Anyone seen this on back of Receiver?

[painter777]

Wondering what this Peen or Dimple could be from or why?
If it has any meaning at all.
Don't believe it has anything to do with the Recoil Plate Fit.

Has anyone ever seen this before?
Could you keep this in mind and keep a eye out next time your tearing a Carbine down to look for this?

Thx

http://www.uscarbinecal30.com/forum/...d_receiver.jpg

[browningautorifle]

Looks like maybe a hardness test, like a rockwell.

[eb in oregon]

Looks like maybe a hardness test, like a rockwell.

Too big, Rockwell testers don't leave that big a dimple. I'd hold for defect or a locating feature but not being able to really see it that is conjecture.

[painter777]

Jim,
I first mentioned maybe a high spot was knocked down that impeded a good Recoil Plate fit, but they shot that down.

Hardness test has been brought up, but no follow up yet. Just such a strange area to test IMO.

I have no idea, never seen or heard of this before. It's being knocked around on the CCCF.
I tossed out a WAG today that maybe the Trigger Housing was stuck and Bubba took a Hammer or Housing pin and knocked it with a Ball Peen to loosen it ??
Using a Pin or Punch to get above the top edge of the Tang.
But IDK

I think it was the owner who stated:
"For reference, it is a SG subcontracted Inland receiver. The dimple is very shallow and perfectly centered."

[browningautorifle]

Hardness test has been brought up, but no follow up yet.

Just because when I was a Platoon Sgt and while examining our rifles, I found my Officer's rifle had a Mounted Police marking and some Rockwell markings, tests. The rifle was an even number so it had been selected, like a number ending in 50. I don't recall seeing it before or since. It was of course the FN C1 A1 rifles, way back early '80's.

[jond41403]

I thought maybe since it was a subcontracted part, when SG got a hold of it, maybe they tested it to make sure their subcontractors were hardening it properly. It is awfully big for a hardness test though

[eb in oregon]

I thought maybe since it was a subcontracted part, when SG got a hold of it, maybe they tested it to make sure their subcontractors were hardening it properly. It is awfully big for a hardness test though

They would test it up at the front of the receiver around the chamber area, the back heel means zip. And again that is not a dimple from a hardness tester. To big, way to deep. And not a ball peen. No way. If anything I've ever seen it looks like a 5/32 ball mill. To perfect for a defect and no ball peen in the world can peen that deep or that small. Nor a punch.

[browningautorifle]

They would test it up at the front of the receiver around the chamber area, the back heel means zip. And again that is not a dimple from a hardness tester. To big, way to deep.

I suppose, the ones on the FN were the typical punch type marking. They were in obvious stress areas.

[W5USMC]

To big, way to deep

I think it was the owner who stated:
"For reference, it is a SG subcontracted Inland receiver. The dimple is very shallow and perfectly centered."

[eb in oregon]

I think it was the owner who stated:
"For reference, it is a SG subcontracted Inland receiver. The dimple is very shallow and perfectly centered."

"Shallow" is subjective. Viewing the picture the "dimple" appears about as deep as large in diameter. No punch or ball peen strike can physically do that. Both tools displace material around the strike. A ball mill will, but it cuts and there is no indication of material displacement around that dimple. Merely the opinion of a guy that spent 25 plus years working with and machining metal.