HKPRO Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Like most new folks on here i have been reading and reading and scouring the internet and have finally come to a question i cannot find the answer to. i want to explain thoroughly so this post may be kind of long so thanks ahead for everyone's time. Im building an mp5 clone from a German A3 parts kit and am using a clipped and pinned navy style trigger group. I had completely finished the build in all areas accept for the finish but i had a small gap in the cocking tube butt weld where i stopped and re-positioned to complete the weld (i did not spot weld/plug weld the side of the cocking tube sleeve like i understand is done on factory hk builds). I did several functions checks, made sure it cycled properly and ensured that magazine fit was acceptable and then prepared to apply the finish. Then i noticed the gap and couldn't leave well enough alone so i decided to trace over the butt weld without filler with low heat (about 20 amps) to fill the 1/32in gap for cosmetic appearance. BIG MISTAKE! After i finished this i decided to do one more check of the fit for the cocking tube support inside of the cocking tube and DING! it stopped about an inch short of fully seating. I instantly felt nauseous. I began to check for the problem and noticed that the fully round aft half inch of the cocking support appeared to be getting stuck either at the beginning of the cocking tube sleeve or slightly inside of it. It felt like a problem that would come from a bent cocking tube causing the aft end of the cocking support to be dragged either against the top of bottom of the sleeve cause it to bind up but everything appeared straight. no obvious bulges caused from welding heat and no flattening of the beveled end of the cocking tube. I cannot figure out why this was happening but it was apparent that it wasn't right so i removed the cocking tube and barrel/trunnion. I was using an aftermarket cocking tube and not a demill and was using a piece of copper round bar turned down to fit through the cocking sleeve to about 1/8in past the butt weld to prevent burn through. I need to figure out why this happened so i can prevent it with my next attempt. Im asking a lot of people to help solve a problem they cant see when i couldn't figure it out with it right in front of my face but i figure that some of you have probably seen it all including this problem. Is it imperative that i do the plug welds on the side of the cocking tube sleeve (i have no ability to spot weld it) and if so whats the best way to prevent distortion from weld heat? Thank you to everyone for your time. I know this is a long one but any advice on how to proceed without this problem occurring again is very much appreciated.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #2 ·
Well I know this is a long one so I will shorten it up. When welding the cocking tube do y'all use the plug weld on both sides of the cocking tube behind the butt weld and if so what order do you weld the CT? Tack the plug welds on the side then tack the butt weld on both sides and then on top or is it butt weld first then plug welds. Could anyone with a moment to spare give me a detailed idea on how to approach this portion of the build? I'm finding lots of good info on here but nothing with the CT details I'm having trouble with. Any info would be very much appreciated.
 

·
Registered
Joined
·
101 Posts
This information is off the one time I did a mp5 clone build. So with that in mind I would never purposefully give out wrong information but since no else will help here's what I would do. The cocking tube has a depth at witch it sets in the receiver and I don't remember the measurement. Need heat sink inside cocking tube and receiver. Need alignment jig in front sight tower to cocking tube. I used the three plug welds also. In no order I welded a tack in five spots. Like one on right, then one one left, one on top, so on. Always checking for straightness. Also when its just tack welded in a few spots you can check for parts fitment. Tig on low heat. enjoy
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #4 ·
Thanks for your help gamble i really appreciate it. Just to make sure i understand, are you saying that you did do the 2 plug welds through the side of the receiver to the CT sleeve? when you say low heat after a couple tacks are we talking 35-40 amps or are we talking as low as you can go and still melt filler at between 10-20 amps. once again thanks for the help
 

·
Registered
Joined
·
101 Posts
Your right it is two plug welds. Its just been so long I was thinking there was a plug weld on top. All I can say is practice with your welder. Use material that is the same thickness of the thinest part of the cocking tube. not all tig welders are equal. So I don't want to say how many amps and you fubar your expensive build up.
 

·
Registered
Joined
·
101 Posts
Cool there you go hurry and call ghilliebear before he change his mind, he builds clones for a living. Your very lucky he reply.
 
1 - 7 of 7 Posts
Top