M16 / M4 Metal Body Problem

[nextmayor]

To start with I've got the Hurricane SR-47, but this problem could have happend to any M16 / M4 metal body, so please take the time to read this.

 

Any way, last March during a night game, I fell and really banged up my SR-47. The fall was so bad, that pretty much any part of the AEG that was held on with screws or threads loosend up. I got home and tightend everything up and the AEG appeared to work just fine, but the stock always seemed a little loose. There wasn't any wobble, just a little rotation. No big deal, I though, I'll just need to keep that main screw in the stock nice an tight.

 

Fast forward to yesterday. I decided to replace my bungie sling with a non-elastic 1 point sling. This meant I had to get a new sling mount due to the propriatary nature of my bungie sling.

 

So I pulled the stock off and then started loosening the screw in the stock tube. I immediately knew something was wrong, because once slightly loosend, the whole tube started to wobble. Well once the stock tube was completely off I saw one of the most horrible sights I could have imagined. Then entire stock extention tube coming off the receiver was completely broken off. This is the little cylinder with the flat wings on it that the stock tube goes over. Here's a pic of what I'm taking about. The tube that's broken off is in the red box.

 

 

Well I reassembled the stock with the broken part in place and the new sling mount in place. I was very surpised to find out that I really didn't notice any wobble. I held the AEG by the stock tube with the barrel pointing up and I could shake it pretty hard with no wobble or other ill effects. I thought maybe I'm okay. Well then I put the stock back on and noticed the the stock tube now spins against the receiver. I tightend the screw in the stock tube a little more and the problem went away but I don't know for how long.

 

I was just wondering if any other M16 / M4 users have every had this happen. Mainly looking to see if there is any way to fix this. Due to the weak and brittle nature of pot metal, I don't thing welding is an option. Additionally, I didn't know if epoxy or JB Weld would be stong enough to withstand the rotational force on the stock.

 

So right now I have some ideas, but I've really got to take a better look at the broken area. I was thinking about installing some set pins. For those of you familiar with CA metal bodies, think of the 2 small pins that engage the upper receiver to the lower receiver. I was thinking about putting 2-4 of these pins in the receiver and then they would slide into the stock tube. I've got the access to a machine shop and the ability to install these pins (provided there's enough material).

 

Like I said, I was just wondering if any other M16 / M4 user has every broken the stock extention off their metal receiver. If so how did you fix it. Best case would be to get another SR-47 receiver, but you can only get them in the kit and that costs over $500 (US). So that's not an option.

 

If I can't get this locked up, I guess I'll be forced to just get a standard M16 / M4 receiver and just make a pretend rifle. All I'll need to do this is a complete metal body and a hop up unit. The RIS, motor grip, mechbox, and stock will all fit on standard M16 / M4 recievers. To fund that, I'd probably just sell my AK mags, SR-47 Hop Up Unit, and hopefully the broken receiver. That's my last option. For now I am hopeful that I can fix this issue. Just wondering if anyone else has ever done this and how you fixed the problem.

 

Thanks.

[the cleaner]

hey Nextmayor,

 

I might have a solution for you. . what do you think?

 

There's alot of things to consider so this is just an overall "concept". . space available between the back end of the mechbox and the inside wall of the receiver is critical. .that will determine thickness of flange. . .the flange area does not have to be the entire dimension of the receivers rear. .

 

buffer tube plug portion is a no brainer. .just needs to fit to the inside diameter of the bugger tube.

 

 

[nextmayor]

Cleaner. That's a pretty clean and professional way of doing the repair. Time to head back to the machine shop for another night of measuring. Thanks for the idea. I'll add it to the list for more research. Nice drawing too, especially if you did it on the quick.

[the cleaner]

took me about 5 minutes to draw. .took me 15 minutes to figure out how to convert the Illustator file in a way that Photobucket can read it .. it won't take an Illustrator file that's been converted to a JPEG . .it worked converting it to GIF in web format. You would think a JPEG is a JPEG. . basically a photo image.

 

like I said. .you can have many different variations of the concept above. .. but the overall idea is the same. . .

 

I don't think there is a better solution than to tie the broken buffer tube with some fitting on the opposite side of the receiver. . JB weld definitely won't work in the long run. . and good luck welding/soldering pot metal. . .

 

EDIT: if you want to commission me to make the part. .I have my own SR47 to work off of.

[Magsz]

Just make sure that new part doesnt press the mechbox too far forward otherwise you may have some fitment issues with the mechbox against the hopup unit or feeding issues.

 

Ive never worked on an sr27 so i have no idea how much clearance there is behind the mechbox.

[BaBaBooey]

I would suggest you not try to fix it and replace the entire body - I know that sucks given it's a unique kit. You might be putting a lot of stress to the gearbox now since it sounds like you have your stock screw tightened a bit too much. It's essentially pulling the gear box backwards with more shear stresses to the gear box pin and front detent pin.

 

Chrono your gun and see if there's a huge fluctuation in fps - you may be good to go if it's steady and hasn't changed before the break. Also, check how hard it is to knock out the pins. You might also want to check the mounting screws for the grip as well. If it feels your putting way too much pressure, the gear box is taking too much stress (unless you have one of those CNC gearbox made of aircraft aluminum or something).

 

Hope this helps.

 

EDIT: read Magsz post - he makes a good point as well.