I picked up a 604 upper a long time ago for like 350 bucks and some spare parts for a complete build.  These parts come from the export M16A1's from the 70's that were released a while back.  I want to make sure I am historically correct now since I looked at the price of parts.

What lower and parts should I use on this build?  One gentleman said I should go partial fence.

The barrel I have dated with the guide as late 67 to 68 or so.  Barrel is marked MP with the C near the muzzle.  Chrome chamber but bore is not chrome.  Early bend gas tube.  A1 flash hider.  Thing looks like its new.  There are hardly any marks on the anodizing and its not been refinished.  I assume this is late XM16E1 (603) and very early M16A1 territory, so it would be correct to use later parts.  I am thinking indeed the barrel is still early enough to use the late XM16E1 configuration lower partial fence lower now.  I was thinking it was late 604 lower (full fence) but I think its late transitional period.  What serial number lot do you guys think this would have came from? 750k to 800k?

I have all shiny furniture for it.  Would that be correct too?

I seen the prices on these parts and my jaw dropped.  I decided I am off to build a A1 clone that I can actually shoot without fear of destroying a piece of history.  Wish I would have snatched up some early XM16E1 parts when I could have.  I would have loved to get a non chrome barrel.  Build a early rifle to do my own testing with.  Validity of the Ichord report and try different powders.

Pictures would be very helpful. Could be Colt, GM or H&R with those markings and timeframe.

Colt upper and barrel

Don't confuse 603s and 604s. They are technically completely different models that were produced concurrently with one another. Ie, if you’re saying you have a 604 upper and want to be historically accurate, the XM16E1 really shouldn’t be a part of the conversation (technically speaking). Of course, we know the rifles are mostly the same, the difference being the bolt forward assist, or lack thereof.

I am Army and therefore tend to pay more attention to Army rifles. That said, generally speaking, 604s are the same. Based on what you’re describing, I would probably go full fence lower, though I think you could probably get away with a partial fence.

As stated, pics would be helpful.

I agree with this.  /\/\/\  But, it also depends on what upper receiver you have.  Is it a "square" or "round" forge type.  A "round" would be for a late 604.  That's what mine is built from. (I had the same barrel as you, but couldn't use it as it came demilled)

Full fence lower for the MP C barrel

I will try to get pics later.

I can't figure out this picture thing.  I have settled on the full fence just like I believe was correct a decade ago.  What are the correct roll marks for a late full fence 604?  Everybody's focus is on the early 604.  Would late be just marked M16?

The photos are off the internet from about five years ago.  They were labeled as an "Unfired AF 604".




It has a full-fence lower.

Thanks

I have a late fully transferable RR Colt M16a1, and the roll mark where it says COLT'S FIREARM DIVISION" is exactly like mine and every other transferable Colt M16a1 I've ever seen.
I suspect the "COLT'S", "FIREARM", and "DIVISION" must be individual words on the machine and not from the same roll.
The word "DIVISION" always seems to be pressed most prominently and "FIREARMS" the lightest.

And that is something I've never seen correctly cloned.


RCA

I don’t think that’s correct, but @aeyoung may be able to chime in and give a better idea ^

To the best of my knowledge that is all one roll.

Roll dies will have differences depending on the machine, operator and position.

These weren’t meant to be perfect collectors pieces

the simplest answer is the correct one, there is alot of variation in roll marks, the forgings are also wider in some spots sometimes which means uneven markings. Thats a late M-16a1 and looks better than most of the real ones i have seen, the early ones are often crooked, markings sometimes so light you cant read them.

Old dies weren't perfect. They would take forever to make if they did one word at a time.

C