It make the shortgun be reloaded too frequently. As a result, players get too much items. And that cause 2 problems.
One of them is that some players don't have a chance to move . Because others can use the 2 new items to skip his turn easily as they have more items.
Another problem is that the game duration will be too long as players can use cigarette more frequently and they have to spend more time on thinking as they can get items.
So, maybe more shells should be loaded at the same time in a 4 players game so players will get fewer items. But the number of shells is perfect in a 2 or 3 players game.