The front rings are very hard to snap in and keep them round, I have done a few and with the last one I drove the shaft end of some drill bits through the ring to get it round enough to get the magazine tube back in - this required supporting the edges of the ring while it was on the barrel, none of this is easy. A friend recently said he got one to snap in with the magazine tube in place, you have to put one side in and then push on the edge of the other side - if I ever have to do another, I will try that. I don't know if one side is shorter than the other or if it doesn't matter which side goes in first.

The screw is a special #5-48 and has to have a head small enough to fully go into the extruded hole for it or it will keep the inner magazine tube from going in. There are places that sell them, it's the same screw as used for the Model's 29, 29-A and 29-B. #5 machine screws are not common, the more standard ones are #5-40 & #5-44, you will not find a #5-48 other than in a gun screw. Fastenal once listed a #5-48 in stainless but they said they were out and it was a special order with a huge minimum, if they even would do it again.