Let's say a particular theoretical (because I can't remember numbers off-hand right now) gun has the following stats:

Regular ammo: 100 damage
AP: 95 damage, -15 DT
HP: 175 damage, x3 DT
JSP: 150 damage

Now say I have 4 targets.
Target 1: DT 0
Target 2: DT 10 (Not terribly uncommon)
Target 3: DT 30 (T51-b power armor + helmet, legendary deathclaw)
Target 4: DT 45 (I'm not sure if something actually has this much DT)

Assuming no crits, the following damage will be dealt:
AP: 95, 95, 80, 65
HP: 175, 145, 85, 40
JSP: 150, 140, 120, 105

If we change the weapon to a rapid firing one that does 20 damage a shot rather than 100 with regular ammo, we'd have:
AP: 19, -15 DT
HP: 35, 3x DT
JSP: 30

And against the same targets of 0/10/30/45 DT:
AP: 19, 19, 4, 0
HP: 35, 5, 0, 0
JSP: 30, 20, 0, 0

So I have some questions...
Are this calculations correct?
Does damage reduction apply before or after DT removes damage?
Does a crit also multiply the DT reduction (thus a 2x crit would do 190 damage and -30 DT)?
It seems JSP is almost always better than AP, except in a small window (~20 damage rounds vs ~12+ DT), which makes sense from a balance perspective because JSP rounds are hand loaded and require more work in-game.
It seems AP rounds in high base damage guns (in .308 and .50 particularly) are pretty much worthless; HP rounds do more damage against all but ridiculously high (impossibly high?) DT.
It seems HP rounds in low base damage guns are almost worthless if the target has any armor better than merc/wastelander gear.

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So I made a spreadsheet to figure this out, in increments of 10 damage base and 5 DT.

At 0 DT, HP is always better, regardless of ammo.
At 5 DT, JSP is the best up until 40 base damage, then HP.
At 10 DT, AP is best at 10 damage, then JSP until 140 damage, then HP.
At 15 DT, AP is best until 20 damage, then JSP until 130, then HP.
At 20+ DT, AP is best until 20 or so, then JSP.

Looking at it another way, it's almost always best to use AP rounds in ~20 damage or less per shot weapons, like the assault and marksman carbines, service rifle, ratslayer, 10mm pistol, Maria, That Gun, light machine gun, all the miniguns, all the shotguns, and all the SMGs. Sure at low DT it's technically better to use HP, but you're doing so much damage anyway that it doesn't matter.

At 30 damage per shot or higher, if given the option, I'd always take JSP (1.5x damage with no DT modifier) over any other round.

Hollow points also out perform AP rounds across the board in some situations. An anti-material rifle, for example, will always do more damage with hollow points than with armor piercing until you hit a target with more than 35 DT. And besides the player, I can't think of anything in the game with more than 35 DT.

Here is how i deal with this:

If it looks like a Deathclaw i run away.

If it looks like a Giant Radscorpion i think about shooting it before running away.

If it looks like something that has armor i shoot it with AP.

If it looks like something that doesn't have armor i shoot it with hollow points.

If it looks like a bloatfly i shoot it with regular ammo.

This seems to work well.

A JSP to the head from a sniper rifle while sneaking will kill deathclaws in one hit. If it's silenced, you can sneak attack crit all of them.

so true, death claws at the quarry, take out the few at the entrance then perch up on the coal tower thing and go to town. i was having so much fun i didnt care about the 1000's of caps in ammo i was wasteing :laugh:

You are oversimplifying it though OP. Doesn't JSP (150% dmg) only come in .308 flavour, which is only used in snipers and hunting rifles?

Also if I read something correctly even when your weapons damage is below the DT threshold a small portion of the damage will still get through which will allow you to 'nibble' your opponent to death so to speak.

Yeah I actually didn't realize that, I was just using .308 for example because it was the only one with all three.

So nevermind my anolysis. But is this how DT works?

All this, of course, assumes you have infinite amounts of each ammo type. When you have 500 normal, 50 AP, and 0 JSP, you tend to use the normal ammo most of the time, and save the AP for only the toughest targets.


Edit: you know, I've never used hollow point ammo. I don't have the perk that lets me see DT values, so I'm never sure what has no armor. And anyway, anything with no armor will die easily enough to regular ammo, why waste the time switching it.....