Systema PTW MAX Problems (chewing bbs)

[colonel_kipper]

Hi,
I've been having serious problems getting a SCK PTW max to work with any chamber consistently. The problems are as follows :
Feeding was erratic, but that was solved by realigning the inner barrel.
Now it feeds, but most shots either are split into pieces, jam, fire straight for fifty yards or come out at incredible angles (60 degree divergence from the barrel at 20 or 30 yards). I've tried new cylinders, many types of bbs (currently using excel .2s) and lubricating every part and ensuring smooth operation. I can't figure this one out at all. Any help would be very much appreciated.
Cheers.
Ed.

[MadMax]

Are your mags engaged very tightly in the receiver? Do you have to slam them on the bottom to get the catch to engage the retention window at the top of the mag?

Clear all bb fragments between tests. Bits of busted bbs can cause jamming and complicate diagnosis.

[colonel_kipper]

Hi Madmax,
yeah, the mags do seem to be very snug, and require quite a lot of effort to seat. I considered getting some wet and dry sandpaper (fine grit) and just taking off a little bit of material from the inside of the receiver, but I wanted to be sure it wasn't the fact that the chamber assembly/hop unit was misaligned.
Ed.

[Kokanee]

I suggest trying a different brand of BBs. When I built my SCK last year, I was using excels and guarders in my other AEGs and found that they produced the same problems in my PTW as you are having.

I found that BB Bastard brand ammo works flawlessly, as it's a much higher quality bb than excel. The PTW is really quite picky about the quality of ammo you feed it.

Oh damn, just noticed you're in the UK... Hmm I'd suggest heading on over to the systema europe forums @ http://www.systema-ptw.com/forum/default.asp

And asking what BBs avail in the UK feed well w/ the PTW.

[MadMax]

Originally Posted by colonel_kipper

Hi Madmax,
yeah, the mags do seem to be very snug, and require quite a lot of effort to seat. I considered getting some wet and dry sandpaper (fine grit) and just taking off a little bit of material from the inside of the receiver, but I wanted to be sure it wasn't the fact that the chamber assembly/hop unit was misaligned.
Ed.

Well, this raises some concerns. Mag fitment is probably the most likely cause of your feeding issues. You shouldn't just dive in and start doing irreversible material removal though.

I would like to try a simple test before proposing an adjustment.

-Remove your hop up assembly and barrel
-stuff mags into receiver

If you have difficulties pushing mags into the receiver until the catch engages the mags and this difficulty disappears when you remove the hop up assembly, then I suspect that either the assembly is not aligned correctly or your mag catch needs resurfacing.

I have seen a lot of PTW M4's which required resurfacing of the top engagement surface of the mag catch. They cranked the mags too high in the receiver which caused the top of the mag to press too firmly against the hop up. The mags would roll clockwise (gun pointed to the right) as the rear top corner of the mag was pulled up at the engagement window. This would cause inconsistent feeding at the retention fingers at the top front of the mag and result in half fed balls that got chopped.

Also check your mags for bb debris. If your mags are contaminated with bb bits or dust, pellets can jam in them and cause half feeds.