While bullets have gas escaping around their heel as they exit the muzzle, Sierra Bullets proved back in the late 1950's that hollow point bullets had more uniform heel dimensions and gas escaped most uniform around them. That's why they started hollow pointing their 30 caliber match bullets instead of making FMJBT ones. The benchrest community had known this for years and their hand made 22 and 24 caliber match bullets were hollow pointed as were Sierra's 22 caliber match bullets at the time.
The most common cause of bullets jumping off the bore axis as they leave is their unbalance. The centrifugal force of an unbalanced one spinning around 200,000 rpm to pull it off the muzzle axis is quite a bit for its size. While their outside dimensions may be perfect, the uneven thickness of the jacket an slightly off center lead core or extra tips puts their center of mass off the center of form axis. This is the reason it took bullet makers years to get uniform jacket material to make long and heavy bullets for a given caliber. A friend spun some Lapua match bullets in a collet spun by a Dremel Moto Tool while measuring the current drawn by it. The unbalanced ones drew more current; perfect ones the least. The perfect ones put 10-shot groups from .7 to 1.5 inches at 600 yards, the others inside 10 inches with few in the middle.
Even the most perfectly balanced bullets can be rendered unbalanced by crimping them in case mouths and starting them into the bore while they're very crooked in the case. Uneven rifling twists can also unbalance them in the bore as can leaving too fast from the case and slamming too hard into the rifling. So does sharp/rough edged case mouths scraping off jacket material seating them. Then there's a rough throat caused by uneven erosion that scrapes off jacket material more on one side of the bullet; it's unbalanced before it's all the way into the rifling.
Sierra's heavy 30 caliber HPMK's ruled the long range matches until better copper was available to make 28 and 26 caliber ones. 28 caliber HPMK's suffered first followed by 26 and then 24 caliber HPMK's. It wasn't until 10 to 15 years after the 7mm Rem Mag set a new 1000 yard record at the Nationals until consistent lots of 28 caliber, 168-gr HPMK"s were available. 10 years after that, 26 caliber HPMK's were available that shot as accurate as the 28 and 30 caliber ones.
Sierra's tests in their indoor ranges pretty much proved that all their bullets are stabilized by the time they're 100 yards down range. That aside, if any bullet's fired in a poor barrel, it may not stabilize until further down range then take the trajectory path it's on when it's completely stabilized.
