In 2009 I bought 3 sequentially numbered billet SI lowers which I put away and never used.
Then this year I bought 3 Midwest Industries billet uppers. They did not fit on the SI lowers. I contacted both parties and MI offered to exchange their billet uppers or even reimburse me if I was not satisfied. I exchanged the MI uppers as they are very nice but they still do not fit the SI lowers. They do fit other lowers. MI provided great professional and prompt customer service and support - they were great.
SI on the other hand informed me that the lowers were not covered warranty at this time.  They suggested I send them back to them. They also offered to match the MI uppers to the SI lowers.  I would be responsible for any shipping costs and labor associated with the matching.
I don't want machining and expect machines parts to be within tolerance.
Well the SI lowers don't work (cannot put the pins through) on Aero Precision, MI, Rock River or Colt M16 A1 upper.
I would of thought SI would have exchange the never used billet as it is obvious to me now that they are out of spec.
I guess some companies stand behind their product and others don't.
Hard expensive lesson.

While I agree in principle, and applaud MI for being a stand up operation, 5 years is a long time to expect someone to exchange product.

Rather than take a hit because you don't want "machining" why don't you let them fix them, since what you really needed to begin with was more "machining"?

If they are offering to make you whole as it sounds like, simply not the way you expect or require, five years in I think you are being a little hard headed.

I disagree with the guy above me...

How did they handle the serial number change?

They want him to pay shipping both ways plus labor on a part that is brand new.

I can see that. that however is a nominal cost to salvage 3 lowers that otherwise don't work.

I'm not saying it is a straight up deal, but before I took the sawzall to 3 lowers I would have them fixed, pay for it and move on.

Five years is five years, exchanging lowers with the serial number change, and the high likelihood that they have to involve a dealer to make the exchange could influence the decision.

Per ATF



 

bgenlvtex:
At the time, I bought them as a set of 3 sequentially numbered and for prosperity and future use.
Machining will result in oval lower pin holes (@ 9:00 o'clock when you look in from the pin insertion side.
These are parts machined by a company making mil spec aero parts. Being out of spec results most likely from poor machine programming?
Yes, 5 years later is quite a long time, but I never used them and assumed they were in spec. I guess that's my error - to trust the mfg.

Just to point it out; your lowers COULD actually be within 'Spec'...  The dimensional prints for an AR type lower have specified tolerance limits; meaning the pin hole shall be located here plus/minus X amount.





You may be experience a problem with tolerance stacking.  If your SI lowers are on the extreme end of the tolerance limits, and the rest of the industry is on the other, parts may not fit.



 

Correct, and again I am not defending SI.

So, what are you going to do with them? Personally as cheap as uppers are I would fit uppers to them and move on.Without looking at or measuring your lowers, I think I would drill oversize and plug the rear takedown hole with bar(upper), assemble the upper/lower using the front pivot , transfer the rear pivot to the plug with a transfer punch and drill to dimension. Pretty simple job with modest equipment. No permanent modifications to the serial numbered part.

My problem with tolerance stacking with the SI lowers is the OP tried several different well known brands and none of them would work. Uppers are built to accept a standard amount of tolerance stacking -- the SI lowers are just bad or may have been blems but they won't work with any AR upper found in the know world. I agree with you that the rear lug on the upper, that the OP want's to use, could be modified to work with the SI lowers.

edit to add; That's probably exactly what SI was going to do since they wanted the OP to send both the lower and the upper to them and they would make them fit toether.

Update:
SI has now proposed to check my lowers and pay freight etc.. I am sending them back for their dimensional evaluation.
A nice step in the right direction.

That's great!  



Be aware, they may be dimensionally within the specifications; doesn't mean they'll fit your other parts.