A new brush will be quite tight in the bore but it sounds as if you are new to cleaning a .22RF. If so, there are some things you should keep in mind. Doing so will retain the accuracy of your .22.
#1- 22 RF guns need to be cleaned rarely. Far more damage is done by over cleaning than by under cleaning.
#2- If you have a aluminum cleaning rod, particularly a jointed one, throw it away and get a brass, steel or coated rod.
#3- Never clean your gun from the muzzle. If you have a gun that can't be cleaned with a rod from the breach, use a pull through. You can easily make one from a length of weed wacker line.
#4- It's rarely necessary to use a brass brush on a .22RF. I do so only if cleaning without one fails to restore accuracy or there is something I can't get out any other way.
#5- It can take several boxes of ammunition through a cleaned bore before accuracy returns to it's best.
Keep in mind that the rifling at the muzzle is the most important part for accuracy. Forcing a new brass brush down the muzzle with an aluminum rod is almost certain to degrade accuracy to some extent.
Hope this helps