Piston Stuck in the Back

Gen. Hospital · May 7th, 2008, 16:53

I took the gearbox in my hk416 apart, intending to put in some new stuff, only to discover that the bushings I bought don't fit. I put it back together and set it aside for a few days, but just now I felt like doing a bit of shooting. About halfway through the second mag (150 or so shots), it stopped working. Picked it apart to discover that the piston is stuck to the rear. Now obviously I'll need to open the gearbox to find out exactly what I did wrong, but there's a pretty angry spring in there, and I'm unsure how to proceed. Any pointers? :???:

Roughneck · May 7th, 2008, 17:03

Carefully, I've opened a V2 mechbox with a charged spring before. I unscrewed everything and then lifted the back end of the mechbox up so the spring and piston would go forward, instead of across the room. Before opening, I would also try charging a large battery to full and try a single shot.. that sometimes free's it up. I'm no gun doc though

The Saint · May 7th, 2008, 17:06

There's a hole in the base of the spring guide. Carefully pry open the mechbox just enough to run a screw driver into that hole to hold the guide in place. Don't forget to also hold the cylinder down. With both the cylinder and the spring guide held down, remove open the mechbox completely and carefully remove the spring guide.

Tex · May 7th, 2008, 17:13

to add to the saint's post do that inside a large ziplock freezer bag or anyother clear bag so if something does spring out you won't loose it.

Gen. Hospital · May 7th, 2008, 17:14

Thanks, both of you. I was kinda hoping there would be some pagan ritual or something I could perform first to release that spring. Ok, I guess I should just put on the goggle and get cracking, then.

EDIT: Yeah, I'll get a bag. Thanks :-)

EDIT some More: And I tried "charging a large battery to full and try a single shot..". Now I have a stuck piston and a blown fuse. :-)

Roughneck · May 7th, 2008, 17:35

Quote:

Originally Posted by Spencer

I'm no gun doc though

That's my disclaimer, my apologies just the same though. It has worked for me.

Jimski · May 7th, 2008, 17:44

what about catching the anti-reversal latch and pulling it ?
not sure you can on a v2

Gen. Hospital · May 7th, 2008, 17:54

I could. There's a hole right next to it, so I used a torx driver on that sucker.

Turns out the piston was unscrewed from the piston head.

ybrik · May 7th, 2008, 18:43

On a v2 mechbox, I would insert a bent wire (shaped to an "L"). Insert in on the motor pinion gear hole and catch and pull the ARL. Spring will be released and piston fully forward.

ThunderCactus · May 7th, 2008, 18:51

I bent a nail 90 degrees at the end and use that to get to the anti reversal. Works great lol
You can try a small hex wrench too but that takes some doing.

ybrik · May 7th, 2008, 18:55

Does this also work on a v3?

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May 7th, 2008, 16:53	#1
Gen. Hospital Trader rating Join Date: Apr 2008 Location: Norway	Piston Stuck in the Back I took the gearbox in my hk416 apart, intending to put in some new stuff, only to discover that the bushings I bought don't fit. I put it back together and set it aside for a few days, but just now I felt like doing a bit of shooting. About halfway through the second mag (150 or so shots), it stopped working. Picked it apart to discover that the piston is stuck to the rear. Now obviously I'll need to open the gearbox to find out exactly what I did wrong, but there's a pretty angry spring in there, and I'm unsure how to proceed. Any pointers? :???:

May 7th, 2008, 17:03	#2
Roughneck used to be Spencer aka Sue Trader rating Join Date: Oct 2007 Location: Halifax, NS	Carefully, I've opened a V2 mechbox with a charged spring before. I unscrewed everything and then lifted the back end of the mechbox up so the spring and piston would go forward, instead of across the room. Before opening, I would also try charging a large battery to full and try a single shot.. that sometimes free's it up. I'm no gun doc though __________________ Tpr. Spencer, DF RCD C Sqn - CFB Gagetown Please save for me, some gallantry That will echo when I'm gone

May 7th, 2008, 17:06	#3
The Saint Trader rating Join Date: Jan 2005 Location: Quebec	There's a hole in the base of the spring guide. Carefully pry open the mechbox just enough to run a screw driver into that hole to hold the guide in place. Don't forget to also hold the cylinder down. With both the cylinder and the spring guide held down, remove open the mechbox completely and carefully remove the spring guide. __________________ "The Bird of Hermes is My Name, Eating My Wings to Make Me Tame."

May 7th, 2008, 17:13	#4
Tex Trader rating Join Date: Feb 2003 Location: Abbotsford, B.C.	to add to the saint's post do that inside a large ziplock freezer bag or anyother clear bag so if something does spring out you won't loose it.

May 7th, 2008, 17:14	#5
Gen. Hospital Trader rating Join Date: Apr 2008 Location: Norway	Thanks, both of you. I was kinda hoping there would be some pagan ritual or something I could perform first to release that spring. Ok, I guess I should just put on the goggle and get cracking, then. EDIT: Yeah, I'll get a bag. Thanks :-) EDIT some More: And I tried "charging a large battery to full and try a single shot..". Now I have a stuck piston and a blown fuse. :-) Last edited by Gen. Hospital; May 7th, 2008 at 17:18..

May 7th, 2008, 17:44	#7
Jimski Trader rating Join Date: Jun 2005 Location: Montreal	what about catching the anti-reversal latch and pulling it ? not sure you can on a v2 __________________

May 7th, 2008, 17:54	#8
Gen. Hospital Trader rating Join Date: Apr 2008 Location: Norway	I could. There's a hole right next to it, so I used a torx driver on that sucker. Turns out the piston was unscrewed from the piston head.

May 7th, 2008, 18:43	#9
ybrik Trader rating Join Date: Jun 2007 Location: Ontario, Canada	On a v2 mechbox, I would insert a bent wire (shaped to an "L"). Insert in on the motor pinion gear hole and catch and pull the ARL. Spring will be released and piston fully forward. __________________ 5.56x45mm + m27 = M249(SAW)

May 7th, 2008, 18:51	#10
ThunderCactus Not Eye Safe, Pretty Boy Maximus on the field take his picture! Trader rating Join Date: Feb 2007	I bent a nail 90 degrees at the end and use that to get to the anti reversal. Works great lol You can try a small hex wrench too but that takes some doing.

May 7th, 2008, 18:55	#11
ybrik Trader rating Join Date: Jun 2007 Location: Ontario, Canada	Does this also work on a v3? __________________ 5.56x45mm + m27 = M249(SAW)

Piston Stuck in the Back

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