PMC carbine, Is it really a commercial Plainfield? What about barrel?

[colreed]

RECEIVER

Recently acquired a carbine simply coded P M C on rear of receiver.
http://i119.photobucket.com/albums/o...ce/pmccopy.jpg

I assume this is for Plainfield Machine Co but can’t confirm with War Baby I, II or Reisch. In fact, fig 729, page 750 states that Plainfields are “blank behind rear sight”. If it is Plainfield, could it be a very early model? It is an investment casting.

Plainfield markings are supposed to be on the front of the receiver per WB II, page 750.
Mine has no marking there.
http://i119.photobucket.com/albums/o...fgcodecopy.jpg

There is a SN on the left front which does agree with WB.
http://i119.photobucket.com/albums/o...20piece/SN.jpg

BARREL

Is very unique. Cannot ID from books. Only marking is on top rear of barrel.
http://i119.photobucket.com/albums/o...fgcodecopy.jpg

Gas cylinder is separate piece with a straight front face but has no pin for removal. Also, the barrel has an added stepdown just fwd of where gas cylinder is attached.
http://i119.photobucket.com/albums/o...gascylcopy.jpg

Muzzle has a flat face but no bevel on outside. Bevel is on the INSIDE.
http://i119.photobucket.com/albums/o...ebevelcopy.jpg

Muzzle wear approx -1.
http://i119.photobucket.com/albums/o...wear-1copy.jpg

Additional barrel info:
18” long.
Appears to be a 2 groove, but grooves are wide.
Has smooth black exterior finish. No rework apparent.
Bore appears chrome lined. Am thinking a type D (WB page 285)
Has short skirt.
One inch behind front sight, dia measures .580. This is .017 less than the .597-.600 std spec.

Could the barrel be a turned down 1903 Springfield mfg by Small Arms Co., Bridgeville, Penn? (WB page 749)

The entire carbine shows practically no wear even on bolt lugs.
It came equipped with an M3 sniper IR scope mount bar with vintage Weaver scope. See CMP Discussion Forum - Unusual find, pictures and some questions

Have posted on the CMP forum as well.

Would appreciate any comments/input regarding this carbine.

Information

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