As written, a [backpack Ammo Supply] grants a weapon five times its clip size in exchange for 15kg and five minutes of strictly out-of-combat reload time. Multiplication rears its ugly head here: a big numbers get bigger while smaller numbers stay small. It strikes me as odd that the same 15kg worth of backpack can hold 300 Lasgun rounds but only 5 Laslock charges, or 10 Hand Flamer bursts but 50 Heavy Flamer bursts. The examples go on and on. Pistols that presumably use less space for their ammunition, less energy for their beams, or less fuel for their flames somehow utilise a giant backpack worse than a heavier weapon. Often much worse. How does that make any sense?

What are your thoughts on the Backpack Ammo Supply? I would want to give lighter, weaker weapons an appreciably larger clip while preventing heavier, stronger weapons from benefiting too much. I am not sure that there is a nice clean answer to solve this issue. Going back to [Only War]'s backpack is not a fix since the 15kg backpack holds 200 Autopistol rounds just as well as 200 Heavy Bolter rounds. Flat ammunition grants are pretty much as nonsensical as multiplication.

The simplest solution is probably just "*sunglasses* Deal with it".

NEW ADDENDUM (credited to [Nimsim]):

A Backpack Ammo Supply grants infinite ammo (within reason) for one combat encounter. It is always empty at the end of a combat in which it is used. Should a backpack-linked weapon Jam, the weapon does not need to be reloaded and the backpack's capacity is not affected. The character still needs to take proper measures to un-Jam the weapon.

OLD ADDENDUM:

What if the Backpack Ammo Supplies doled out clips of 1000 Damage ( already calculated below )? For calculations, divide 1000 by the weapon's maximum damage, round that to the lowest 10, and subtract 20 from non-Pistol weapons. In effect, treat d10s as 10s, so a 1d10+7 weapon would have a maximum damage of 17. Take that 17 and divide 1000 by it, which results in 58.82. Rounding that down to 50 shows how much 17 damage ammunition a backpack can hold.

Pistols generally have shorter range, so this penalty reflects the extra propellant or what have you that larger weapons can afford. That way, the smallest caliber weapons would see a healthy increase while big impact weapons don't get as much mileage. This approach also has the benefit of simulating ammo size since large bullets would reasonably take up more space in a set size backpack.

Here's a table of pre-calculated values:

Maximum Weapon Damage || Backpack Capacity

10 || +100

11 || +90

12 || +80

13, 14 || +70

15, 16 || +60

17, 18, 19, 20 || +50

Apply a -20 penalty to the Backpack's Capacity if the weapon is of the Basic or Heavy class.

_______________

1. There may be cases where backpack-linked Basic weapons get an equal or larger amount of ammo capacity than backpack-linked pistols of a similar class. As this is an exception rather than a rule, I believe a further -10 penalty on any Basic weapon would be appropriate to maintain a proper tradeoff.

2. There are even situations where a weapon can be so strong that a backpack provides no benefit or an [Expanded Magazine] would do more. With the Autocannon in particular, it is ridiculous that a backpack can hold 120 rounds of 3d10+8 I damage as written. For these rare cases, I believe the backpack should guarantee at least the weapon's clip and a half of ammo, the same bonus as an Expanded Magazine. These rare cases are also denied the Expanded Magazine modification, meaning that stronger weapons can only rely on heavy backpacks for increased ammo capacity.

The backpack adds to the weapon's original clip rather than replacing it. What do you think of this perspective?

I'd say have a fixed amount of ammunition based on the type of ammunition. You'd need to create a new lookup table for it.

So for example:

- 300 lasgun rounds

- 200 bullets

- 100 Bolter rounds

- 50 flamer bursts

- ...

Note, these are just arbitrary numbers, I've no idea what would be realistic.

Even categorizing ammo backpacks by type, 200 Solid Projectile rounds has varying mileage between ends of the spectrum. On the one end, there's little Stub Automatics. On the other, Heavy Stubbers. 15kg somehow accommodates both weapons equally, which is my problem. And that's without going to things like 200 sniper rifle rounds vs to 200 shotgun shells.

Well, then you're going to have to divide the 15kg by the weight of a single ammunition round of a particular type to have anything realistic. With the parameters given, you're never going to get something realistic/accurate.

That said, I agree that there is a problem with the formula that they stated. It's an oversimplification that's absurd in certain situations as you pointed out.

*sun glasses*

I just go with one unique ammo supply per unique weapon. i.e. you can't use a Heavy Bolter ammo supply for another weapon but a Heavy Bolter, you would have to acquire a new backpack ammo supply for that specific weapon .

Yeah, it's just the oversimplified nature of the Backpack Ammo Supply that bothers me. As written, it's completely illogical how a storage unit can work that way. The [Expanded Magazine] by comparison is fine since its expanding on the weapon's own traits, such as making a 6-cylinder grenade launcher into a 9-cylinder one just by obtaining a bigger drum. Even for massive belt-fed guns, it could be as simple as procuring a longer belt. Still, it has the same problems by making one-shot weapons just two-shot weapons. That's not helping anyone.

It's not specific weapons I'm worrying about. It's how two different backpacks, run by the same principles, can have drastically different capacities. A Heavy Bolter's backpack has 60x5, yes? Then a Bolt Pistol's backpack would only have 8x5 despite both being Bolt weapons. This is my problem. The same upgrade applies drastically differently between items.

Different caliber, different loading mechanisms.

The moral of the story is don't use backpack ammo supplies on pistol weapons. It's dumb, but there it is.

Correct me if I'm wrong, but didn't the Fire Selector upgrade used to not have the bit about not increasing the weapon's capacity? In my group that was a common way to increase your magazine size. Very useful for low-capacity weapons.

An ammo backpack supply is really only relevant to heavy weapons and maybe las guns. Pistols and so forth just aren't large enough to be belt fed ammo. In this case it wouldn't take a very large list to create weapon specific backpacks.

Don't Hellpistols already come with a sort-of backpack power supply? So at least for lasweapons there's precedent and it's not like IRL where the bulk of the backpack would defeat any point of using a pistol. In WH40k you might want to stick with a pistol and a melee weapon, for example.

More like a fanny-pack ammo supply for the Hell pistol. Same for the Hellgun IIRC. Sort of. The newest storm trooper models from GW have backpacks that appear to have a really big, swap-able power pack. The Hellpistol doesn't plug into the backpack though, just the Hellgun.

I suggest you just disregard the "multiply by 5" rule and create a unique clip size for each weapon that could reasonably use a backpack ammo supply. There should be downsides to using one and almost never requiring a reload. Something like exclusion of the Fire Selector for bolt weapons fed from an ammo supply.

According to Only War both of them have a 10kg backpack power supply (which you can still reload... somehow?!).

Thank you for your replies, everyone.

It's the discrepancy between shoving Pistol ammunition and Heavy ammunition in the same upgrade that bothers me most. However, even taking Pistols out of the equation, there are still Basic weapons with small clips and Heavy weapons with large clips. The root problem, the multiplication, is still there. Giving each and every weapon its own Backpack clip size kind of defeats the purpose of having a "universal" upgrade. Long story short, I just don't like the Backpack Ammo Supply as written.

I tried solutions such as scaling the Backpack's weight with the ammunition that's put in, but doesn't change how smaller clip weapons see the smallest benefit. Then there was filling the Backpack with 15kg worth of ammunition, but that can get even worse than the multiplicative system. Letting weapons get a minimum and maximum benefit of 20 and 200 backpack rounds is the compromise I found most suitable, but big clip Heavy weapons still win out.

The amount of ammo in the backpack should probably also be balanced against the lethality of the weapon as well.

What if the Backpack Ammo Supplies doled out clips of 1000 Damage? For calculations, assume each 1d10 gives 10 damage, ignore Pen, always round down to the next lowest 10, and subtract 20 from non-Pistol weapons. Pistols generally have shorter range, so this penalty reflects the extra propellant or what have you that larger weapons can afford. That way, the smallest caliber weapons would see a healthy increase while big impact weapons don't get as much mileage. This approach also has the benefit of simulating ammo size since large bullets would reasonably take up more space in a set size backpack. Some examples:

Bolt Weapons

Bolt Pistol, 15 Damage | Clip size 8 -> 8 + (66.67). Round to 60 for a total clip size of 68.

Bolt Gun, 15 Damage | Clip size 24 -> 24 + (66.67 - 20). Round to 40 for a total clip size of 64.

Heavy Bolter**, 18 Damage | Clip size 60 -> 60 + (55.56 - 20). Round to 30 for a total clip size of 90.

Flame Weapons

Hand Flamer, 14 Damage | Clip size 2 -> 2 + (71.42). Round to 70 for a total clip size of 72.

Hand Flamer, 14 Damage | Clip size 6 -> 6 + (71.42 - 20). Round to 50 for a total clip size of 56.

Heavy Flamer, 15 Damage | Clip size 10 -> 10 + (66.67 - 20). Round to 40 for a total clip size of 50.

Las Weapons

Laspistol, 12 Damage | Clip size 30 -> 30 + (83.33). Round to 80 for a total clip size of 110.

Lasgun*, 13 Damage | Clip size 60 -> 60 + (76.92 - 20). Round to 50 for a total clip size of 110.

Melta Weapons

Inferno Pistol, 30 damage | Clip size 3 -> 3 + (33.33). Round to 30 for a total clip size of 33.

Melta Gun, 30 damage | Clip size 5 -> 5 + (33.33 - 20). Round to 10 for a total clip size of 15.

Plasma Weapons

Plasma Pistol, 16 damage | Clip size 10 -> 10 + (62.50). Round to 60 for a total clip size of 70.

Plasma Gun*, 17 damage | Clip size 40 -> 40 + (58.82 - 20). Round to 30 for a total clip size of 70.

Solid Projectile Weapons

Autopistol, 12 damage | Clip size 18 -> 18 + (83.33). Round to 80 for a total clip size of 98.

Autogun, 13 damage | Clip size 30 -> 30 + (83.33 - 20). Round to 60 for a total clip size of 90.

Autocannon**, 38 damage | Clip size 24 -> 24 + (26.31 - 20). Rounding to 20 does not increase total clip size.

_______________

* There may be cases where backpack-linked Basic weapons get an equal or larger amount of ammo capacity than backpack-linked pistols of a similar class. As this is an exception rather than a rule, I believe a further -10 penalty on any Basic weapon would be appropriate to maintain a proper tradeoff.

**There are even situations where a weapon can be so strong that a backpack provides no benefit or an [Expanded Magazine] would do more. With the Autocannon in particular, it is ridiculous that a backpack can hold 120 rounds of 3d10+8 I damage as written. For these rare cases, I believe the backpack should guarantee at least the weapon's clip and a half of ammo, the same bonus as an Expanded Magazine. These rare cases are also denied the Expanded Magazine modification, meaning that stronger weapons can only rely on heavy backpacks for increased ammo capacity.

The backpack adds to the weapon's original clip rather than replacing it. What do you think of this perspective?

You're making this way too complicated, dude.

You're making this way too complicated, dude.

I'm just trying to fix a realism/logic hole.

There's a point where plugging the hole makes a different more difficult to deal with hole.

I mean it's a decent fix, well described, but so much bookeeping that it's unappealing to my eyes at least.

There's a point where plugging the hole makes a different more difficult to deal with hole.

I mean it's a decent fix, well described, but so much bookeeping that it's unappealing to my eyes at least.

Any "fix" I make would require a lot of bookkeeping, though that's more of a personal quirk. Part of me wants to argue that 1000/Damage per backpack doesn't require much effort, but the fact that it requires more than one mathematical operation already overcomplicates what should be a no-brainer upgrade. Continuing anyway, weapon Damage can be put on a nearly catch-all scale of 1d10 to 2d10. This means that a backpack's capacity could be generated by looking at a table for values 10-20. Rounding could already be included in the table, with a note to apply -20 to non-Pistol weapons. Like so:

Damage || Backpack Capacity

10 || +100

11 || +90

12 || +80

13 || +70

14 || +70

15 || +60

16 || +60

17 || +50

18 || +50

19 || +50

20 || +50

When all the math is already done for the user, it's a little bit simpler. Now that I think about it, I could have just said this outright.

EDIT: Put this in the original post instead of all the mumbo-jumbo I had before. I should have done this in the first place.

Maybe it's just me, but I don't really understand your updated math.

It just reads like an encumberance table that's more complicated than it should be.

But hey, if it works for you that's important.

Maybe it's just me, but I don't really understand your updated math.

It just reads like an encumberance table that's more complicated than it should be.

But hey, if it works for you that's important.

All I did was create a table with the most common damages of weapons that would want a Backpack Ammo Supply. The end numbers are exactly the same as I had them before, I just did the math in advance.

EDIT: Tried to make the post simpler by trimming off redundant table entries. Basically, a Backpack Ammo Clip is 1000/Maximum weapon damage, rounded to the next lowest ten. A weapon with 17 Maximum Damage (1d10+7) would have a calculation of 1000/17 or 58.8. Round that down to 50 and that's how much of an extra clip a backpack would give.

Why not just have a flat amount of ammo (like 200) it provides and have the weight be that amount times a fraction of the weapon's weight?

Or, more sensibly in my opinion, just say that wearing and carrying a backpack effectively gives infinite ammo to whatever weapon using it for the entirety of a game session? After using it for one session, rolling a "jam" result will mean that it's run out of ammo and needs to be refilled. If you really want to balance it out a bit more, have its weight be something like weapon weight*5 or *10 and base the rarity on the weapon its being used for -10. Or, if your game is combat heavy, have it last for one scene/encounter before jamming causes it to run out.

I know that if you're making weight and ammo tables, that this kind of solution probably won't appeal to you that much. On the other hand, having a literal barrel on your back feeding you ammo in a game like dark heresy is pretty much the thematic equivalent of "infinite ammo." A player is going to have to try really hard to use up 200 shots, especially in all these games I'm reading about on here where GMs want players to avoid combat.

Or, more sensibly in my opinion, just say that wearing and carrying a backpack effectively gives infinite ammo to whatever weapon using it for the entirety of a game session? Or, if your game is combat heavy, have it last for one scene/encounter before jamming causes it to run out.

This... I actually like this solution. Simple, yet elegant. Backpack Ammo Supplies aren't something to wear on an everyday trip after all. A character doesn't put one on just for the increased capacity, they put it on in anticipation of a large battle. I would say that wearing a Backpack Ammo Supply grants infinite ammo (within reason) but always expires at the end of a combat in which it is used. I would let Jams be more lenient though, if I was to restrict use of a Backpack Ammo Supply. The few Turns penalty the character needs to spend fixing his ammo supply should be enough.

Thank you very much for this perspective.

Eh, it's obviously made with heavy weapons in mind. Take a standard heavy weapon of ammo type X's clip size. Multiply it. Apply to all weapons of that type. Fixed.