A successful 3 round burst

[Rupert]

Originally Posted by Ulzgoroth

Range, target dimension and motion, and what types of round you are mixing. (For instance, you'll have a lot more of a problem if you're simultaneously firing the high and low velocity cannons of some WWII German fighters than if you're firing a LMG with a standard tracer mix.)

The classic example of this was the MiG-15 in the Korean War. I had a couple of high velocity 23mm cannons and a low velocity 37mm cannon. In its intended role as a bomber-killer this would have been fine as it would've been firing at a reasonably consistent range and not manoeuvring hard. However in Korea there was a lot of fighter-fighter dogfighting and the high-G manoeuvres and engagements ranges that weren't what the guns had been adjusted for meant that it wasn't unknown for an enemy fighter to have 23mm rounds zipping by under it while 37mm rounds went by over it.

[Anthony]

Originally Posted by Ulzgoroth

Do you have any criticism of the TS rules other than that they assume that you can hit with differing rounds while you prefer to assume that you can't? Because there might be good criticisms but I don't think you've specified any.

Let's look at the Sgt Barry Wunder example: 10 round burst of 4:1 standard:tracer.

The basic way using ammunition of varying ballistics works is that you get two separate hit patterns, each centered where you'd expect from the ballistics of the particular round involved.

At a range where the patterns are separated by less than the target size, the expected number of hits for mixed ammo is identical the number of hits from non-mixed ammo, and thus we should just resolve this as RoF 10 (skill 10, +2 for RoF, roll of 8, so 3 hits) and there's about a 60% chance that one of the hits was a tracer. Tactical Shooting produces 2 hits.

At a range where the patterns are separated by more than the target size, you have to choose which ammo type you're trying to match, and if you hit, all the hits will be the same ammo type (generally the one you picked, though there's always a chance you'll miss by exactly the right amount for the other to hit). This should just base accuracy on the number of rounds of the correct type, but then prorate hits based on the fraction of bullets that are that type, ignoring the other type entirely (so 2 hits of solid, most likely).