Here is my suggestion. For sure, clean the barrel liner. I would NOT suggest polishing it at this point. I ended up doing a very light polish on mine (.177, 600mm) as it would loose accuracy after about 150-200 shots. The light polish helped a little bit but I wont polish more unless I can get a spare liner. On the flip side, many say they NEVER clean the liner and shoot thousands of shots without having to clean. Time will tell.
With a little luck, your M3 may come with enough air to shoot a bit. Mine did. Just make sure the tank pressure is higher than the regulator(s) pressure. The instructions say not to fire if it is not.
If you like to tinker, I'd shoot without the liner for a bit to see how things operate before installing it. Maybe your M3 will be spooky accurate out of the box and you wont need to deal with the liner. Down the road, if you install it you can index your liner and put on the CF sleeve. then report back on the forum what you found!!
As Westwind suggested, if you take off the shroud to either look at what is in there or install the CF sleeve, why not take off the liner, spray the inside with ballistol and let that soak in. Then pull through your patches.
If you did not any air in your cylinder to shoot and your waiting for your air compressor and want to play with your M3, then maybe take the time to do the following:
- The barrel/shroud/liner are all straigtforward to remove and putting them back together is easy and has maintained accuracy for me. If you have any specific questions post or PM me directly
- is super easy to label the valve knob for your own reference to tune and or to share your tunes. https://www.airgunnation.com/topic/your-m3-tunes-here/page/4/#post-1106066
- if you have a FX radar and want to build one of these it can be a fun project . Here is a pic of one I built and I got all the parts from amazon, Shoot me a PM if you want those parts.
Have fun with your new toy!!!