Given that there's precedent for a bullet being blocked, I'll do a back-of-the-envelope calculation (on the back of a forum thread?).
A typical bullet travels anywhere from about 300 m/s (subsonic ammo) to about 1,000 m/s (random sniper weapon:
Barrett M82, muzzle velocity 853 m/s). Even with improved materials in the 2070s, it wouldn't be practical for a bullet to be propelled faster than about Mach 6 (2,000 m/s) because of hypersonic effects. So let's use that 2,000 m/s as an upper limit of bullet speed. (Aside from the Thunderstruck Gauss Rifle, which probably is uniquely designed to propel a thin projectile at hypersonic speed.)
Then, consider a Force 4 Detect In-Flight Bullet spell (or some such, to differentiate the fired bullet from those in some undercover cop's (or ganger's) unslotted magazine). Assuming a Magic of 5, that spell has a detection range of Force x Magic, or 20 meters. That's a response time of (20 m) / (2,000 m/s) = 0.01 s, or 10 milliseconds (at most, and that's from the time the bullet is detected to the time the triggered Armor spell is up and running). So that's one current benchmark for "immediate" in the anchoring rules. Another benchmark can be calculated by assuming that, instead of an Armor spell, the triggered spell is a Force 5 Physical Barrier which has a radius of Force meters, or 5 meters. This cuts the detection slack down to 15 meters (if the bullet travels more than that during the triggering, it's inside the barrier), so the response time is cut to (15 m) / (2,000 m/s) = 0.0075 s, or 7.5 milliseconds.
Now, between response time = 0 and response time = 7.5 ms, we don't really have a RAW (other than "immediate"). Then the questions become: (1) Are the Ares laser weapons pulsed? (2a) If so, how long is the pulse? (2b) If not, how long does the spot have to remain on target to cause damage? (3) Is either of these times longer than the response time of the anchored spell? (Or what is the response time of the anchored spell?)
I don't have a good answer for these, except to point out that astral movement uses the "speed of thought" (SR4A, 192). The speed of thought might get you down to a sub-millisecond response time (barely). It's much slower than the speed of light but may still be fast enough to intercept part of a laser pulse. The speed of thought might place a lower limit on the response time of the anchoring, but what's the relevant laser time? Laser pulse lengths can be anywhere across this argument, even down to the femtosecond (1e-15 second) scale. (There are laboratory-sized femtosecond-pulse lasers in the present day.) As a WAG, I'd say the typical pulse length for a 2070s laser weapon is something in the microsecond to nanosecond range, which would still be faster than the best likely response time for the anchored spell.
