________ AIRSOFT PRECISION DYNAMICS - Augmenting Reality

November 10th, 2011, 21:00	#4
krap101 Trader rating Join Date: Jun 2007 Location: Roscoe, IL USA	Are you able to disassemble gearbox or find someone who can? __________________ AIRSOFT PRECISION DYNAMICS - Augmenting Reality

November 10th, 2011, 20:29	#3
LIL GING Trader rating Join Date: May 2011 Location: Uxbridge,Ontario,Canada - or - NorthBay,Ontario,Canada	so how would i go about fixing that?

November 10th, 2011, 22:30	#5
LIL GING Trader rating Join Date: May 2011 Location: Uxbridge,Ontario,Canada - or - NorthBay,Ontario,Canada	yeah i know how to

November 10th, 2011, 23:03	#6
CDN_Stalker Official ASC Bladesmith Trader rating Join Date: Jul 2003 Location: Ottawa, Ont.	100% hop up issue, check that and don't bother with the mechbox, isn't the problem. Check the barrel seating in the hop up unit, and the rubber condition/setting. This is exactly what happens when the C shaped clip that holds the inner barrel and hop up rubber into the hop up unit cracks, its grip is lessened and when shooting the inner barrel moves forward a bit, allowing 2-3 BBs to load at a time. __________________ STKR Knives http://www.facebook.com/#!/pages/STK...17036668380871 Last edited by CDN_Stalker; November 10th, 2011 at 23:09..

November 10th, 2011, 23:18	#7
LIL GING Trader rating Join Date: May 2011 Location: Uxbridge,Ontario,Canada - or - NorthBay,Ontario,Canada	well i know when i shot it with out the interbarrel attached the nozzle pulls back into the gear box a bit could that be it?

November 10th, 2011, 23:23	#8
CDN_Stalker Official ASC Bladesmith Trader rating Join Date: Jul 2003 Location: Ottawa, Ont.	No, that's normal operation, the nozzle never rests at the full forward position after every shot. It's a hop up issue, trust me, I've fixed at least a dozen of these over the years, always the same problem, hop up. See, the way the system allowsonly one BB to be loaded and shot every time is the hop up nub, the thing that puts the back spin on the BB. It sticks into the barrel, the nozzle pulls back and one BB is let into the chamber and sticks there, the nozzle pushes forward, the next BB in line gets pressed down into the magazine, the nozzle sits full forward and the piston is released, pushing the BB out of the barrel. If the one BB amount of space between the BB feed and the hop up nub is increased to the space that will allow 2-3 BBs to enter, then they will. And the only thing that can allow that space to occur is the weak link, the hop up/inner barrel securing parts. That is the problem you have. __________________ STKR Knives http://www.facebook.com/#!/pages/STK...17036668380871 Last edited by CDN_Stalker; November 10th, 2011 at 23:27..

November 10th, 2011, 23:51	#9
LIL GING Trader rating Join Date: May 2011 Location: Uxbridge,Ontario,Canada - or - NorthBay,Ontario,Canada	so is there like a rubber bushing or somthing that could have got broken or do i need a new hop up?

November 11th, 2011, 01:11	#10
MaciekA Trader rating Join Date: Jun 2011 Location: Portland, Oregon, USA	I've debugged a bunch of issues with my hopups in the last few months, and a good procedure is to simply take your hopup and barrel assembly apart, give it a good clean, inspect all parts, and put it back together. Remove the upper receiver, pull the hopup out, detach from inner barrel. Set aside. Use a tiny bit of tissue on your unjamming rod to clean the inner barrel. Do this a few times until you know the inner barrel is clean. If you fell off an ATV with your gun, it's going to be dirty anyway. Then take apart the hopup. Remove the bucking with care. Inspect the nub. Look for any tearing or deformation. Put the nub back in the correct way. Here's a pic of the hopup from my PDW. You'll want to make sure your nub is oriented the way it is in the picture: If your hopup isn't clear, just go real slow and ensure it is correctly in place using a flashlight. If you don't feel confident that it's correctly in place after you put the bucking and barrel back in, you can always disassemble the hopup, put the bucking and barrel in, and then reassemble the hopup arm while putting in the nub at the same time. When putting this back together pay special attention to Stalker's advice and watch that C-clip carefully. Make sure you don't twist the barrel out of alignment with the hopup while putting it into your outer barrel. When you get it all together, look into your hopup (have a flashlight handy) and inspect the shape of the bucking's protrusion. It should be pretty much a circle (assuming your hop is all the way off). Test turning your hopup on and off to ensure the bucking is coming in dead center. Here's a shot of me looking down my hopup / barrel in my PDW: If you look closely you can see a little bit of funkiness with the shape. This is before I got it right. Keep testing.. It's really nice to have a chrono handy or at least a place where you can fire a distance while you're iterating through attempts to get everything working. Last edited by MaciekA; November 11th, 2011 at 01:13..

November 18th, 2011, 11:34	#11
LIL GING Trader rating Join Date: May 2011 Location: Uxbridge,Ontario,Canada - or - NorthBay,Ontario,Canada	all fixed thanks everyone for the help (Y)

M4A1 shooting 2-3 bb's per shot?

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