Okay, my two nuyen worth here.
First, the lists of weapon choices posted above is a really good start. Likewise, the Ruger Thunderbolt was listed as being specifically developed for Lone Star personnel as their main sidearm, so that would likely be standard issue. Also because the Ares Predator is so tightly connected to Ares (no duh), which owns their biggest rival company, Knight Errant, so the Thunderbolt is a way of being visually distinct from any associations there.
Armour as was stated above should be full SWAT gear, as that's superior to even full body armour. Also consider that Lone Star, being the trigger - happy guys they are, would probably go in ready for whatever scenario earned an HTR visit, be it a heavily armed gang, shadowrunners, etc. So that means they might start with regular ammo, but you can be damn sure they'd carry extra clips of EX-explosive, ADPS, gel rounds, whatever they felt they needed for that task.
Someone mentioned the old 2E Lone Star book, and I really can't agree with that enough. It is absolutely worth a read/browse, because it gives great insight into general law enforcement, as well as obviously Lone Star. Things like how Lone Star personnel are issued a Thunderbolt as their regulation sidearm, but they are 100% allowed to register, train with, and carry their own sidearm instead (hence why some cowboy - enthusiast Lone Star cops might be seen with a Cavalier Deputy instead, which is frighteningly powerful).
Also, Lone Star has 2 separate units that could be considered HTR, depending on the situation. There's the SWAT unit, which is very tactically minded and tries to actively prevent any civilian casualties/damage. Basically modern SWAT, same stuff. They are the scalpel to the hammer that is the second group, Lone Star's Fast Response Team (FTR). The FTR team is there to cause as much damage as possible and screw anyone who gets caught in the way. They are military - equipped and more than capable of dealing with most high-danger threats, as I believe the standard FTR unit is a 12 person team that arrives in a heavily armed and armored Mobmaster(according to the book).
Anyways, that's gear and mentality. One thing the players would have to get over and deal with in the transition from HTR guys to Shadowrunners is the lack of gear available. Yes, they can now tailor their gear to whatever style of runner they want to be, which is great. But they'd have to get used to the fact that finding specialty gear, weaponry, grenades, combat drugs, even electronic equipment (like surveillance gear, tac-nets, secure commlinks, black IC, etc) would be pretty hard to come by without dedicated, reliable sources. Back working for the Star, everything was provided often in relative abundance, but as runners they might have long dry spells for even some types of ammo if a source gets pinched. Big change to have to adapt to.
Anyways, that was a huge info dump for 2 nuyen, but there it is.
