SpudFiles

I was wondering how safe it would be to use clear acrylic pipefor my metered mapp gas gun as it is alot cheaper then clear pvc that is if you get extruded acrylic pipe.

Acrylic has poor impact resistance. This is a known issue. Use polycarbonate instead.
Alternates listed as high impact strength is used where stress is a factor.
http://www.tapplastics.com/info/hiacrylic.php

Common acrylic's impact strength is so terrible that essentially any machining on the piece will fracture it. I don't suggest acrylic for anything unless impact of any sort isn't a problem.

Polycarbonate is good as Technician mentioned. PET and PETG are also good. Note that I mean "good" with an adequate pipe thickness--PET bottles obviously are not good.

Finding pipes made from these plastics would be difficult; finding tubing is not. Generally the tubing's not designed to hold pressure so some math and a high safety factor or some hydrostatic testing and a high safety factor are preferred to prevent potential problems.

Clear PVC can be much cheaper depending on where you get it. eBay has good deals if you are patient.

Clear PVC is the stuff to use. Though for those who have done high powered water rockets fluorescent tube covers are often used. They are usually reinforced with carbon braid line and epoxy, but can be used as is at lower pressures.

As I linked to in boyntonstu's thread, here's why you don't use acrylic/plexiglass in this application:

Clicky

Just try find clear PVC. If you find it impossible, you may be able to contact one of the commercial spudgunners like Gort.