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Multi-feed/low fps


Carta4
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Hi guys,

 

I recently acquired a CA stoner LMG. 

 

Im having problems when firing. The rifle spews out a few BB's a time at really low fps and more often than not there is quite a few BB's in the barrel after operation.

 

The hop unit etc seems in good condition (although I've got another lonex bucking and rubber ordered just in case). 

 

I have noticed that the nozzle tends to rest in a different place after every burst. Sometimes full forward, sometimes full back and sometimes in between. 

 

I'm wondering if this can cause the issue and if it is to do with the tappet plate/spring or if it's just normal on the CA stoner.

 

Any other reasons this could be happening?

 

Thanks!

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Well that's a relief that means leaving the gearbox alone for now. Yeh the feed lips looked a little suspect and the rubber was highly lubed so like I said I've ordered a lonex bucking and rubber. Hopefully that will sort it. Thanks for taking the time sp00n

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Unless someone has over lubed the cylinder and every time you pull the trigger it's spraying slippy gunk through the hop... ;)

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If you put a piece of paper or tissue over hop-up within the mag-well and it blew it out when fired, it means you have an air leak which will definitely be causing low fps.  This can be caused by numerous things, including leaks from the bucking, hop-up, cylinder, cylinder head, piston, piston head and air nozzle.

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The paper test will show up leaks between the nozzle and bucking. If you have a leak there and feeding issues check the alignment between the nozzle and hop /bucking /barrel. Pull the inner and hop out and peer down the outer barrel. The nozzle should be exactly in the centre.

Also check that the hop is actually pressing down on the bucking. With the inner and hop out of the gun wind some hop on and check you can actually see it protruding into the barrel. You should be able to put enough hop on to make it quite difficult to push a BB past.

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  • Supporters
14 minutes ago, Hangtight said:

You've certainly found one issue! Where there's one there's usually more...

 

Ain't that the truth!

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You're into the gearbox now, so you might as well do it properly. AOE, shimming, sorting out any other wear...

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Every time I've had a feed issue it's been related to the alignment of the hop and bucking with the air nozzle, but I'm unfamiliar with the arrangement in the Stoner. The usual one is the nozzle rubbing on the hop which restricts its movement. The spring isn't enough to pull it fully forward, although sometimes it'll unjam and fire a single round. Otherwise it's alignment front to back. Too far back and the nozzle can't pull far enough out of the hop to allow a BB to feed, too far forward and you don't get an air seal.

It's difficult to see as everything moves so quickly, but if you look down the feed nozzle into the hop does it look as if the air nozzle is travelling all the way forward into the hop?

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The stoner is very similar to the 249 if you have any idea on that? And I do believe the front to back is sound as it does pull back just enough to feed. It looks like it goes far enough forward but is there a way to make it go further? Also how would I lower the nozzle as it is a little high in the barrel so that could be causing and air seal issue.

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It looks as if the hop 'floats' and is located by the nozzle and the front of the gearbox, so alignment shouldn't be an issue unless the wiring has got jammed against it somewhere.

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It is a floating hop system, I think it's putting strain on the nozzle when installed as it sits slightly higher. I'm going to try and space the rear of the gear box so it sits properly. I'll let you know how it goes. Thanks again!

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