It would help to know what kinds of bangs you are recording. Are these intended to be big metal clangs? Low-frequency impacts? Car crashes? What recording device are you using? Are you hearing the clipping or just seeing it on the meters?

In most cases, the key ingredients to a powerful and believable impact recording are multiple perspectives (layers), spatialization, and proper use of compression/limiting. This is all very possible to do with a single SM57, it will just take a little editing in a DAW afterward. Try recording each sound from a few different perspectives, such as: extreme closeup, a couple feet away, underneath, from above, from across the room, from around the corner, and from the next room over.

Much like recording gunshots, if you only use the closeup recording then you will only get the sharp crack of the impact —— and by the time you bring the gain up enough to catch the decay of the sound, you'd be well into clipping-land. By layering the crack of the close perspectives with the body and decay of the distant ones, you get a well-rounded impact sound with perceived size. Adding a little limiting to the whole mix can add in some punch and bring the average level up, as well.

And a word on clipping: it isn't always the worst thing in the world. With a sound like a metallic bang, it's very likely that the initial transient will clip the input, but it's often so quick that you do not perceive the distortion when you listen back. Only when the sound audibly clips for more than a few milliseconds does it become a real issue. In the end, use your ears and don't worry about red warning lights.

Good luck!