View Full Version : Vertical line on upper receiver
This may seem silly to some but my curiosity is killing me. On the left side of all cast and forged uppers ( that I have seen )there is an embossment that coincides with the recess were the cam pin is when the BCG is closed. On that embossment on the outside of the receiver there is a .250 vertical line. Does anyone know the purpose or meaning of this line. I cant seem to find an answer with the search function. And like I said its just bugging the dog crap out of me. Everything else on this gun has function and meaning....except this little line. I'm getting close to losing sleep on this one. I sometimes will fixate and obsess over something like this. Right now it's just fixation. Please help me !
Thanks in advance.
Vince
organdonor
07-14-10, 23:43
Doubt it serves much of a purpose. My guess is some sort of mark left by the forging process.
arizonaranchman
07-15-10, 01:06
Hmmm, interesting question. Not one I've thought to ask, but curious now myself! But I'd guess at this point in looking at it that it's perhaps something to do with the the casting process with that area?
Ridge_Runner_5
07-15-10, 01:12
My guess is some sort of alignment point for the machinery...
I barely noticed this in the past but now cant stop thinking about it. Thanks a lot! :jester:
My bet is with Ridge_Runner_5's guess. It may be a reference point to ensure consistent proper location of the cam pin slot inside the upper.
Hmmm, interesting question. Not one I've thought to ask, but curious now myself! But I'd guess at this point in looking at it that it's perhaps something to do with the the casting process with that area?
not part of any casting process- they're forged.
i suspect the comment about it being an index mark might be getting warm.. perhaps that little notch slips into the part holder when it goes into the CNC, to ensure the receiver is lined up right. a cutting tool has no idea if it's cutting where it should be- being off by a thousandth can scrap the whole piece.
totally guessing, though.
organdonor
07-15-10, 22:03
Pretty sure LaRue's billet uppers don't have the vertical line. This tells me it's something to do with the forging process.
Pretty sure LaRue's billet uppers don't have the vertical line. This tells me it's something to do with the forging process.
aren't larue's billet uppers billet? no forging process with billet- the term "billet" actually refers to the billet, or solid block, of aluminum that the uppers are entirely machined from.
organdonor
07-15-10, 22:39
aren't larue's billet uppers billet? no forging process with billet- the term "billet" actually refers to the billet, or solid block, of aluminum that the uppers are entirely machined from.Yeah I know. Vertical lines on forged uppers but no vertical lines on billet uppers tells me it has something to do with the forging process.
Yeah I know. Vertical lines on forged uppers but no vertical lines on billet uppers tells me it has something to do with the forging process.
ack.. i misread your post. my bad.
While the reference point ( datum )for machining seems plausible, I don't think that is what it is for. A datum would be a point ( Vertex ) not a line. the inside corner at the pistol grip attachment point would be a great datum point. The notion that it may be an index point or tab for a machining fixture doesn't seem right either, the mark is too small to be precisely placed into a notch and not close enough to an edge to be accurately lined up with a corresponding mark on a fixture. And as for a casting mark, why would that particular casting mark be left on the piece when great care is taken to remove all of the others? And why would that mark be left on ALL of the uppers that are made no matter who they are made by? :confused:
Vince
organdonor
07-17-10, 11:41
I'm gonna call around to a few forges Monday if we haven't gotten an answer yet.
it's a reference mark for the M203 Quadrent Sight.
organdonor
07-17-10, 11:57
it's a reference mark for the M203 Quadrent Sight.This?
http://www.armystudyguide.com/images2/20060626-004.gif
How is the reference mark used?
This?
http://www.armystudyguide.com/images2/20060626-004.gif
How is the reference mark used?
If the range quadrant (angular scale) on the sighting system moves up and down I would tend to go with this answer. However, looking at the above illustration, it appears to me that the sight arm travels up and down along the range quadrant. Which stands to reason considering the high launch angles used to launch a granade. If on the other hand it is used in order to consistently line up the bottom line on the quadrant so that sighting remains the same from gun to gun.....that would make some sense.
Vince
I just found this picture. Based on this picture it would be difficult to associate the mark on the receiver with the range quadrant on the m203 grenade sighting system.
http://i278.photobucket.com/albums/kk103/EW1066/quadrant.jpg
Vince
I honestly never wondered what it was for, but now I'm curious?
MisterWilson
07-19-10, 09:29
Okay, I contacted the oracle, this is what the had to say...
Colt used this vertical line, along with a "+" seen on early lowers (SP1, M1601), as a visual aligning mark used in the manufacturing process.
While keeping in mind that this was all done using 50's era machining processes, the machinist would align the mark in a small viewing area before securing the receiver forging and cutting away.
http://imageevent.com/willyp/firearmsalbums/uscoltarmalitem16ar15556/coltmodel601airforcearmy?p=4&w=4&c=3&n=0&m=-1&s=0&y=0&z=9&l=0
organdonor
07-19-10, 09:52
So it serves no purpose today
MisterWilson
07-19-10, 09:54
Probably not.
Nostalgia?
organdonor
07-19-10, 10:37
I wonder why the line stayed while the x didn't.
4thPointOfContact
07-19-10, 11:12
Dunno... but perhaps the X was engraved (a separate step easily eliminated) and the vertical line was built into the forging?
Just hazarding a guess.
Still doesn't explain why the vertical line has existed for so much longer as I'm pretty sure the original parts for forging have worn out.
So what you"re saying is that the these guns have an appendix. It served a purpose at one time but now it's just there waiting to be removed....
Vince
MisterWilson
07-19-10, 12:45
Consider for a moment the financial cost of removing that vertical line from all the engineering drawings, prints, forging dies, etc.
It was probably forgotten or deemed inconsequential.
By the same token, consider how many times over the last 50 years those drawings have been redone and or changed. Not to mention the fact that these "drawings" started out on paper and are now digitized. I would think that some point along the line some draftsman would have asked......"What is this line for and why am I drawing it" I do some computer modeling for a machine shop and I question "dumb stuff" in drawings. It has saved me, and the machinist, time in the long run.
Not to cast doubt on what the Oracle has said but something isn't quite right. I can understand the "+" being used for alignment because it will give you 2 planes of reference to better align in both the x and y axis. But a single line only gives a single plane of alignment. If the scope on your rifle only had one line how precise would your shooting be?
Vince
MisterWilson
07-19-10, 13:16
Perhaps it's a fraction that holds all of the history & knowledge of the known universe in numeric form.
Any one else care to chime in with alternative explanations? I tend to believe the "relic of the past" explanation, but it still has some questionable aspects. What I'm looking for is a definitive source. Documentation would be ideal. Hearing from the ORACLE was good, but the world/internet is full of ORACLES (no offense to ORACLES intended).
Thanks again
Vince
I designed machinery for 15 years, and many of the older items are still on Velum. I wouldn't doubt that Colt has never bothered to put the old uppers into a modern CAD system....it hasn't changed in decades, so why spend the money. Same with the dies...unless you could save a ton of money, it would cost more to revise the dies than it would be worth (even when replacing them)...the die makers would have to update all their stuff, change processes, etc.
organdonor
07-21-10, 13:18
The Colt customer service guy I spoke with had no clue. Tried to hunt down a guy he said was more knowledgeable than himself. The other guy wasn't around so he gave me the number to a company called Specialized Armament and said maybe they could help. I'll call them later and if they have no answer - I doubt that they will - I'll try calling around to a few forges.
Edit: The guy at Spec. Arm. could only offer a guess. He thinks that the 50's era machining process answer is a stretch and that it is a remnant of the forging process.
Called Cerro but apparently I could only get information about fusible alloys or brass forgings. A company in england, Bolton?, manages their aluminum forging now? This is what I understood from our conversation.
Called Cardinal but, unless you know the name of a person you're wanting to talk to, their automated answering system prevents getting through.
Called Alcoa but the person the operator forwarded me to was out of office.
If MisterWilson's answer is correct then my question is why didn't the mark on the lower receiver persist over the years? I've never seen a forged lower receiver with a mark like that on it. I don't know very much about the forging process. Forges like Cerro, Alcoa, Cardinal all use their own set of dies, right? What about forged lowers?
I would like to add something else to the "forging/casting mark" debate. The dies have to have had changes and redesigns over the years when you consider the transition from the old A1 to the A2 to the flat top uppers. There have been ample opportunities to remove the mark from the dies.
Vince
Heavy Metal
07-21-10, 21:51
Dies dude, forging dies.
Iraq Ninja
07-21-10, 23:26
At least this vertical line made it to the cover of the Rolling Stone recently...
http://images.starpulse.com/news/bloggers/8/blog_images/lady-gaga-3.jpg
Dies dude, forging dies.
The funny thing is; is that's how I spelled it at first and I went back and changed it.
Eye nevur wuz reel gud at spellin stuf.....:D
Dunno... but perhaps the X was engraved (a separate step easily eliminated) and the vertical line was built into the forging?
Just hazarding a guess.
Still doesn't explain why the vertical line has existed for so much longer as I'm pretty sure the original parts for forging have worn out.
It was a raised +, not an X. Here are some pics from Retro Black Rifle:
601 (602s had them as well)
http://98.196.65.94/retroblackrifle/sitebuilder/images/601-Right-601x438.jpg
early 603/XM16E1
http://98.196.65.94/retroblackrifle/sitebuilder/images/XM16E1-Right-409x291.jpg
Dustin
Perhaps and im just guessing that this line was OK'd when put into original production in the designs and over the years was never taken out when changes to the recievers to A1, A2, M4 etc has happened.
Does anyone else have an idea or is this issue a dead end? Will I just have to get over it?
Vince :confused: :blink:
Does anyone else have an idea or is this issue a dead end? Will I just have to get over it?
Vince :confused: :blink:
probably.. i've never seen anyone milk a completely inconsequential topic so thoroughly- i really think you've done all you can do, and will just have to let this one go. ;)
Milking? Wow! Way to dump on some ones curiosity. Well I guess I'm done "milking".
Thanks to everyone who had something positive to add to the discussion.
Vince
Quiet-Matt
07-26-10, 04:53
Well, I was curious. I guess we will never know.:secret:
Milking? Wow! Way to dump on some ones curiosity. Well I guess I'm done "milking".
Thanks to everyone who had something positive to add to the discussion.
Vince
good luck in your quest for 200 posts :jester:
;)
NCPatrolAR
07-26-10, 09:18
Do I need to explain why this is getting closed?
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