Deeangeo, success. I know I said I was busy for the next few days, however I decide to go in at 5.00 AM this morning and have a go at sorting this feeding problem. Immediately upon removing a small amount form that protruding lift ramp the cartridges started to feed, although with considerable force required. However before touching the lift ramp you could not feed at all. I then continued removing small amounts at a time and continually testing, eventually ending up with a lift ramp that looks the same as Iowa's in his picture. It fed really well but I noticed that the lead nose of the bullet was dragging slightly on the feed ramp which was a little rough. I then polished it to a mirror finish and now it feeds five rounds perfectly.
The question still remains though "Why would it not feed now when it obviously did 100 years ago" considering I am using Norma brass and Woodleigh projectiles, in other words top quality components. The only conclusion that I could come to is that the cartridge cases and projectiles must have had subtle differences to today's brass and with most of the records destroyed it is difficult to determine. It is still strange though that the previous owner of your gun said he had no problems feeding, which means he either had a large supply of original ammo, or he never actually used the gun while he had it, or he is bullshitting.
Anyway, if you shape and polish to copy Iowa's rifle you should find it works perfectly.

Waidmannsheil.