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Posted: 1/13/2005 2:35:30 AM EDT
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AR15 Upper Receiver FAQ Folks, I'm currently working on putting together a new FAQ. I will eventually have pics and such, but for now, I'm looking for feedback on the current text, and for any questions you would like to see answered in the FAQ. Please keep those questions limited to AR15 Upper Receivers. Please post your comments here, so that we don't duplicate any work. Yes, I'm well aware of the FAQ at Biggerhammer.net here (I contributed to it), but despite the great pictures, some of the technical data is either misleading or outright incorrect, and most of it dates from '98-'99. It is also very Colt-centric, but for upper receivers, that doesn't matter so much. I'm trying to build something a little more complete and as close to 100% correct as possible. Your help in this will be appreciated by all. Thanks for looking. -Troy |
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Great effort, Troy. I have often though of doing this, but with everything else going on, I haven't had the time to put an honest effort into it. While I didn't read every detail, it looks good so far. I'll give it a thorough read later and provide feedback if needed. |
I thought about putting that on the chart, but I decided it would be too confusing, so I'm going to add that info in a written paragraph. Colt: "King Of The Exception" strikes again. -Troy |
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Troy, check out this thread if you haven't already.... www.ar15.com/forums/topic.html?b=3&f=12&t=219378 It looks like there may be a way to identify Cerro Metal raw forgings to a specific manufacturer. |
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Troy, I may well be incorrect here, but I thought I'd mention something anyway.  According to your chart, A1s have the forward assist but no brass deflector. As I've always understood it, this configuration actually belonged to the XM16E1 -- sort of an in-between prototype between the M16 and M16A1 variants. A1s have both the deflector and the FA. At least that's how it was 'splained to me by and old Vietnam infrantry officer when I was building up a replica. Great resource you're putting together here. I'll check back periodically to see how it develops. -SC |
Keep up the most excelent work!
The XM16E1 was the prototype of the M16A1, yes, and many "A1" features were transitioned in during the XM16E1 period, and a few more came in after the formal transition. But no A1 upper ever had a brass deflector. Those first appeared on "A1" uppers when the Canadians designed their C7 rifle, which was a mix of M16A1 and M16A2 features. Thus, I have listed the C7 upper as having the BD. The BD was first seen in the US with the adoption of the M16A2, of course. Some actual M16A1 pics:    Note that these lowers are fully fenced; the only slab-side M16s were the Colt Model 601. The 602 had the pivot pin detent channel but no mag release fence, and later models were fully fenced. -Troy |
Or, more correctly, to a specific subcontractor. Think "Yankee Hill Machine"... -Troy |
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Great work Troy, having done this type of thing before I know how much work it is. I had thought about doing something along these lines on USGI bolt groups myself. Your upper guide looks really good, I only found three things to nit pick on (and I combed it over good, hehe): "The AR15 was first produced in 1960" Colt's first production batch started in late 1959. Purdy darn close to 1960. "When Armalite engineers Jim Sullivan and Bob Fremont designed the AR15, a scaled-down AR10, they kept the AR10’s carry-handle design, but started with the updated charging handle design. Thus, the AR15 never had a “hook” charging handle." At least one was made with the handle on top. "Another notable change was that Colt decided to purposely change the size and center point of the SP-1’s pivot pin, apparently in an effort to make it difficult to use M16 parts." That is of course correct, but you might add that this change was at the ATF's "request". The first semiauto AR-15 Colt's submitted had the small front hole, but ATF said that was a no go. |
That makes sense, though I'd never heard it explained that way before. Thanks, SC edited to remove some questions that I answered myself with a little mousecraft. |
Even on Oly and DPMS cast receiver guns, I though it was only the lower that was cast. I can't remember ever seeing a cast upper. Do they exist? |
Oly and Hesse have definitely used cast uppers. DPMS doesn't use cast uppers AFAIK, but they do use extruded uppers for their non-standard uppers (Lo-Pro, Hi-Rise, etc.). And while they make the side-walls thicker to compensate for the lower strength, the threaded portion where the barrel nut attaches is still standard thickness (which is fairly thin), and that's the area I worry about. When a cast upper fails, it's usually at the barrel/upper junction. The other problem is if you have a kB!. A forged upper is bad enough, but a cast upper will shatter like a hand grenade into small pieces of shrapnel. <shudder> -Troy |
Wow. Neven knew that! Yet again, Arfcom teaches me, and I've been around for a long time. Thanks Troy! |
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