Interesting question. I have never experienced it, but I guess I would either clean the broken area with acetone or alcohol, cover it with flux, then use brazing wire to fill the gap. If the gap is too narrow I would file it wide enough, clean with alcohol or acetone, flux, braze. To mitigate the need to re-drill the hole, insert sacrificial 2.5mm drill bit and rotate it continuously while brazing. Just a guess from my part. Never neen forced to tackle this scenario.
Pieces of aluminium, or aluminium extrusions, can be bought at most hardware retailers or machine shops. You might need to pay a bit more if you buy it from a machine shop, since they need to make their profit, but it is absolutely doable. I got my aluminium from an online website for second hand goods. You can find it through a myriad of sources.
Unfortunately that's only a Wei-Tech M4 lower receiver. Here are some real receivers: instagram.com/p/BbZqWHqBosc/?igshid=1p3pnopfx3ihl Look out for these, and more, in coming videos.
Buying a complete replacement is always a good idea, but if you are quite the rambunctious player, you might cause further damage down the road, and having a spare is always the best option. And also, I am cheap.
