This has been on the list a while. It was sparked off by a discussion on weapons in 40K at an old Outside the Box, but could work for all kinds of games using dice to resolve success and failure.

The starting point was the fact 40K is nearly 27 years old now, in which time a lot of the core weapons have been sculpted in various forms. Compare the original lasgun for the Imperial Guard - or Army as it was - and the Squats, cult etc. to more recent versions. In the real world, reflected in historical and modern wargaming, various modifications and variants also exist, and the same could well be true for other more fantastical settings.

Think about all the possible forms that slings, bows, crossbows etc. can or could take, let alone the range of melee weapons. This is true also for many if not all technologies in conventional science fiction, science fantasy and fantasy, possibly even innate abilities.

Relatively minor differences in operation generally aren't represented in larger-scale games, not least because using standard methods like modifiers or straight rerolls it could be impractical, especially when using dice with a low number of faces, like the d6: the various patterns, marks and mods could then end up more like new weapon types.

The squearoll idea

The key mechanism for managing it is what might be called the squearoll, a kind of reroll that represents tight squeaks, moments the players might squeal. A squearoll is used when the result is on a knife-edge, specifically when one point away from success, with the reroll giving a fixed 50% chance of success and 50% of failure, e.g. a squearoll in 40K would presumably use 1d6, with a result of 1-3 then being failure, and 4-6 success.

Here's an example for 40K. Ten shots are fired using slimline bolt guns with advanced  feeds, represented by Lighter Casing and Faster Action (see below). Each usually has a 3+ to hit, and the results rolled are 1, 2, 2, 2, 3, 3, 4, 5, 6, 6, i.e. six hits. But because of the Faster Action, the 2s can be squearolled. Three dice are rolled, each needing 4+ for success: the results are 2, 3, 4, meaning one extra success, i.e. seven hits in total.

Using this in games

The players agree how many units or individuals in each group have a variant weapon, or how many are assumed to be. Each variant weapon is identical to its normal form but with one or more positive attributes and one or more negative, as agreed by the players.

Possible attributes - rifle-like weapons

Here are some examples for rifle-like weapons, focusing on the 40K ranges especially.
 
  • Longer Barrel, Sight or Stand  / Shorter Barrel or Hanging Trophy
This weapon has a basic range 10% longer / shorter, rounding up / down.
  • Faster Action or Larger Clip etc.  /  Slower Action or Smaller Clip etc.
Each one-point miss / hit with this weapon may / must be squearolled.
  • Heavier Casing or Gun Shield  /  Lighter Casing or Exposed Workings
Each save or similar roll based on armour or physical resilience failed / passed on behalf of the bearer by one point may / must be squearolled.
  • Larger Stock or Bayonet etc.  /  Smaller Stock or Rounded Casing
Each one-point melee miss / hit by the bearer may / must be squearolled.

It's simple and quick once you get the hang of it, and it's WYSIWIG with miniatures. The squearoll idea has a lot of potential uses, maybe for a large part of a given system. It's one way to get a larger range of results without using a larger die size or rewriting stats.
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