Hoot,
I don't have experience actually loading this cartridge, but can offer a couple suggestions.The German designation for the Vierling is 5.6x35R, and for the Hornet it is 5.6x36R.I don't know if a mm was added to case length when they thickened the rim,or if the different designations was only to keep them apart.It would be worthwhile to verify case length after thinning the rims.It will be a "trick" to do the thinning yourself.If you thin from the front side,you will have to make a spigot to both hold the case away from the chuck/collet to give room for the cutter,and to avoid crushing the case.You may decide to thin from the back side,which would be easier for the thinning itself,but would require deepening the primer pocket.Lyman makes a primer pocket uniformer which will do this, but in my experience it is easier to turn the case in the lathe rather than try to do it by hand.You should do one and section the case to be sure the "web" is thick enough. It helps that the cartridge should be loaded to lower pressures than the Hornet.The Vierling was loaded to about 2000 fps,and loading it much faster would not only increase pressure, but the rifle wouldn't likely shoot to the sights.There are variations in groove diameter in these rifles.You may need a .222",.223",or .224" bullet,fortunately all three diameters are avaliable(.224" more so).You should "slug" the barrel and/or make a chamber cast to verify the dimensions.What type rifle do you have?
Mike
