Overhaul civilian ammunition appearance rates.

[kevingranade]

Is your feature request related to a problem? Please describe.

Ammunition appears in game in essentially arbitrary ratios, leading to an exaggerated difficulty when finding matching guns and ammunition.
In the opposite direction, particularly rare ammunition is not remotely as rare as it should be.

Describe the solution you'd like

Spawn guns and ammo (but focusing on ammo here) in representative ratios.
Specifically I've done some figuring with some hopefully representative data points and come up with some distributions for the most common ammunition types, and item lists referencing ammunition drops can spawn ammo in those ratios.

EDIT: This is a summary, the full table is below, but it's too unwieldy so I'm putting this summary here.

Calibre	Percent Revenue	Price/rd	Proportion of Rounds Sold
.22LR	0.0512	0.038	0.20416406493382
9mm	0.1776	0.13	0.209353199429958
.223	0.12	0.2	0.094910636269089
.45	0.0858	0.27	0.049387315857842
.40	0.0602	0.23	0.040081682049504
12ga	0.0434	0.25	0.026452313112003
7.62	0.0417	0.19	0.034383554038087
.38	0.0244	0.19	0.019415881708033
.308	0.05285	0.33	0.02511926393844
5.56	0.0756	0.41	0.029482088663224
		Remainder →	0.26725

Another even more simplified tabulation:

Round type	Proportion
Tiny	20%
Pistol	32%
Intermediate	16%
Shot	2.6%
Rifle	2.5%
Other	27%

Points of interest

9mm and .22 make up 40% of all civilian ammunition.
.223 is a distant but significant third at 9.5%.
.45 and .40 are an even more distant 4th and 5th, but (along with the rarer .38) bring "medium pistol rounds" up to 30% of civilian ammunition.
12ga is sitting at a rare but not incredibly rare 2.6%
Intermediate rounds (.223, 7.62 and 5.56) sum to a respectable 16%.
Traditional rifle rounds are quite low at just over 2.5%
"and the rest" is 27%, which spread evenly across the 33 remaining ammo types is going to make them incredibly rare ( 0.8% ).

Side note, this is civilian ammunition, not police or armed forces, which will follow a totally different distribution and need their own sources.

Data

Retrieved a (hopefully representative) snapshot of sales stats from https://www.luckygunner.com/labs/2013-ammo-stats/
Retrieved prices per round from the same site.

2012 data

Calibre	Percent Revenue 2012	Price/rd	Rounds per Dollar Revenue 2012	Proportion of Rounds Sold 2012
.22LR	0.0344	0.038	0.905263157894737	0.153910988675132
9mm	0.1412	0.13	1.08615384615385	0.184665653138481
0.223	0.138	0.2	0.69	0.117312387298312
0.45	0.0816	0.27	0.302222222222222	0.051383203454333
0.4	0.0474	0.23	0.206086956521739	0.035038482406679
12ga	0.0318	0.25	0.1272	0.021626283571515
7.62	0.0434	0.19	0.228421052631579	0.038835679700586
0.38	0.0158	0.19	0.083157894736842	0.014138335006204
0.308	0.0557	0.33	0.168787878787879	0.028696969576267
5.56	0.0962	0.41	0.234634146341463	0.039892017172491
SUM →	0.6855	SUM →	4.03192715529031	0.3145
		SCALED →	5.88173180932211	^ Remainder

2013 data

Calibre	Percent Revenue 2013	Price/rd	Rounds per Dollar Revenue 2013	Proportion of Rounds Sold 2013
.22LR	0.068	0.038	1.78947368421053	0.254417141192509
9mm	0.214	0.13	1.64615384615385	0.234040745721435
0.223	0.102	0.2	0.51	0.072508885239865
0.45	0.09	0.27	0.333333333333333	0.04739142826135
0.4	0.073	0.23	0.317391304347826	0.045124881692329
12ga	0.055	0.25	0.22	0.031278342652491
7.62	0.04	0.19	0.210526315789474	0.029931428375589
0.38	0.033	0.19	0.173684210526316	0.024693428409861
0.308	0.05	0.33	0.151515151515152	0.021541558300614
5.56	0.055	0.41	0.134146341463415	0.019072160153958
SUM →	0.78	SUM →	5.48622418733989	0.22
		SCALED →	7.03362075299986	^ Remainder

Process

All steps repeated for 2012 and 2013 data.
Multiplied proportion of revenue by price per round to get "Rounds per dollar of revenue".
Summed "Rounds per dollar of revenue" figures to get "aggregate rounds per dollar of revenue".
Scaled Aggregate rounds per dollar of revenue by 78% to get "Adjusted rounds per dollar of revenue".
Divided each "Rounds per dollar of revenue" by "adjusted rounds per dollar of revenue" to get "proportion of rounds sold".
Averaged together "proportion of rounds sold" from 2012 and 2013 for each calibre.
Additionally, summed "Proportion of rounds sold" to determine how much of the market is covered, which yields the 31%/22%/26% remainder for "proportion rounds not in the top 10".

Describe alternatives you've considered

All the other options are totally subjective, and I'm not a fan. If anyone finds other qualitative sources for this I'd love to try and incorporate them.
Possibly we can bucket the remaining ammo types into low and high or low/med/high to put a little extra scaling on them instead of just having them evenly represented.

[Brian-Otten]

This sounds like a good way to approach it, although we should also take care to make ammo spawn in portions that make sense. You wouldn't likely find 3 12 gauge shotgun shells in someones house, you would either find 0 or find his spare box of ammo.

Implementation wise, how would we spawn the ammo types in the mentioned proportions while also making loot feel right? I'm thinking perhaps make sus itemgroups for the common calibers, which have a chance to include a gun and some suitable magazines.

Then one would have all of the groups set to spawn, and set their spawnchance using the data from this post.

[TechyBen]

What would the assumed "used" or "decay" be? Time has passed, and lots of things would be used up in the time before the survivor gets there.. So this does allow for some balance outside of "loot" (untouched) locations, right?

[Brian-Otten]

Current assumption is "post-cataclysm" looting by survivors will be eventually implemented. So things get looted as the game progresses. The amount of guns/ammo missing in the spawngroups would be based on estimates of how much is used up/taken on average by the people directly experiencing the cataclysm.

[CSHague]

Civilian ammo is typically packaged in cardboard packs and boxes; or in plastic tray-cases. Could separate between loose round spawns and packaged spawns and guarantee that unlooted commerical packages would be full (no one who looted a place would just take a couple rounds out) while looted packages in homes and other places will have random amounts similar to household chemical spawns.

[kevingranade]

Yes the number of rounds would be divided by the appearance rate, so in a gun store the boxes wouldn't spawn in these ratios, the rounds would.

My plan for achieving this distribution is to run a test that runs over an overmap or so worth of mapgen and tallies up the number of rounds spawned. Probably the first cut would be to determine a set of ratios for all the rounds based on the above data, then see where that gets us because the chaotic interaction of item groups and mapgen is going to make the final outcome unpredictable. From there it's just a matter of tweaking those numbers until the final spawn rates come out right.

[Brian-Otten]

We might also want to think about doing some kind of estimate of how much and what ammo is used during the cataclysm itself. I might imagine not a lot of the .22 ended up being used when shit hit the fan, and the rare collector guns also not seeing much use, but the 9mm and .223 might have seen a lot of use before the end really hit.

[kevingranade]

After polishing up that top 10 list and looking at some in-game numbers, I REALLY need to have some additional adjustment for the remaining 30-odd calibres of civilian ammunition, because the kind of naive thing to do is to evenly divide the remaining "unreported" proportion of calibres among them, but that's definitely wrong as some of them are probably barely off the bottom of the top 10 list and others are almost unheard of.

[stale]

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[kevingranade]

See http://knowledgeglue.com/what-are-the-most-popular-calibers-in-the-us/ for additional potentially useful data, though it will need to be massaged a bit since it is by units sold, so we need to make assumptions about how many rounds are typical.

[kevingranade]

Here's the data from knowledgeglue tablulated

Calibre	Units Sold	Round class	Est. Unit size	Estimate number of rounds	Note	Percentage
9mm Luger	5986	Pistol	50	299300		0.184713749232417
.223 Civ	3390	Rifle	20	67800	Split back out	0.041842940855188
5.56 NATO	1695	Rifle	20	33900	Split back out	0.020921470427594
45 ACP	4212	Pistol	50	210600		0.129972320709479
12 Gauge (birdshot)	3540	Shotgun	25	88500	Assuming these are birdshot	0.05461799801894
22 Long Rifle	3402	0.22LR	100	340200		0.209955287299927
40 S&W	2126	Pistol	50	106300		0.065603312874727
380 ACP	1550	Pistol	50	77500		0.047829320299072
308/7.62 NATO	1546	Rifle	20	30920		0.01908235591803
7.62x39	1340	Rifle	20	26800		0.016539687535679
357 Magnum	1114	Pistol	50	55700		0.034375395363333
38 S&W Special	851	Pistol	50	42550		0.026259839725491
40 cal	718	Rifle	20	14360	Black Powder?	0.008862310187028
30-06	691	Rifle	20	13820		0.008529047826235
20 Gauge	517	Shotgun	25	12925	Assuming Birdshot	0.007976696320845
44 Magnum	490	Pistol	50	24500		0.015120236739707
30-30	334	Rifle	20	6680		0.00412257883352
7.62x54R	332	Rifle	20	6640		0.004097892732721
50 Black Powder	299	Rifle	20	5980		0.003690572069528
270 Winchester	265	Rifle	20	5300		0.003270908355937
45 Long Colt	253	Pistol	50	12650		0.007806979377849
243 Winchester	214	Rifle	20	4280		0.002641412785549
7mm Remington Magnum	214	Rifle	20	4280		0.002641412785549
12 Gauge (buckshot and slugs)	205	Shotgun	5	1025	Assuming these are buck/slugs	0.000632581332988
300 Blackout	197	Rifle	20	3940		0.002431580928753
17 HMR	183	Rifle	100	18300		0.011293891115781
22 WMR	181	Rifle	20	3620		0.002234092122357
410	169	Shotgun	25	4225	Assuming Birdshot	0.002607469396949
22 Magnum	158	Pistol	100	15800		0.009751009815811
8mm Mauser	152	Rifle	20	3040		0.001876143660764
300 Winchester Magnum	149	Rifle	20	2980		0.001839114509564
16 Gauge	136	Shotgun	25	3400	Assuming Birdshot	0.002098318567959
5.45x39mm	122	Rifle	20	2440		0.001505852148771
32 ACP	113	Pistol	50	5650		0.003486911737932
25 ACP	107	Pistol	50	5350		0.003301765981936
357 SIG	105	Pistol	50	5250		0.003240050729937
38 S&W	90	Pistol	50	4500		0.002777186339946
4570 Government	84	Rifle	20	1680		0.00103681623358
50 BMG	78	Rifle	10	780	Assuming Civilian boxes	0.000481378965591
30 Carbine	77	Rifle	20	1540		0.000950414880782
9mm Makarov	77	Pistol	50	3850		0.002376037201954
303 British	72	Rifle	20	1440		0.000888699628783
7.62x51mm NATO	68	Rifle	20	1360		0.000839327427184
338 Lapua	64	Rifle	20	1280		0.000789955225585
300 Winchester Short Magnum	59	Rifle	20	1180		0.000728239973586
500 S&W	55	Pistol	50	2750		0.001697169429967
5.7x28mm	54	PDW	20	1080		0.000666524721587
6.8mm SPCII	54	Rifle	20	1080		0.000666524721587
454 Casull	50	Pistol	50	2500		0.00154288129997
28 Gauge	46	Shotgun	25	1150	Assuming Birdshot	0.000709725397986
10 Gauge	40	Shotgun	5	200		0.000123430503998
204 Ruger	39	Rifle	100	3900		0.002406894827953
270 WSM	39	Rifle	20	780		0.000481378965591
25-06 Remington	38	Rifle	20	760		0.000469035915191
35 Remington	36	Rifle	20	720		0.000444349814391
338 Winchester Magnum	35	Rifle	20	700		0.000432006763992
38 Super	35	Pistol	50	1750		0.001080016909979
44 Special	32	Pistol	50	1600		0.000987444031981
6.5x55 Swedish	31	Rifle	20	620		0.000382634562393
22 Short	31	0.22	100	3100		0.001913172811963
7mm-08	31	Rifle	20	620		0.000382634562393
10mm	30	Pistol	50	1500		0.000925728779982
300 Weatherby Magnum	28	Rifle	20	560		0.000345605411193
45 GAP	27	Pistol	50	1350		0.000833155901984
45 Black Powder	27	Rifle	20	540		0.000333262360794
222 Remington	26	Rifle	20	520		0.000320919310394
54 Black Powder	24	Pistol	20	480		0.000296233209594
30-40 Krag	20	Rifle	20	400		0.000246861007995
223 WSSM	19	Rifle	20	380		0.000234517957595
6.5 Creedmoor	19	Rifle	20	380		0.000234517957595
458 SOCOM	17	Rifle	20	340		0.000209831856796
280 Remington	16	Rifle	20	320		0.000197488806396
44 Black Powder	16	Pistol	20	320		0.000197488806396
45 Colt	16	Pistol	50	800		0.00049372201599
450 Bushmaster	15	Rifle	20	300		0.000185145755996
300 Remington Ultra Mag	15	Rifle	20	300		0.000185145755996
32 Winchester Special	15	Rifle	20	300		0.000185145755996
50 Beowulf	14	Rifle	20	280		0.000172802705597
7.5x55 Swiss	14	Rifle	20	280		0.000172802705597
44-40 Winchester	13	Rifle	20	260		0.000160459655197
7mm Mauser	13	Rifle	20	260		0.000160459655197
444 Marlin	13	Rifle	20	260		0.000160459655197
6mm Remington	13	Rifle	20	260		0.000160459655197
327 Magnum	13	Pistol	20	260		0.000160459655197
7.62x25 Tokarev	13	Pistol	50	650		0.000401149137992
260 Remington	13	Rifle	20	260		0.000160459655197
22 Hornet	12	Rifle	20	240		0.000148116604797
6.5x52 Carcano	12	Rifle	20	240		0.000148116604797
450 Marlin	11	Rifle	20	220		0.000135773554397
375 H&H Magnum	11	Rifle	20	220		0.000135773554397
7.7x58 Japanese	11	Rifle	20	220		0.000135773554397
257 Weatherby Magnum	11	Rifle	20	220		0.000135773554397
Total units ->	38888		Total estimated rounds ->	1620345

[jbytheway]

Once you have this data finalized I encourage you to record the data and sources in the repo for future reference.