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#10: My Rules, Part One - The Mechanics of XP and Grenades

This article originally appeared in Shannon's column at rpg.net as Fifth Imperium #10 on June 1, 2010, and was reprinted in issue #007 of Freelance Traveller.

For the last year now, I've been running a Traveller campaign using Mongoose's Traveller rules. It's been a monthly affair that's largely set up as a string of one-off adventures to accommodate the somewhat infrequent play. I invite you to read my Actual Play for the game if you happened, which I keep up in (sometimes excruciating) detail.

I'm generally happy with the Mongoose rules. The unified task system works well. It's easy to arbitrate, and ever since I got my Referee's Screen it's been extra easy to set difficulties and move up and down timeframes accordingly.

However, I've never known any GM who was 100% happy with the rule system he was using, and thus I've introduced a few tweaks, the first two of which--experience and grenades--I've written up below. I invite you to use them in your own games, and if you have slight tweaks that you use in your own Mongoose Traveller games, I'd love to hear about them over in the forums.

Character Experience

Experience has always been a bit of a bugaboo for Traveller, ever since the 1977 Classic edition of the game came out without experience rules at all. Mongoose's Traveller instead offers up "training" rules (see Traveller Core Rulebook, page 59)--but having adventurers sitting around starports spending weeks of time just to bump up some skills kills my whole sense of adventure. I'd rather have them, well, travelling.

As a result I've introduced a simple experience system to my Traveller game. Its goals were: to offer constant reward; to offer incremental improvement; and to not throw off the power level of the game as the campaign goes on.

Here's the result:

The Rules. Each active character receives a "tick" at the end of an adventure. This tick may be placed in any skill they rolled during the adventure or in any other skill which they could be reasonably said to have used, whether it was rolled or not.

Conversion. This ticks can later be converted into skill levels. Two ticks can raise an untrained skill to level 0. Otherwise, a skill can be raised to a new level with 4x the level in ticks: e.g., 4 ticks for level 1, 8 for level 2, etc.

High-Level Limits. A character is limited in how many high-level skills he can maintain at a time. This limit is typically one level 4 skill and two level 3 skills. If a player raises a skill up to level 3 or level 4, and thus exceeds this limit, he must simultaneously drop a skill down from that level as well.


I'm generally happy with the Mongoose Traveller combat system. It's sufficiently tactical to keep things interesting, both in moving around a grid and in making combat choices. I think it learned some good things from D&D 3E. However, I found at least one place where it just hadn't been thought through enough: the use of grenades.

The main problem is that though the weaponry exists, the rules for how to use it are unclear. Here's what I do:

The Rules. In order to fire grenades, you use a skill appropriate for the way in which the grenade is fired:

Thrown Grenade: 2d6 + Athletics (co-ordination) + Dexterity DM

Grenade Launcher: 2d6 + Weapon Skill* + Dexterity DM

* For underslung launcher, use the appropriate Gun Combat specialty; for standalone launcher use Heavy Weapons (launcher)

The Traveller rules correctly list blast radii for various grenades, and those should always be considered. However, what they miss is scatter, and that grenade always lands somewhere.

The Scatter Direction. Use 1d6 to determine the direction of scatter. Skip the two directions directly perpendicular to the grenade throw. For example:

(If you want to do this with a 1d8 instead, that might be simpler, but I figured it was better keeping to the only die that Traveller uses.)

The Scatter Range. The grenade scatters to a distance of 1d6* squares. If you want to keep things simple, just roll that as 1d6 in the appropriate direction. However, for a bit more unpredictability, roll that as an "exploding" 1d6, which means you reroll the die and sum up the total if you roll a high number, continuing until you don't get that high number.

For all thrown grenades and grenades fired at short range or less, explode on a "6". For example a "5" would scatter to 5 squares range and a "6" + a "4" would scatter to 10 range.

For medium or long range, explode on a 5-6. For very long or distant range, explode on a 4-6.


That's it for this, the first in my (short) series on rules variants. In future articles I'll talk about my starship combat variant and my narrative variants.

This month, I'd also like to point you to a Traveller article I recently wrote for Mongoose. It's got complete crunchy rules for creating Sword Worlder characters in Mongoose Traveller and can be found in Signs & Portents #80 (which you can download for free).