Prometheus Neo Strike Hop Up chamber help

[YingKid]

Hi guys,

 

Just wondering if anyone has had experience with the Prometheus hop up Neo Strike chamber? One of these:

 

http://shop.ehobbyasia.com/prometheus-neo-metal-chamber-strike-chamber-set-for-marui-m16a2-m4a1-1.html#.VLMbCSusV8E

 

I got my hands on one of these and I was wondering if anyone knew what the O-ring that it comes with is for (see picture in link above). I have managed to put everything together but I couldn't see where I should be putting the O-ring. Any ideas?

 

Where the screw is meant to screw down to hold the final cog, I found that it didn't have any threading. Did anyone else find this?

 

I used the screw from my existing hop up unit to twist in and create my own threading. Unfortunately I've now snapped the screw itself! Anyone know where I can get a replacement screw? I think I will have to drill the snapped end off somehow...

 

Anyone with suggestions would be great!

 

Thanks.