Pulp adventures is MADE for games set in mid 19th century and turn of the century settings. You will find many useful rules, from professions and cultures to talents and gear plus list of equipment and weapons proper for the age you have selected.
I have used Firearms Law quite a bit. Very nice, and if the ME tables used are kept below 12, with more typical being ME 3-8, a suitable deadlyness balances with playability.
With semi auto weapons, players will be able to fire multiple shots a round and at multiple targets. For example, three single shots at 40%, 30% and 30%, or two singles at 50% and 50%, etc. Full auto, double taps, supression fire and aimed burst can amp up damage and options. I have NOT had any problems using the standard shot options in the Firearms book, but you may want to create a small table showing what shot options are available with activity requirements and the like, copy it and make it into a hand out, unless you have several copies of Firearms Law. This will speed combat up nicely.
This should be obvious, but...GUNS ARE DANGEROUS. Players need to take cover, or they WILL get hurt, bad. The Balistic Puncture crit Table is nasty, but nothing compared to the Balistic Shrapnel Crit Table, which on an 01-05 on an E will destroy a hand and make it useless until skilled surgery can be performed on it. As players learn the ins and outs of firearms crits, they WILL respond by trying to put as many bullets in a foe as fast as they can, uping crits from balistic punture to shrapnel.
I added one house rule the book doesn't cover; listed dameage on the tables is 1/2 damage for single shots and listed damage for any form of auto fire.
Shotguns are horribly dangerous with shot at close range. Seems obvious, but just wait till you shoot a PC with a high SG and get a good roll...splat.
I have ran semi mystical games too, and shamans can hand out neat charms and the like, or PC's can recieve blessings, etc. A charm that subtracts 20 hits from all blows and burns out after 100 hits can be captured from a foe, handed out by a shaman, etc. There are lots of small, neat little things you can add to the game. Keep them secret, and make sure they have a limited life span, or need some sort of recharging the player iknows nothing about.
A few optional rules I have used for special creatures; ignoring all hits from attack tables and only sufferiing hits delivered from crits. Fate or luck points. A creature only hurt by "living" weapons, i.e. hands or wood, etc. I remember after telling Scott his first blast from his shotgun did nothing but the second one that blasted the door frame sent splinters flying that ripped open gashes on the monsters face started a race for the table legs! Have fun with it, and DO throw in the unexspected.
To keep things really simple, I use generic skills in the weapon catagories rather than individual weapons. So one hand edge has small and large blades for skills, one hand projectile has muskets, revolvers and clip pistols, etc. This will free up dev for the much heavier load of skills players will want/need in a modern setting, and keeps things simple.
lynn