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Receiver bending while heating up the mag tube


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Hi, I have an M4 H2O. I bought a 7 round mag tube. I wanted to remove and replace the factory 5 round tube. I looked up how-to instructions on YouTube. I started heating the tube with a heat gun, then the receiver. It may be a quick heating job for a black M4, but the coating on the H2O took the heat for 45 mins before I got the tube to start turning. I discolored the finish on the receiver. I read that prolonged heat, while applying force to remove the mag tube, may bend the receiver out of spec. Anyone know how I can make sure I didn't bend the receiver? PS: Robar confirmed that the NP3 Plus dissipates heat, and also confirms that it could have discolored, so I decided to send it for a removal and reapplication of NP3 Plus.

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A quick, yet rather un-precise way of checking is to use an engineers ruler (really a metal straight edge) and gently lay it on the flats of the receiver. Any twist or deformity should be visible. Although not accurate, it should give you piece of mind that nothing is out of spec. Good luck with your project.

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Tests confirm the receiver will reach a maximum of 500 F with a standard heat gun. This number is reached on the High setting and prolonged time (about 45 minutes).

 

500 Degrees in no where remotely close to deforming aluminum. Also it is not close to tempering the metal since this process takes more heat and more time.

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Thank you for all your replies. I can't find any dimensional drawings, but would really like them. I used a metal straight edge, and it looks straight. It assembles, cycles, loads, and seems to operate (I have not fired it, because I packaged it and sent it to Robar for recoating due to bad discoloration). My concern is that I heated it, and also simultaneously tried to twist it using rubber-protected ChannelLocks. I keep reading that using strap wrenches while heating will result in torqued twists that can bend the receiver. I was also thinking that I should replace the bolt release button spring due to heat exposure. Would there be anything else that I should replace?

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Thank you for the replies. In addition to shooting properly, I'd want it to be intact, knowing that I didn't compromise springs, etc. I used a cheap Home Depot Wagner Model HT 1000 gun, 50/60 Hz, 120 VAC, 10 Amp, 1200 W. I also read somewhere that threads that are on the receiver will bend from prolonged heat exposure, but I was able to screw in the 7-round extension without problems. Any thoughts are appreciated.

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And, as a reminder, Robar told me that the NP3 Plus caused the heat to dissipate, resulting in the need for the 45-minute heating. The good news is that NP3 Plus seems to really work well... the bad news is that I probably should not have decided to modify an H2O shotgun. Too late, unfortunately. Too bad there are so few, if any, threads or experiences on message boards describing such experiences with H2O models, otherwise I would not have done it.

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Also, the paste was thick and white when the mag tube unscrewed. It came off with a terrycloth towel (because the threads of the mag tube and the receiver were both NP3 Plus coated). I didn't need to use Acetone, as described on many Internet posts. Am I nuts to think that the NP3 Plus is really that powerful? I mean, all the YouTube how-to videos show that you need to use Acetone and scrub, and that a little heat and hand cranking does the trick... just wondering.

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yea had I knowned how easy it was I took mine to a Marine who is a gun smith and that should have took no more than 5 mins Max 10 mins. he put little heat on it came right off. I am not seeing any problems that I know of. you should be ok try to cycle the gun drop 4 or 5 shells in there and cycle it real fast before you shoot it. (at the range tho). did you use blue locktight 242? when you reinstalled the mag tube? and also there's the plate that goes on the front of the receiver before you install that mag tube. they say drys few hours I let mine sit about a week was not going shooting anyway. let us know how it works out.

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Mine came right out and cleaned up great with just a microfiber rag also. No need for acetone with mine at all. I have just changed from a titanium mag on the M1014 to a OEM steel tube, and without using any thread lock before, the mag unscrewed with a fair amount of hand and body strength using a microfiber rag to grip with. Glad I didn't use loctite before.

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Thank you. I replaced the tube, reinstalled everything properly, and tested to make sure it cycles. I am not planning on using any LockTite (so that I can remove the mag tube for cleaning in the future). I don't visually see any problems, but I my main concern is damage assessment and damage control, regarding my looooooong heating of the receiver, the threads, the springs, as well as my concern about the potential damage caused by torque post-heating and ChannelLock-turning. I am refinishing the gun. I wanna make sure I didn't move it out of spec or create an unreliable home defense shotgun. It seems like people with the black shotguns don't experience this problem. Anybody with an H2O have this problem, or figured out how to avoid it?

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Yes use the Blue Lock tight 242 you don't need to take the mag tube off once installed just to clean.... the blue comes right off probably with a hair dryer. ( don't use the red or the Green ) than you need heat to take it off with thoes 2. stock it comes with Green lock tight... that's the strongest... set it and forget it. because of you don't and your at the range you going to have to keep on turning that tube just to make it tight again... ( Clean the inner threads before applying the Lock tight ). save your self the problems...

http://www.waresdirect.com/products/Commercial-Products/Loctite174;/Threadlockers228485?trackURL=froogle&gclid=CMbfqLOE-rwCFTBk7AodXXgAZw

Edited by Hardcharger
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Damn,.........45 mins?! Holy ****!

 

Assemble the M4 and ensure it operates properly, I have yet to see a dimensional drawing of the receiver, that is what you need though.

 

No kidding!!!! I'm sorry, OP, either they changed the formula of the adhesive, or you weren't trying very hard to turn the tube, or you were heating it in the wrong spot, or a combo of all 3. No way NP3 dissipated that heat that way. If you don't believe me, run 3 mags down it and grab the barrel just forward the chamber. I bet it still feels warm...

 

As to the receiver being tweaked, remove the BCG/FCG, and slowly insert the barrel. If it properly slides into place snugly without slop or un-due force, then you just verified that all is well as far as you should care, up top. Now, slide the FCG in and lock the pin through it that holds it in place. Did everything go as reasonably as it should? The bottom is fine, then.

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Hello, thank you for the replies. It loads, and it cycles. The barrel slides in properly. Everything seems to work. I am only relaying what others have told me, regarding heat dissipation. I heated the tube for 20 minutes, then decided to heat the receiver for 25 minutes. It was a long process, and I used focused heat. I just wanted to make sure I didn't bend the receiver nor the threads, and I also wanted to make sure that I didn't weaken the springs, etc. Any thoughts?

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I heated my receiver until the tube was removable. It may not matter, but heating the male part of a threaded connection is not the ideal way to remove stuck or very tight tolerances. Making the female part expand with heat while not expanding the male section makes the connection not quite as close in tolerances. I have seen the male part of a fitting frozen to shrink it and the female heated to expand it. That's the theory I used in heating and removing my original mag. Then I went back dry with just the warmth of the receiver and no loctite. I used no tools, just a microfiber towel. And there is no hurry. The metal holds the heat well. Just remember, if you screw the new cold mag tube into the receiver while the receiver is hot, it may be difficult to remove next time unless you reheat it.

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