Shortening an inner barrel

Howdy again r/airsoft,

I was going to purchase myself this front-end conversion kit to make my Raider more CQB-ready, as the field I play at has some rather tight spaces, and I already have an AK for mid-range stuff. My problem is an inner barrel. The one on my Raider is much too long (almost 4.5 inches) for the kit and it doesn't come with the required 300mm one. I am on a tight budget and can't affor the 100$ price tag of getting a new inner and the kit, so I need to shorten my existing one. I have a couple of questions a. Is this just a terrible idea in general (shortening my prexisting barrel) and b. How should I go about cutting it down to size. Thanks!