1st AR build from 80% reciever

[JimTh]

So I am now getting into the build an AR with an 80% blank. I know some on this forum have done such work and I need a question answered. The build guides are specific with depths giving depths to the thousandths of an inch. This seems almost like an impossible task...but people do it without a CNC machine. Just how critical are the tolerances. No need to tell me I can be a couple of thousandths out here or there lest that become my new bench mark. I just don't understand how to cut that closely with a drill press but they seem to do it on youtube. All advise is welcome.

 

[Stengun]

Howdy Jim,

As a shadetree wannabe machinist I just do not see how a person would machine out the trigger group area with a standard drill press.

It would be pretty tough to do it on a quality mill/drill.

As with most of my "projects" I machine them oversize/undersized and then polish to fit.

After thinking about this:

I guess if a person would rough drill the TG area making sure it was vey undersized then using a dremel, files, needle files, etc it would be possible be would take many, many hours to complete.

I guess the only really critical areas would be where the TG pin holes are located. This would be the inside dimensions of the lower.

Also the pin hole(s) would have to be in the EXACT locates for everything to work right.

It's doable but would take an incredible amount of time and patience to do.

At the last gunshow I was at there were literally 100's of lowers for under $70 out the door. Heck, for $75.00 you could buy them from an individual without paperwork.

If I was worried about a paper trail this is the route I would take instead of try to build an 80% lower without atlest a mill/drill.

Paul

 

[JimTh]

Paul...now-a-days when you buy an 80% lower you had better get the jig set up too. We got the jig but my problem was the depth tolerances. I mean when they list the depth to a thousandth of an inch you had better have a really good caliper. So I think all is under control. I did get bit stops to make sure the depths were correct. It is always easy to take more material off but you aint gonna get it the other way around. This is a fun little project and uncle sam doesn't have to know. Oh I can buy a complete lower if I screw this one up. Might just do that because the complete uppers have been shipped. This was my wifes idea anyway. I see it as a challenge worth undertaking. It aint like I am flushing money down the toilet...a paper weight if all else fails.

 

[Stengun]

Howdy Jim,

If you already have an AR or a lower, complete or striped, plus a lower parts kit you can always do the old "grind, file, sand and polish until it fits" method.

That's what I do with my machining work.

Worst case is you end up with a paper weight.

I'm a "Why buy it when I can build it!" kind of guy so I understand wanting to build one yourself. Heck, I built a car in my shop from a pile of steel tubing and a cut up fiberglass body.

Here's a couple of
Pics of it:

[

I still have a long way to go before it finished but I'm slowly getting there.

Good luck with your project and post a few pics of it when your finished.

Even with Our screwy gun laws We are still allowed to build a gun for our own personal use without having to get permission.

I've always wanted to build a non-metal 2-shot derringer in something like a .32 S&W short or a .22LR penguin. Maybe in the future but right now you slate is completely full.

Paul