How to play sound clip overlay many times

Mix_PlayChannel(-1, m_chunk, 0);

I use the code upon to play the gun fire sound effect.
I call the function 10 times per second.
One sound clip play time is more than 100 ms.
I heard less than 10 sound, and then the sound gone, and then I can heard less than 10 sound.

I think I need to set the sound buffer size, means that, how many sound can play overlay.
So I want to know, in SDL how to set element count of sound buffer?