It depends on your chamber and the die you are using. It would help if you could give a little more information on what exactly you are using.
If you have a custom chamber that has a tight neck, it is possible, in some instances that you can reseat another bullet without resizing the neck.
This is usually not the case though. The neck must be resized using some kind of die with an expander button or shaft as in the Lee collet dies.
I have a 224 TTH, and I have to resize the neck. If I am not full length resizing, I use a neck sizer for a 22-250 and just resize a portion of the neck.
If you resize the neck without the expander, you will probably be able to seat the bullet, but the neck tension on the bullet will be excessive and will not be consistent, which may lead to poor accuracy, and other issues.
Also. Very important. Check your brass for "doughnuts". I have to ream the inside of the neck where it meets the shoulder to get rid of them. You can find out if you have them by fitting a bullet into a fired case neck. If the bullet easily slides down the neck and then stops when you get to the shoulder junction, you have a "doughnut".
Regarding your question about the TTH. I don't have the actual dimensions of the TTH, so I am not sure, but it looks to me as if the TTH is just a simple neck-down of the 6mm. The shoulder seems to be the same as a 6mm, approximately 26 degrees.
I am impressed with your load. 50 gr. of RL 22 with an 80 gr. bullet has to be smokin'. Shoot that with restraint. I am no where near that with a 75 gr. bullet.
I really like mine. It is one heck of a coyote killer. I just wish I could shoot it more.
Good luck.
Jim