TM FN57, Outer barrel/O Ring/wayward shots

[Asomodai]

Hey all.

 

Picked up an aftermarket outer barrel for the FN57 which is supposed to stop the Hop unit and such from wearing out. I fitted the barrel and test fired at 5 metres and seemed fine.

 

I immediately took it to Cornwall and I am here for the next few months with no tools, (though I still have the original outer barrel with me).

 

I took it to a game day today and noticed the O-Ring that is on the Outer Barrel to prevent the recoil spring and stopper from falling off had broken in half and fell out. 

 

When firing the pistol about a third of the shots immediately fire a good 5-10 degrees to the left and then curve around to the right. Some shots have too much hop and the rest not enough.

 

Now considering I have no tools, what is the most likely culprit?

 

The new outer barrel?

The missing O ring which is there specifically to stop the recoil spring going too far forward and going missing when disassembling? (it may have a secondary barrel stabilising function, but I can't prove that without a working O ring)

Something else?

 

Here are photos of the new outer barrel and the old one. 

 

New

 

Old 

 

Any idea what size O ring the stock one is?

 

 

 

Edited August 22, 2021 by Asomodai

[Adolf Hamster]

sounds like the ob has become misaligned and is catching bb's on their way out.

 

similar effect with a wobbly suppressor.