The factory barrel only works well with lead core bullets… That is to say jacketed rounds.
You’ll find that the factory barrel shoots very well, but it also heats up very quickly. As the barrel and action begin to heat up, if the ammunition you’re shooting is on the hot side you will begin to experience heavy bolt lift.
A typical round that shoots very well is the 142 gr SMK running with ~41.5gr H4350 in Hornady brass, with LRPs.
Berger 140 factory ammo is pretty great. Likewise most things you can buy from Spark Munitions will shoot very well. Prime 130s are decent but werent the best.
Unlike my TRG rifles the T3X does not like solid copper bullets; I found that they would group around 18 to 19 inches at 100 yards no matter how hard I tried to work up a load. This is because the factory barrel is inconsistent from one end to the other in so far as the overall rifling: parts of the barrel slightly balloon out and then come back in which is not an issue for a lead-based bullet. However it is an issue if you have solid copper rounds because you get blow by the exhaust gases around the bullet. This is not really a problem for most people and lead rounds don’t have an issue with this at all.
Overall with the right lead core bullets the factory barrel is a tack driver.
I will say that in my experience you do have to clean it a lot more because there will be tooling marks in the lands and grooves on the barrel which you won’t see so much from an aftermarket barrel that cost as much as a rifle did.