View Full Version : Those Durafix aluminum brazing sticks really do work on ARs/M16's

02-12-2013, 9:59 PM
Just thought I would share this in case anyone with an AR ever needed metal repair. Those brazing durafix or whatever aluminum brazing sticks really do work. I thought I would just share my experience on it.

This is what I started with on the m16 project


This is when I first brazed on the magazine well on it.


Notice that it is gray and frankly, looks like a mess. After the braze sits for a while it turns gray like that. If you polish it, or run it over with a wire wheel (which is what I did here), it shines up.



I purposely left the seam think and kind of sloppy. The deal is that when you braze one part of the receiver, it heats up the entire receiver which may make what you just put together want to melt a part. The way to fix that is just to make the "weld" thick, so when you heat another part of the receiver it won't melt.

Once everything is put together, I will grind it down.

I tried grinding down just a portion with the sandpaper thingy on a dremel to demonstrate what I am talking about



It really does grind smoothly so that I can't tell where the "weld" begins and where the original metal begins. Once this is together, I have no doubt that I could get it to the point where no one could tell by visual that it's been put back together.

I was screwing around with the "weld" on the receiver and other things I put together. That stuff is actually pretty strong. I think it is probably just as strong as the original aluminum, if not stronger. Things I've put together with it, I can't pull it apart.

The stuff is more elastic than aluminum. Like on the aluminum of a reciever, if you try and bend it, it will crack. The brazing stuff you can actually bend it (to some extent or another).

I had problems using it at first. I had stripped off the anodizing with lye. When I first tried using the braze it was heating up, but just not sticking. I had to use the dremel with the sandpaper wheel to take off a top level of the receiver surfact in order to get it to stick. I think there must be some anodizing or oxidation on the top which prevents it from sticking. It usually recommended to use a stainless steel brush prior to brazing, but that's still not enough. You have to remove a top layer of aluminum to be able for this stuff to stick. And it has to be hot in order to stick. But once it does stick, it does really work as advertised.

It is a little sloppy to use however. It does liquify easily so instead of sticking together it has a tendancy of liquifying and spreading all over the place. You have to get used to it to really be able to control it.

I put on one side of the magwell so I needed it in place to align the take down pins with the front and back. The magazine test fits into the repaired side of the magwell. And with the rear clamped in place, the rear lines up as well.


I am also using a spare side from another demilled receiver to align the holes.


I can't attach the rear portion of the receiver with the buffer tube until the holes for the autosear are welded shut (no braze will not be good enough for that). So it may have to wait until that is done.

02-12-2013, 10:11 PM
where did you ge tthe demill from? good luck looks like alot of work. if you have a mig you can get alluminum feeding kits for them. might be easier. or a tig would be waaaayyy easier.

02-12-2013, 10:21 PM
It's really not that much work. Once it's clamped then just have to brace the rear, and then the right side magwell.

The demil is from Apex (the front part mag well) $15. I was just going to cut out the roll marks and weld/braze on an 80% receiver. The rear half of the receiver was bought on gun broker for like $40. Considering an 80% was around $100, plus having to rent a mill for around $75, i though I would try just putting back an original receiver. If it didn't work I would just cut out the roll marks but, so far it's working. Really, it's not that much work. Once you get the hang of it, I could probably put this thing together in a day.

I would use a mig or tig, but I don't want to spend the money for the equipment just for one receiver.

02-12-2013, 11:13 PM
I would fill that naughty hole first before you go any further.

02-13-2013, 2:11 PM
^^ second that!!!!

02-13-2013, 2:28 PM
Lol again about the hole

02-13-2013, 2:34 PM
Have you considered making and attaching a heat sink to the parts of the receiver that you don't want to heat up when you're brazing? It might help your existing joints stay stable during additional brazing operations.

02-13-2013, 2:40 PM
Use a tactical machining side plate for jig.

02-13-2013, 6:33 PM
Lol again about the hole

:) The hole. Always with the hole. On another thread there's been significant...uh..."heated dicussion" about the hole. Yes, thanks to kcstott, the hole will be welded shut so there will be no issue. I am mailing him the rear end to be welded, and the rear end will not be attached until the hole is taken care of.

And grumpyoldretiredcop, thank you very much for the heatsink suggestion. I am going to look into that. I think it will help. Do you have any internet links of the kind of heatsink that you were thinking of? (I just did a search and there are a bunch of different hits with the words "heat sink")

02-13-2013, 8:33 PM
Try clamping it to a large piece of steel. That should be a large enough hear sink without getting too extravagant.

02-13-2013, 11:38 PM
Clamping it to a chunk of steel might work, I was thinking about something more fancy like a chunk of aluminum shaped to fit into the magwell or fire control well. All you're looking for is mass that the receiver can transfer heat to. It will have to make contact with the receiver over as much area as possible, hence my thought about shaping a block to fit into the magwell.

I've never seen anything specific for an AR receiver.

02-14-2013, 6:30 PM
Clamping it to a chunk of steel might work, I was thinking about something more fancy like a chunk of aluminum shaped to fit into the magwell or fire control well. All you're looking for is mass that the receiver can transfer heat to. It will have to make contact with the receiver over as much area as possible, hence my thought about shaping a block to fit into the magwell.

I've never seen anything specific for an AR receiver.

I don't think I'd use aluminum as a heat sink. It might get hot enough for the brazing rod material to stick to it. I had to repair my RAW receiver many years ago & used an aluminum brazing rod. I backed up the area I was brazing with a thick (about 1/4") piece of copper. I read somewhere that nothing will stick to copper when welding. Not too long ago I used it when mig welding and sure enough nothing stuck to the copper even though the welded area was touching it.

Would love to try a project like yours or at least have the complete pieces from an M16 lower. Bit of history! :oji:

02-14-2013, 7:36 PM
I do believe that you have a point. Shows what I know about welding/brazing... which is just enough to get into real trouble. :D

Obviously a Plant
02-14-2013, 7:48 PM
For sweating copper pipes, one can use a wet rag tied tightly around the pipe on either side of the join you are working on to prevent the surrounding solder from melting too.
Water has a phenomenal capacity for heat, something similar might be worth a try (copper is a good place to start too...)

02-15-2013, 7:46 AM
In the tool room and now at home when I have to weld next to a virtual area, feature, hole, etc. I use copper rod or plate, or graphite. You can weld right put to and on top of the backer rove when cool and I looks like a machined edge almost.