CoD4 Shared Ammo
Here is a list made by buddhamonster that shows which Call of Duty 4 weapons share ammo, so that you can select them together (most of them would require the "Overkill" perk so you can select two primary guns.), and have an extra ammo boost. Kind of like bandolier, but without wasting a perk...
If this list is missing something or you see an incorrect usage, please contact me and let me know. Also thanks to Kilgore777 from our forums for finding this information and The PFC for updating it!
Ammo sharing weapons:
7.62x39 / 7.62x51 - RPD, M60, AK47 cannot be combined with other weapons.
7.62x54 - Dragunov Also cannot be combined with any other weapons.
7.62 round - M14, M21, G3, M40A3, R700
.45 round - M1911, USP
9mm round - M9, MP5, Mini-Uzi
5.45 round - AK74u
5.56x45 - M16, M4, G36C
5.56x45 - SAW (Cannot be combined with other weapons.)
.50 round - Barret
.50 round - Desert Eagle (Does not combine with barret)
12 gauge - M1014, W1200
7.92 round - MP44
9x18 round - Skorpion
5.7x28 round - P90
Here is another list compiled by Luft:
7.62 X 39 mm * AK-47 7.62 X 39 mm (belt) * RPD 7.62 x 54 mm R * Dragunov 7.62 X 51 mm NATO * M14 * M21 * G3 * M40A3 * R700 7.62 X 51 mm NATO (belt) * M60E4 .45 ACP * M1911 * USP 9 X 19 mm Luger * M9 * MP5 * Mini-Uzi 5.45 X 39 mm * AK74u 5.56 X 45 mm NATO * M16 * M4 * G36C 5.56 X 45 mm NATO (belt) * M249 SAW .50 BMG * Barret .357 Magnum * Desert Eagle 12 gauge * M1014 * W1200 7.92 x 33 mm * MP44 .32 ACP * Skorpion 5.7 X 28 mm * P90