Building a 10/22

6061 is not "aerospace specification" any more than leather boot laces, spruce sticks, or canvas are. Yeah, they use some 6061 in airplanes. And it's hard to beat if you want a material to make beer cans out of. But a reciever in anything short of 7075 I would not buy.If they don't want to pay the extra $5 to start out weith a decen 7075 blank instead of 6061, I would not buy from them- unless I supplied my own blank.

My ,02. And yes, I know it's only a .22 but still.....

Depending how custom you want, Volquartsen makes similar. Pricey, but good- probably not 6061 although I can't say for sure.

Starting off with any major parts out of 6061 will result in either project failure, project dissatisfaction or additional cost of replacing these parts during or shortly after the build.

I looked at the same web site about a month ago, thought this would be a fun build, then I sat down and figured the cheapest receiver was 130 dollars the drill bit kit and drill fixture and it was around 200 dollars, so what I did was to buy a 10/22 receiver from gunbroker for 65.00 and had it shipped to Bruce at Hunters Essentials. For the money I saved I went with 17HMR new .920 barrel and brake, 17HMR charging handle, I already had a few trigger groups laying around so nothing was spent for that.
Had the SelectFire receivers been less money I would have thought about it, but when you add it all up you'll have a $500 10/22, plus optics, buy a top of the line 10/22 and still save money.

Try either a Volquartsen or a KIDD receiver http://www.coolguyguns.com/RiflesReceivers_c_10.html, there are also steel receivers on the market so if 6061 aluminim is a worry thing steel. There is also the issue of free floating a barrel off an aluminum receiver, although I have never seen a cracked receiver because of it, it does happen. One other thing the SelectFire do not have serial numbers, so that may be an issue should you ever decise to sell it.