A drop in on a 10/22 imo is 90% effective. A cz 455 not so much. Too much variation in shank diameter and distance from receiver face to bolt face recess. A current lilja drop in has a shank OD of .707" and a shank length of 1.191". It uses a Benz chamber. The new lilja drop ins will be done with shims at my recommendation. This will allow you to set the shank length for ideal headspace. They will use what they call the "lilja 2" chamber. A feddersen barrel uses a Benz chamber with a shank length of 1.187". Haven't measured the shank OD but I can later. The 455 receivers can take a shank OD anywhere from .706-.712" which is .006" of variation right there! On headspace most will take a shank length of 1.193"-1.197" for the ideal headspace. Factory barrels are 1.189" with current lilja drop ins at 1.191". This is still way off but what can ya do when the actions vary like this? I'll tell ya, custom fit! Doesn't cost much more to do it and the results are totally worth it. Of course it takes more than just barrel! Bedding, ignition, trigger etc all need to be up for the task.