PK.

In a GI spec receiver, rivets should protrude .140 from the top of the receiver before installing the sight.

It is likely that your receiver is threaded. Remove the pop rivets with an easy-out, Re-tap the holes to clean them up, a forming vs cutting tap is recommended. The thread size is M4x.7mm. The sight will be counter sunk 82 degrees (American), you should re-cut it to 90 degree to match the heads of the metric screws. When installed with good Locktite, this will stay together well. If you want rivets, you will need to get a GI sight (they aren't countersunk) and re-machine the holes in the receiver. Let me know if you need any help.

Thanks for asking MN Shooter; I'm still kicking, but not as high as I used to. I have not fully retired but don't do the full refurbishes I used to. sse: I have a couple of the threaded ring sights in stock, email me: p-k at myctl dot net Best wishes to everyone 🙂

As i recall, the GI Manual says to replace the spring at 10 1/4" or shorter, or if it's kinked.

When reassembling, retract the bolt 30%-50% and then insert the spring and pilot, allowing the bolt to move forward with them as they fill the gap that would normally allow the spring to escape.

It maybe a cast WH 1928 that was machined to 21; I've seen that a time or two.

Clearly, a modified military part; there would be no need to do something like this to fit a WH (or any other SMG). Someone may have cut the top to try to fit into a semi gun. When they changed their mind the plate was added back on to restore to normal SMG configuration. ????? I don't think this part has anything connection to original manufacture

Tom, look at the lack of radius at the junction of the top flat and the knob; this is usually only found on early actuators IIRC and is not an easy set-up to machine for a fake. The other aspects of this part are like those I've seen previously, including the porosity from the gas welding.

21/28 pilot $50 21 recoil spring $15 28 buffer disc $7.50 Shipping is dependent on order, please email.

The GI tech manual has a minimum length for used springs, IIRC it is 10.25" (someone please check) and no kinks. Wolf makes a great '28/M1 recoil spring, and you don't have to worry about where it came from.

The Early AO drawing notes the following, with an arrow pointing to teh bottom below the retaining lug "Bend grip here before heat treating to throw forward end up .10" to insure firm seating against barrel" In my opinion, based upon observation, all Colt made parts had the bend, as did parts in all 1928 guns. I think the bend in the milled parts was likely eliminated with the M1, and the subsequent multi part assembled grips mounts did not have the bend.

How thick is the top of your receiver?

I have pilots, springs and buffer discs in stock

I can help, email me. p dash k at q dot com

I have seen guns in this condition fire when the magazine was removed; I think Got Uzi has it right.