Greetings and Salutations. Hmm ... interesting question. I've always played it with the belief of Critical Strikes apply to ranged combat without question. With that said, I did try to look at this objectively. Let's see what the book says on the matter. For simplicity, all references will be from Rifts: Ultimate Edition, the newest rule book in print.
There is the "Natural Twenty" description on 278, but I won't post that here because one of the others addresses this better.
Rifts: Ultimate Edition; Page 344; Combat Terms & Moves wrote:Critical Strike damage can be inflicted with bare hands or with a weapon.
Now it states "a weapon" with no specification if that's ranged, melee, or both. Being left general, we can guess both, but that's only a guess.
Rifts: Ultimate Edition; Page 361; Weapon Modifiers wrote:Rolling a Natural Twenty to Strike always hits its target and does double damage (Critical Strike).
Now, this one is far more interesting since it's in the Ranged Combat section. It specifies a Natural 20, which could indicate that ONLY a Natural 20 will do this. Yet, it also mentions that a Natural 20 is a Critical Strike, and the Hand to Hand provides an increased Critical Strike range. The "Natural Twenty" description in "Combat Moves & Terms" also mentions it being a Critical Strike and gun combat, so that doesn't really help.
On page 363 with the Missile Combat it mentions a Natural Twenty again and doing double damage, but no reference to "Critical Strikes" at all.
So, if you want to know the
affects of Critical Strikes (doing double damage) being the same, then yes, they are the same with Ranged Weapons.
If you're asking if the increased Hand to Hand Critical Strike range (e.g. Critical Strike on an unmodified roll of 18, 19, or 20) applies to Ranged Combat, that isn't as clear. Now the Ranged Combat section and Missile Combat section ONLY mention a Natural Twenty, so one school of thought would be that Critical Strike range for ranged weapons cannot increase.
On the other hand, both references also go into how a Natural Twenty always hits. Also,
all characters have the Natural Twenty Critical Strike. Not all characters have the Hand to Hand increase, so the Natural Twenty reference is the most applicable. So they weren't discluding Critical Strikes (which say can be performed with a weapon), just didn't give it a special listing.
Personal conclusion: By the book as written, the Hand to Hand Critical Strike range is only for melee combat. That's the same as the "+3 to parry/dodge" and the "+2 to strike" only apply to melee/hand to hand combat unless specifically stated otherwise (see Hand to Hand Assassin). Only a Natural Twenty applies to ranged combat.
Of course, I'll still play as Critical Strike ranges applying to ranged combat. Actually, I hadn't ever given it much thought before, but I've also always played Critical Strikes as being undefendable except by another Critical Roll (as determined by a Nat 20 or Hand to Hand table). Basically letting the Hand to Hand Critical Strike act as an extended Natural 20 for more experienced/deadly characters. As I'm looking at it more now, I'm thinking about how wrong (by the rules) that's always been. Not sure where I got that idea from, but the way I always played it. I hadn't really realized just how much of a house rule that was until today.
Not sure how much any of that helped. Hopefully it helped at least a little. Anyways, thank you for your time and patience, please have a nice day. Farewell and safe journeys for now.