Sweetwater: I understand what you are saying and I always agree with both Veral and Lloyd. One of your slugs is a wfn but the other I do not recognize and do not see it in my older Lyman manuals but would ask if that is something like a wadcutter?
I shoot the BBs in 444. I found some slugs are just tough to cycle until you tweak the load length just right. It's a pita but satisfying when it works. Even with factory rounds the bullet just kisses the top of the barrel (chamber) before slipping in.
I mentioned before you may have to seat the slug out a bit. I know that Veral will advise you to seat it to fit the chamber and I advise that, as well as seating for overall cycling length, which means it may be possible to seat it out just a bit and get positive cycling.
I have also had to abandon the use of some slugs as they just will not feed properly but fortuantely there are many, many more that do. You may need to fiddle with the length a bit to get things to 'work'....
I just cycled my 444 a couple of times and noted the lifter raises the nose of the cartridge so that the jacketed slug just 'skins' the top of the chamber - this is with a straight cased cartridge, about the same length as the 356 but I would think that with a necked cartridge the loaded round should slide right in, unless it's too short and I think that would cause it to hang up.
However, how do you cycle your action?? If you are a gentle soul who treats the lever tenderly it may not lever or cycle properly. With mine I have to lever it back positively, and it is a bit of a long throw I might add and also add that on occasion I 'short stroke' it and may hang myself up.... I have found that if I am gentle with the lever and look to see that everything is 'sliding in smoothly', I may often get a hang-up like you describe. Regulation levering is postive.
If you are concerned about deep seating the bullet and raising pressures I would suggest a Lyman factory crimp die - best darn thing inna whole world for levers - and you don't have to worry about crimping in a crimp groove - some of my 444 slugs are loaded ouot beyond the crimp groove but do not move under cycling pressures thanks to the factory crimp die. HTH. Mikey.