While I was seeing I got my resistance drained a lot, I started thinking that there could be a new strategy if there were also Bullet & Rocket drainers! These could make ammo mechs cry, and make them less OP! So, the stats are here:

Bullet Drain
Epic Item
40 Weight
15 Bullet Drain
1 Use
+15 Heat Per Use
-20 Energy Per Use

Rocket Drain
Epic Item
41 Weight
15 Rocket Drain
1 Use
+20 Heat Per Use
-15 Energy Per Use

Bullet Drainer
Epic Item
46 Weight
20 Bullet Drain
1 Use
+18 Heat Per Use
-23 Energy Per Use

Rocket Drainer
Epic Item
47 Weight
20 Rocket Drain
1 Use
+23 Heat Per Use
-18 Energy Per Use

Bullet Explosive
Legendary Item
49 Weight
25 Bullet Drain
1 Use
+20 Heat Per Use
-25 Energy per Use

Rocket Explosive
Legendary Item
49 Weight
25 Rocket Drain
1 Use
+25 Heat Per Use
-20 energy Per Use

And an extra for those of you who don't want to be selective...
Bullet & Rocket Drain Mark I
Legendary Item
54 Weight
10 Bullet Drain
10 Rocket Drain
1 Use
+23 Heat Per Use
-23 Energy Per Use

Bullet & Rocket Drain Mark II
Mythical Item
59 Weight
15 Bullet Drain
15 Rocket Drain
1 Use
+26 Heat Per Use
-26 Energy Per Use

Bullet & Rocket Explosive / Bullet & Rocket Drain Mark III
Mythical Item
64 Weight
20 Bullet Drain
20 Rocket Drain
1 Use
+30 Heat Per Use
-30 Energy Per Use

Like it, or does it need a tweak?
Also, adding an extra condition:
You cannot use more than one Drainer of a type.
For example:
You are using Bullet Drainer. You can use Rocket Explosive, but you CAN'T use Bullet Explosive nor Bullet Drain, and viceversa. And, if you are wearing ANY single ammunition drainer, you CANNOT use any Bullet & Rocket drainer, and viceversa.
This rule is put for avoiding the massive drain of ammunition.