I don't believe ballistics itself is changed. However, there seem to be a few factors involved in this - whether it be real, or just placebo.
* Change in hit sprites
They are much more difficult to see when further away, and their resident time on the FE is also shorter.
Over some distance it is difficult to be sure if you are really landing hits or not, so you are a bit reluctant to fire long bursts as compared to AH1(at least, for me it is).
Also, the shorter resident time on the FE means the hit sprites "spark" and then quickly fade away. In AH1, people use to say "light it up like a Christmas tree" - literally it did look like a Christmas tree because the hit sprites were shown up for too long a time, making it a bit easier to keep track of where your shots land and how.
I've made some comparisons in how large the plane looks on one's FE over distances, but AH1 and AH2 is much same in that sense. Enemy planes looking smaller than it used to, is a placebo - it's actually the hit sprite that is smaller. It seems that in AH1, the pilots reacted to how the large white globs of hit sprites were shown. The less visible the sprites, the less input we get in how we are firing, and thus the sensation of smaller looking planes.
* Change in tracer smoke
Both cannon and MG rounds have changed in tracer smoke effect. While they are still enough to give a general idea of where your shots are flying, it's very different(relatively less informative) from the "grey laserbeam" in AH1.
Ofcourse, experienced pilots already have a sense of how the rounds fly so they actually don't need tracers at all. It is a hinderance for them because the smoke trail is a hinderance rather than help.
However, for exactly that reason, it seems that for the average pilot who needs tracers to show a general bullet path, the tracer smoke actually becomes a huge hinderance if he sprays relentlessly. The longer you pull the trigger, the more numerous the smoky traill, and harder it becomes to aim. On the contrary, the shorter he pulls the trigger, the less rounds in the air, and less chances of hitting the target. Whichever way, it effects gunnery.
* Change in tracer rounds
The size of the tracer round itself, is also smaller over distances. While this doesn't effect people who never relied on tracers, for most average pilots who use tracers it is a big minus effect since over 300~400 yards its harder to see where your rounds are going as compared to AH1.
* Hit sprites no loner visible through plane surfaces
Like Ghosth said, they are not visible through the nose anymore. When firing during maneuvering, you have no idea whether you got the shot in or not if the lead angle was high. You have to fire, turn away, and then see if you hit him or not.
* Change in FM
The subtle changes in the FM effects how a pilot micro-manages his plane. In my case, I've quit using combat trim completely, because the CT seems to react slower to various changes than it used to in AH1. Maybe the average pilot who uses CT, receive some penalty in fine aiming.
Another change is how the stalls develop in AH2. A hard stick pull nearing the edge of envelope, with a sudden rudder input, will put your plane through a 'wobbling' stall rarely ever experienced before in AH1.
Knowing such tendencies, it seems that many people pull less lead than they used to - in AH1, in a stable platform like the Spit for instance, one could very briefly yank the stick with some rudder and force a shot in, and then immediately set stick to neutral to stop stalling. In AH2, that will give you a flat spin.
* Shiny aiming reticles
In AH2, now the aiming reticles react to the light. In the wrong angle, the reticle can be either too bright or too dark.
* Icon distances
The icon distance, is probably the largest effect of them all. Increments of 200 yards. Unless you observe the enemy plane continuously for a certain length of time(usually like 2 seconds..), it is very difficult to perceive the relative difference in speed and distance.
If I watch closely how fast the 'ticks' changed from 800 to 600 to 400.. judging by that I can take a guess whether the target is at 350, 300, or 250.. but ofcourse, this is a guess, and it can go wrong. Wrong guess, wrong aiming. Also, if I didn't have enough time to watch the target plane, insufficient input on how fast the distance/speed is changing.. which also makes it difficult to aim.
........
These are about the factors I could come up with right now. If ballistics itself isn't changed at all, it's quite wonderous how indirect factors can effect gunnery in such ways.
I still can get 400~500 yard shots easily, if the target plane is very predictable and slow - like for instance, when I get within 600~400 tick when the enemy plane is going vertical, I can shoot.
But any other situation, in AH2, now I need to get within 300yards all the time to make sure that I really hit someting and not waste ammo. I also feel much more reluctant in trying a shot that goes over 400 yards. All those things, make up the change in gunnery I guess.
But the change itself, is definately here. While trying out Beta I've gotten out from a lot of situations where I'd never have, were I in AH1. Like, a mistake in maneuvering landed a Spitfire behind my Bf109G-10 between 200~400 range. We were both slow. I actually managed to out-accelerate the Spitfire and escape unscathed, with some gentle jinking.
In AH1, any pilot, even the newest ones, would have shot me down in that situation. The only way out of that situation in AH1, is to somehow force an overshoot, or jink very hard to avoid bullets, because slight jinking will get you killed. Well, apparently it did not get me killed in AH2.
I've also managed to escape from a lot of .50 armed planes at ranges between 400~600, which in AH1, I'd certainly never would have, or lost some precious plane parts.
If they ever decide to remove ammo counters(which I doubt... ).. that'd be like a finishing touch to it all.
