Creating automatic weapon fire design (from Foley)?

[Onnix]

I mainly do field recordings of nature but I love designing sounds from scratch but with recorded sounds only.

I'm looking at creating semi/full automatic weapon sounds such as fire from an AK-47 or M16 and handgun sounds such as a Glock. The sounds don't have to imitate the weapon, they just need to sound like gun fire.

I'm not going to use synthesis as I'd prefer to capture sounds myself. Has anyone done this before and what sounds did you capture?