I recently took a chamber casting of a Winchester low wall rifle. The bore measures .309. The rim diameter is .550 with a .067 thickness. Directly above the rim the case diameter is .419 and it tapers to .354 with what appears to be a very short neck at .342. Near as I can tell there is no throat to speak of. I’ve never seen a camber like this and wonder if it is anything at all. Any assistance would be greatly appreciated. Thanks!