Hi all,

I recently traded a gentleman for a retro-style stripped upper. I don't want to call it the wrong thing so I'll let you take a stab at ID'ing it:
-"A1" style rear sights
-No shell deflector
-Has a forward assist
-pivot pin hole seems to be .250 on Starboard side, but has a recess on Port.

The problem I have is that the upper wobbles like all get-out when i put it on my modern lower (it's a piecemeal build so it's sharing the "gun" part right now). at first i thought it might be an SP1 upper, but the more i look at it I'm thinking the front pivot pin is the Colt 601 style (which i don't believe had a forward assist)..


it functions using the normal modern pivot pins but I'm not getting any decent groups out of it. Do you guys know of any way to get whatever type of upper this is to mate to a modern lower?

Thanks!

pics are better than descriptions.  lots of pics.  close up, all sides, zoom in on any markings you see.

With f/a it sounds like a run of the mill 603 or 604 upper that happens to still have a rebated front lug.

just took these with my iPad...the markings actually show up clearly...

Please note that i received the upper completely stripped. BCG, FA, barrel etc. were all added by me later, so don't date based on any of that.






http://i294.photobucket.com/albums/mm92/Wild_Huntsman/image1.jpeg


http://i294.photobucket.com/albums/mm92/Wild_Huntsman/image2.jpeg


http://i294.photobucket.com/albums/mm92/Wild_Huntsman/image.jpeg


http://i294.photobucket.com/albums/mm92/Wild_Huntsman/image3.jpeg

XM16E1 square forge upper.  Not the earliest with the recess under the ejection port but still pretty early.  Looks like it has some pitting that was painted over.

Thanks, that makes sense--is there a way to get this to mate up well with a modern lower? or are my only options NDS lowers?

How bad is the wobble?

Sounds like a run-of-the-mill 603 upper.  The rebated lug is a throwback to earlier rifles but works normally with modern pins.

Without seeing it, it's hard to determine how much "wobble" the rifle has or if it's abnormal.  Many (most?) old ARs  have less-than-tight upper-to-lower fit but it's not a critical factor to accuracy.  Remember that your bolt locks into the barrel extension lugs, creating a relatively solid firing platform regardless of whether the upper and lower are "tight" or not.  And with the sights also fixed on that same solid firing platform (unlike, say, an FAL, where the rear sight is on the lower receiver and the front sight is connected by the barrel to the upper receiver), your mechanical accuracy is all in the upper assembly.

I point this out only because you might be disappointed if you tighten up the receiver fit and still not get "decent groups."

Accuracy is going to be more likely limited by the quality of the barrel.  (I assume the retro upper came with a retro barrel.)  
Some old surplus barrels are simply shot out.  Some may have rough bores.  Some may have a damaged crown or flash hider.  Remember, you're not dealing with a factory-fresh barrel.

Plus, you don't say what you mean by "not decent" groups.  Unlike a quality barrel today, which may very well be capable of half-inch groups at 100 yards, even a good condition retro barrel will probably deliver something closer to 3 or 4" groups--and that's assuming that you're doing your part.

Having said all that, if you want a tighter upper-to-lower fit, order a full-fence lower from Nodak Spud.  NDS receivers are purposefully manufactured to fit tighter than most production receivers, the quality is excellent, and it'll look "right" on your 603 upper.

Good luck, and post pics!

ETA:  Sorry--you posted pics while I was typing!  Consider the Nodak partial-fence lower.  It'll look great!

it'll fit any modern lower.  the rebate is for the earliest uppers that didn't have a spring/detent to hold the pivot pin in place.

if there is some wobble that bothers you, you can use an accuwedge by the takedown pin or use an o-ring around the pivot pin.  either of those will tigthen up the upper and lower.

the barrel is actually a new del-ton 20" A2 (1-9) that has been turned down to a1 proportions in front of the FSB. Barrel wear should not be an issue. By the same token the BCG is brand new (R-Guns).

the build was the result of me shooting (and loving) an F/A M16A1 at my range, and wanting a repro (semi only since I live in IL), as well as the fact that my girlfriend wanted a lightweight rifle for the range. it's a spare-parts historical build using what I can afford for now.

As far as accuracy is concerned, I'm getting 1.5-2" groups with my heavy-barreled M4---this is probably in the 5-6" range. The twists are different--maybe I haven't found an ammo it likes yet.

the wobble isn't your normal up-down rattle (accu-wedge fixes that). What bothers me is the side-to side play along with the up and down. I wonder if taking a video of it wobbling would help?

Take out the front pivot pin and check the side to side movement between the receiver lugs of the upper and lower.

I had one that was loose and I was able to find a few perfect fit, ultra thin aluminum washer / spacer.   One between the lugs did the trick and no one would ever notice it .
The washers came from an old bin of electronic parts.  No way I can tell you the size, but a machine shop could make you some if inclined.
You could make one from paper thin Delrin or Nylon sheet as well

Thanks HAL, there is a company online that sells those shims in 10 packs--given the wobble and experienced by me that looks like the most likely culprit (and it's fairly common).

I could probably use DAB beer can aluminum too--that's how I shimmed my Mosin :)


How would I go about "refinishing" the upper if I did get a NoDak lower? some kind of grey? could I go with OD handguards in that case?

The preferred way would be to send it to US Anodizing and have him re-anodize it XM Gray; but I don't know if he is taking orders.  I would google them and call.

Next would be Norells or duracoat.  Someone else can answer about that as I have never sprayed one.

Imarangemaster has posted several times that he's used grey Krylon primer and it's a much tougher finish than he expected. If I were doing a budget build I'd seriously consider it. Cheap to touch up too.

The one issue I have with painted finishes is, they are still painted, and if you are trying for a BTDT wear pattern, very difficult to do compared to anodizing because it just comes off to easily. I learned this to my dismay on a 601 lower I picked up.