New rifle, franken-AR.

[War Squirrel]

Found this funny looking devil in a gun store over the weekend, picked it up for $400 cash and an old Smith and Wesson. Can anyone tell me what I have here?
It has a pencil barrel marked "FNMI MP CHROME BORE", the FSB is marked "5 R", it has a flat handguard retaining ring, and the buttstock appears to be A1 length, as it is shorter than my friend's A2 stock by about an inch. The flash hider is the old full-birdcage type. The BCG is marked C on the side and the hammer cutaway goes all the way through the rear of the bolt. Upper and lower are just Palmetto State Armory stock.







Was this thing built from old surplus parts? Anything rare on this?

 

[cfullgraf]

There are parts available these days to build a retro A1 version.

 

[highpower]

What you have is a semi-retro AR15-A2, with a few A1 parts thrown in for good measure. The barrel was made by FN (which is very cool) and the rest of it is very likely surplus military parts.

The upper and lower are new, current production parts, The buttstock is a type E (M16-A1) piece, and the barrel profile is, of course, the early pencil style. The handguards/handguard ring are also A1 units.

It is indeed, a true frankenAR. Nevertheless is it is cool as heck. I have a certain fondness for the early AR's and have acquired a few.

Top to botom:
Model 602/AR15
Model 603/M16-E1
Model 741/M16-A2
Model 629/XM177-E2

 

[War Squirrel]

Thanks hipower, I had no idea that it was an FN made barrel! Any significance to the R 5 on the FSB? What would I need to turn it into an A1?

 

[highpower]

Any significance to the R 5 on the FSB? What would I need to turn it into an A1?

R5 is just a casting code. To make it an A1 you will need a upper and lower like the ones on the rifle second from the top. Also a teardrop forward assist.

Like these:

 

[1911 guy]

Yep, franken-rifle. Doesn't have to mean bottom of the barrel, though. The fact that it's a FN barrel bodes well for the overall quality. It's a mish-mash of A1 and A2. I'm not aware of any quality bolts that are cut away completely through the rear of the bolt carrier.

 

[highpower]

I'm not aware of any quality bolts that are cut away completely through the rear of the bolt carrier.

Commercial Colt semi auto bolts from the mid 80's through the mid 90's were cut out all the way in the rear.

 

[1911 guy]

See? I learned something. I assume this was an overkill to ensure that it could not function like an M16 bolt?

 

[highpower]

I assume this was an overkill to ensure that it could not function like an M16 bolt?

Yes, there was a rather ambiguous letter/ruling from the ATF that said something to the effect that any full auto part could be considered constructive intent to manufacture a machine gun. That is one of the reasons that Colt made the semi auto trigger and hammer pins a larger diameter than the full auto versions. They also increased the diameter of the front take down pin so the uppers weren't interchangeable.

All that BS started much earlier than the mid 80's as the bolt carrier in my Colt SP1 is cut back (but not all the way) so that it can't trip the FA disconnector. I am not real sure why they cut it out all the way back later on.