Question about my new upper...

[Creeky73]

so my Sun Devil flat top finally got here, and I am having a little problem. Granted I am not a gunsmith, and I knew that at the very least I would need to have all the barrel stuff swapped over by a professional. But I took off my old upper just to see how well the SD unit fits, and...it doesn't. The front pin nearest the magazine well is just fine, but it simply will not fully close to the rear pin, and this is with or without the bcg in it. Is a little massaging of the parts to make them fit common, or is this bad news right off the bat? I have a Rock River lower that I am putting it on. Should I just go ahead and drop the cash on a new lower as well? And can someone give me a second job so I can afford my AR-15 fix please?

The unit looks great, appears to be very high-quality and the walls are really thick. Only one other negative: my unit did not come with the Sun Devil logo on it. Yes, it is a ridiculous thing to complain about, but for anyone who cares, just be aware. No logo on mine.

[federalist22]

I just got my Sun Devil upper receiver from Rainier today--also did not have a Sun Devil logo on it. I will be fitting it to a Seekins Lower in the next week. Hope I have no issues, but will provide feedback.

The Rainier pic has a logo on it: http://www.rainierarms.com/?page=sho...roduct_id=1079

[Creeky73]

I just got on the wait list for the POF Gen II. I am wondering if it would be smarter to get the Sun Devil lower, just to ensure fit. The SD unit is cheaper, and it is also machined billet, but it looks very much like a typical forged lower from what I can tell. I kind of feel like if I am already spending the cash, I might as well spend a little more and get something nicer.

[federalist22]

I just tried my Sun Devil upper on a S&W M&P lower and it fit. I will let you know about how the fit goes on the Seekins when I pick it up from my FFL.

[Creeky73]

well I was sort of hoping for a little more feedback on this issue. I figured there must be a metric ton of ppl on this board that build their own AR's from scratch and could give me some enlightenment on whether or not fitting issues were common or something that signals a problem right away.

[federalist22]

I will say that My Sun Devil upper is a tight fit on my Seekins lower, but I attribute that to higher precision machining specs to eliminate play. I am sorry I don't have any more info here. Maybe Stickman does.....he has all kinds of uppers/lowers and has probably seen this before---or, it could be a real problem.

[Creeky73]

yeah I am not sure what to think. It appears to me that there would have to be a little work done to my stock lower or to the new upper to fit right, and I don't want to do either. I think I will go ahead and order a new lower, and if they don't match up well, I'll go ahead and have the work done. Thanks for your help :)

[Stickman]

I'm not sure how I missed this thread.


When you say it won't fully close on the rear pin, what do you mean?

Does it close, but the rear pin won't go through?

[rebelEMPIRE]

From my personal experience, billet receivers as opposed to forged receivers tend to have a tighter fit. It's often necessary to give a bit of assistance (tapping) in pushing and pulling the take down pin and pivot pin. Whereas, forged receivers, I can simply push with relative ease.

It almost sounds like you have one of two problems: Either the flat surface where your upper meets your lower is slightly askew, or one of your pin bores has been reemed incorrectly--possibly mislocated.

If the fit is so terrible that you cannot make it work somehow, Rainier Arms is selling T15 forged lowers right now (on sale) for ~$110 a piece. I just bought one because the price is hard to resist. Everything about this lower is excellent except for the overall finish; it isn't perfectly smooth on forged surfaces.

-rebelEMPIRE

[Creeky73]

When you attempt to close the two pieces, you can actually see a gap that light will shine through beginning about midway through the flat spots from the front pin, and continues all the way around the curve at the rear of the receiver. The pin will ALMOST start to go in, but no go. The front pin fits in fine, so I am assuming that the rear pin will as well, when the two holes line up correctly. There have not been any alterations to the lower or upper at this point, it is a stock RRA lower. I was a bit opposed to tapping them together, as it appears that there may be some metal-on-metal contact that is keeping the two from closing. You can see some slight friction marks where the black finish has been scratched away from the rear tab of the new upper, the tab that the rear pin goes through, almost as if at the very top of the tab, it gets just a bit too fat to allow the rear of the upper to close all the way. I have pretty much made up my mind that I am gonna sleep on this until I buy a nice lower, and I will see if I have the same problem then.