M14 receivers

[Fang]

Stumbled across this site (http://www.762mmfirearms.com/), which appears to belong to a manufacturer I've never heard of, yet who makes M14 parts. Their receiver prices seem suspiciously good, too: $500 for a cast receiver and $700 for forged. Naturally, they say that they are manufacturing parts based off specific drawing numbers, but this says nothing about how closely they stick to spec.

Still, it's tempting. I've wanted to build an M14 for a long time, and if these receivers are good then they provide an opportunity to do so sooner than expected.

[Clinotus]

Enough time has passed that surely you have moved from the 'this might be a good idea' phase, to the wondering how quickly it will arrive phase.

(hint,hint)

[ddeaton]

this company has not turned out a finished reciever yet. The guys on the M14 forum are waiting on a group buy which is late now. I am waiting on feedback before ordering one. Payment up front.

[Fang]

Sounds like a prudent course of action. There are so many ways to go wrong with an M14 receiver that I admire the courage of those buying sight unseen.

[Cyrano 4747]

Sounds like a prudent course of action. There are so many ways to go wrong with an M14 receiver that I admire the courage of those buying sight unseen.

So what are the big problems with M14 receivers? Are they just really dimensionally finicky and hard to get right or something?

What makes them so challenging when it seems, for example, that any monkey with a CNC machine and some aluminum stock can make acceptable AR receivers?

[ddeaton]

Apparantly they are a little finicky. They crashed a custom broach that is special order from what I heard. I hope they get it together and turn out some nice stuff. The first good word I hear about them I will be all over one. I am on the waiting list at LRB which is 9 months now.

[Fang]

So what are the big problems with M14 receivers? Are they just really dimensionally finicky and hard to get right or something?

What makes them so challenging when it seems, for example, that any monkey with a CNC machine and some aluminum stock can make acceptable AR receivers?

I don't know enough about machining to say whether or not any parts of the M14 receiver are particularly challenging, although I will say that the consistency of AR receivers probably has more to do with well-known specs, variety of parts relying on being in spec, and the volume of competition ready to take customers who flee from one's poorly-QAd lower than being particularly easy to machine.

That said, there are a couple potential problem areas. The bolt lugs in the receiver have a helical cross-section that provides the primary extraction, letting the bolt back out under rotation slightly so that static friction between the case and wall are broken before the bolt pulls straight back.

More important is the firing pin camming bridge, which is responsible for pulling the floating firing pin back as the bolt moves forward, and only releasing it once lockup begins. If this is machined too far back it runs the risk of breaking the firing pin, extractor, or frame bridge. If it's too far forward, the risk of slamfires goes up.

There's also the sight base on the rear of the receiver. This has to have its ears machined perfectly parallel, with grooves on the ears for the adjustment knobs, and the entire thing adds one more part that needs to be even with both horizontal and vertical planes, or the point of impact will move in two dimensions when adjusting only one dimension on the sights.

[Danube]

Good info to know. Did you build one prior or are you just looking to build?