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Old August 21st, 2008, 19:27   #100
mcguyver
 
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Join Date: Aug 2005
Location: Northern Alberta
I have a fix for PTWs with hop-ups that seem to not work (ie adjustment does nothing). The 2007 and back guns use a square o-ring to seal the barrel to the chamber. When you insert the barrel during assembly, significant force is required. It's easy to over-shoot the barrel key guides, and a natural response is to just pull the barrel back a bit and insert the barrel key. What ends up happening is that the chamber is not as smooth as the barrel, so you end up over-inserteing that square o-ring.When you pull back on the barrel, the o-ring remains in place and squashes against the adjuster. It provides enough friction that the cushions can't overcome it, and your hop-up is essentially fixed in place. If you try to screw the adjuster up, you end up deforming it slightly, and the roller cants to one side a little (and this causes problems).

I've noticed this on my own back-up M4, and a local fellow who bought a used PTW had this issue at a game on Saturday. I think alot of guys who complain about lack of range or ineffective hop-up may have this problem. For 2008 guns, Systema uses a smaller round o-ring to do the job. Likely, it was a problem for them during assembly as well, as it requires probably 50+ pounds of force to insert that barrel, and it's real easy to over-shoot the key guides.

I'll take some pics later and show you what I mean.
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