71/84 Parts Rifle

[Patrick Chadwick]

I am also totally puzzled. But is this odd hole perhaps underneath the backsight block? If so, fold up or remove the backsight leaf and inspect.
Look for a hole or evidence of a hole having been plugged. You want to be able to look underneath the leaf spring!

There used to be so-called "salute" rifles produced over here, where the barrel was blocked off, and the gas from blank firing vented through a hole, usually hidden within the backsight block, underneath the leaf spring (or rather, where the spring had been). The chamber also had to be altered so that it could not chamber the original ammo, only (typically) 9mm gas cartridges. They don't make them like that any more, as the potential for misuse by removing the blockage in the barrel and fudging up special ammo was all too obvious.

The barrel is, of course, FUBAR for shooting!

Can you manage a couple of pics?