Compression with new hopup and barrel

thedudeofsis · 06-29-2010, 05:57 PM

I just recently switched my m4 to a metal body and therefore needed to change to a single piece hop up. I also took this opportunity to change to a 6.01mm tight bore. My problem is that I get maybe three good shots off with the range I would expect with this setup then everything goes to hell and the bb's are dropping out about 15 yards away.

When the shots are good the gun sounds like it normally does, but when it starts to fire poorly it gets much louder and sounds sharper. I've already tore down the gearbox to check everything and it seems to all be in working order. Also hop up has been turned all the way off so that's not a problem either.

There is too much of a coincidence after replacing the barrel and hop up for this to be a gearbox problem especially after I checked it out myself. So the question is why am I loosing so much pressure with the new hop up and barrel? Any help is appreciated thanks.

**Bracket** · 06-29-2010, 09:34 PM

I got the Madbull 3-in-1 chamber thing, because I liked the dial, and it did the same thing. The dimensions on that thing just aren't right. If that's the chamber you got, I'd reckon that's the problem.

And yes, it's definitely a barrel problem, not a mechbox problem. Check to see that everything's seated right, and that the bucking isn't bunched up anywhere. Also, make sure the barrel is clean and you're using good BBs, because there's not a lot of room in 6.01 barrels.

thedudeofsis · 06-30-2010, 06:57 PM

As an update I switched back to my old hop up and everything works dandy now. I'd leave it as is but with the current hop up I cant use the metal body I bought. SO as it stands there is clearly a problem with the new hop up and it meshing with the tappet nozzle. Any more help would continued to be appreciated.

thedudeofsis · 07-03-2010, 01:26 PM

I've been able to narrow down the issue a little further.

As stated in the above posts, I have disassembled the gearbox and everything in there is in fine shape. It is not an internal gearbox problem. Also since I've switched back to my previous old hopup while still using the 6.01 tightbore I have had no problems firing the gun, therefore the bb's are not an issue.

When I had the new hopup on the tightbore I could cover holes and blow into them and get really good pressure going. Therefore it is not a problem with the seal between the new hopup and barrel.

The new hopup is fully pressed backup against the gearbox so nothing I can improve on there, there's just physically no way to move it back further.

Since I switched back to the old hopup while using the same barrel and gearbox and have seen a vast improvement in performance the issue has to lie with either the seal between the hopup and gearbox/nozzle, or there is a problem in the way the hopup/nozzle is feeding the bb's to the chamber.

Knowing that it is one of these two problems narrows it down considerably. I just don't know how to go about testing for either possibility, or if I do find out it is one or the other I have no idea what to do to fix it.

Again thank you all for your help and suggestions.