Greetings all.

I've been on and off AR15.com since about 1998 before the great meltdown. After a long hiatus I decided to see what has been happening in the world of retro ARs. I picked up a 603 no butt trap stock and pistol grip at Louisville a couple years ago so this was in the back of my mind.

Then my local collectables shop gets in several boxes of gun parts. Contained therein was the following... PERFECT for a 603 retro build.

Unknown, unmarked upper with engraved rear sight markings, MP 12 barrel in almost new condition save for some wrench marks under the NO DRAIN HOLE handguards, straight slip ring, forged machined FSB, a separate undrilled no drain hole FSB, early profile stainless gas tube, A1 port door, CHROME bolt and carrier.



Pay no attention to the 601 pistol grip in there...



So does anyone know the story on the unmarked upper with engraved rear sight markings?



The FSB was installed improperly, so that will be swapped out. Should I go with the drain hole FSB that has already been drilled, or send it out to get the no drain hole one fitted?



Accessories, too.



Just need a Colt gray upper and some small lower parts to make this a nice one.

No, no I said they "fell into my lap". they weren't given to me.

I don't think I got too bad a deal, though. I'm hoping somebody knows something about that sandy-finish black upper. It's got engraved L -> R markings by the rear sight. No other marks.

It was a put-together upper and never fired. The finish inside the upper is still untouched. Probably would not have cycled anyway given how the FSB was installed. I think the holes were drilled with a hand crank drill.

I need to go back and buy the rest of the 601 mag pouches.

Not with a forward assist. That one is a definite anomally since it also doesn't have the recess under the ejection port to match the lower. I'm going to go out on a limb and say that maybe the sight markings were engraved to correct something wrong with a 603 upper. Or maybe a GM/H+R or some other type of replacement upper.

OP - looks like you have a hodge podge of assorted parts there. And a nice assortment at that. I see the beginnings of at least 3-4 new builds.

ETA - what is so nasty about the fsb that is on there? It looks OK from the port side.

That is a strange upper receiver. I'm no expert, but I've never seen a 603 with engraved sight markings. It doesn't look like a Colt, without proof marks, although they may have been lost when it was refinished. If it's a Colt, then it's really strange.

The pins are not correctly installed. Here are some closeups.





I also have a PM upper group with MP C barrel and late FSB. I was going to either turn that into a black A1 or sell parts off and raise money for a 'Nam A1 build with gray receiver.





Needs a little repark on the barrel group, got rusty and somebody buffed it and cold-blued it.

That would be an H&R or GM upper and probably matching barrel. I'm not the expert some of the guys are on these to sub-contractors but one of them will be along shortly to tell you what you have. If you're interested in selling it, please let me know.

I would be inclined to make the pin fit with the FSB that is on there - provided it is correct vintage for the barrel. You can always file a flat or whatever on the pin to make it work. Who knows there might just be a burr somewhere inside the hole or on the pin that is keeping it from reaching the proper depth. Remember, always modify the cheapest/easiest to replace part whenever possible. Pins fit that criteria - retro barrels...not so much.

It will be a crap shoot as to whether or not another already drilled FSB could be fitted without it looking worse than what you have. YMMV

If you can get the pins to work and look decent, it wouldn't be out of the question to grind the flash off of the FSB and have it reparked - contact John Thomas. But before you go that route it wouldn't hurt to check and see if one of the other FSB would match pin holes by chance. Even a FSB without pin holes still may get messed up because you are still going to have some drill walk with the 'holes' that are already in the barrel.

I guess what I am trying to get at is proceed cautiously and methodically and exhaust all options before modifying major parts.

If you want to trade the upper I'm sure there are a bunch of guys here who would be glad to.

As far as all the extra parts you can just send them my way before they infect you with 'the bug'.

Just trying to help out.

This is a darn interesting thread. I had no idea that the engraved sight wheel markings came on anything other than a 602. So, is the conclusion that the only 603s with these engravings were non-colts, or did some of the early colt 603s have engraved sight wheels also??

It's not painted, rough all over inside and out and Lacquer thinner has no effect. Plus, I accidentally scratched a drill bit over it trying to adjust the rear sight and it skipped off like the upper was coated with diamond chips. Not a single mark.



No flash on front but no machine marks. If it was removed, it was done well or ground flat and smooth when refinished black.

Anyone know what the finish is on the upper and where/who refinished them like this? I have a 604 that has this exact finish and i need to strip it or glass bead it whichever will remove it. I do know it is tough as can be.

score. those are pretty hard to find and don't come up often.

Well, I got some more parts... almost enough to finish one rifle.

Got a couple barrel assemblies:



NIW Charging handle



MP C barrel with forged, smooth FSB



C MP B Barrel with early CAST FSB:









LIKE NEW bore



Along with NOS magazine buttons, dimpled pins, slip rings, no-hole butt stock screws, NIW '74 trigger guards, new in box pistol grip from '69, pistol grip screws with the hole through the head. Oddly enough, there were no mag releases in this grouping. I passed on an absolutely new in wrapper C MP CHROME BORE barrel assy. Didn't really need it.

I knew this guy had a bunch of gun parts, but I had no idea the scope and selection. His specialty is WWII stuff, but I guess he dabbles in this for a revenue stream. Said he "hates" AR rifles. There were 2 or 3 chrome carrier keys IN THE WRAP and 5 or 6 full chrome bolt assys. They were in the "for sale" bin, but he wouldn't let loose of those without checking out the state of his collection.

I really don't NEED the barrel with the cast FSB. If it was a M VP barrel I'd keep it, but I don't need a '64 base on a 70's barrel.