This one inspired by this video. Seriously, go watch it. Very interesting. It tests both representative car panels, helmets, and bulletproof vests of the 1920s & 1930s against common pistol cartridges of the day.

The video tests analogs for car bodies of the era, as well as three types of vests.

Spooner Vest

Wisbroad Vest

Dunrite Vest

But how are these devices represented in Gang Busters? Well, the rules include rules for bulletproof cars. But, they do not appear to include rules for bulletproof vests.

To summarize the video results:

While the testing didn’t cover all permutations, it fairly persuasively showed that the vests were effective against the common pistol rounds of the era. In game terms, I suggest using the expert hit location rules and consider the vests to protect the chest and abdomen. Hits of pistol rounds in these locations, are then converted to bruising damage rather than wounds. Note, instead of the normal punching 5% wounds, use the equipment specific values below. Consider the vests as no protection versus rifles and shotguns.

For helmet equipped characters, treat as above, but also treat only fifty percent of head hits as protected by the helmet. Note the helmet material tested was a Vietnam era helmet, but essentially the same was WW2 helmet introduced in 1941. Through the period of Gang Busters, surplus World War I era helmets were available, but their effectiveness was not tested, so I’ve dramatically limited the effectiveness.

As discussed in the video some common rounds may be rated as “metal penetrating”. Treat these rounds are costing twice as much as normal ammunition, and they may be difficult to find or only available to law enforcement agents. Against vests treat as above, but the chance of being actual wound, is now doubled.

They also tested more powerful rounds like .357 Magnum and .30 Mauser. .357 Magnum will only be available after 1934, and likely rare to find. For penetration, treat both as penetrating double what is listed in the rules. First model .357 Magnum was the Smith & Wesson Model 27. The C96 Mauser pistol available (though rare) throughout the period was .30 Mauser. For both cartridge (pistol) type characters with vests as unarmored.

S&W Model 27 .357 Magnum

C96 Mauser

As to the cars? Review of the car rules seems adequate for game purposes. Optionally, for metal penetrating rounds, .357 Magnum, & .30 Mauser, as well as rifle & shotgun rounds, reroll body hits and if a window hit is indicated treat one passenger as hit, ignore other results on this second roll.