Puzzled over my ICS Sig 551 miss feeding?
 

Just recently purchased an ICS Sig 552...not new but used.
Anyway, the problem is that it shoots 10ft and also jams. When I shoot upside down it shoots great, sometimes a double BB in full auto. The minute I right it up again and shoot, same thing, it only spits out the BB. I'm puzzled and any advice and help would be appreciated.

Sounds like the hop-up is dialed full on. Make sure it's off. Failing that, make sure the rubber isn't damaged.

Yeah I checked the hop up, is was dialled all the way down and its a new rubber bucking. still puzzled as too why its doing this.

Is something loose inside? If turning it upside-down rectifies the problem, a part may be out of sync. I can't think of anything else if the hop is tuned.

Or maybe the BB's aren't going far up enough into the barrel and are hitting the side when being blown by the piston, and turning the gun upside-down helps them chamber properly.

My two guesses. :\

This would have been useful information to include in your OP ;)

Along with JLiang's post, nozzel to hopup misalignment would be my next guess. Check both for signs of impact. Does it have an aftermarket hop-up unit? I had one gun that misfed and double-fed like a bitch on an aftermarket hopup. It did the same after I installed a tightbore in the OEM hop-up.

Also, just a random possibility, have you tried different BBs and different brand of mags? Long shot but I've seen problems caused by mags or BBs that a gun for some reason takes a disliking too.

That's also a possibility. Some BB's are, for example, 5.95 mm in diameter, while others are 5.8 (REALLY crappy ones I saw at a dollar store once. It actually said "5.8mm BB Pelats" In that exact wording. :P ), and even others, 5.99 mm. BB to BB differentiation occurs, too, but as you said that you did this multiple times, I'd assume that's not the culprit.

Also, are you using Mid/LoCaps or HiCaps? Sometimes, guns have a preference on mags, too.

Alrighty, I'll check all your advice and possibilities and let you guys know. I don't think its an Aftermath Sig (jing gong) because I tried to replace it with one and it doesn't even fit. And Kalnaren, sorry I didn't state all my variables.

what bbs are you using? have you tried different brands?

maybe its the mag? weak mag spring not pushing bbs up? or its binding in the mag?

Yeah this one is a real puzzle.
Tried different BB's ( Ksc, elite,
Tried different mags ( TM and Mag brands - Hicap and Midcap )
Tried different bucking, shredder, nub. hop up is dialled all the way DOWN
Tried new barrel tight bore
Tried looking down the the BB well and the nozzle goes all the way back, I can drop one BB in it and it shoots perfectly upside down!
Could it be the previous owner put in the wrong nozzle?
I don't know how that would effect it upside down. Help, whimper.

SIG thread!?

What brand of magazine is this problem occurring with?

both Tokyo marui Midcap and MAG brand Midcap, and both of them work perfectly in my friends ICS SIG 552.

I had similar problem. In my case it was the screws that attached the grip to the mechbox, had become a bit loose inside. So sometimes the motor wouldn't engage fully, causing misfeeds, and double feeds.

Take your hopup unit out, and look from the back (or where the bb enters), it should be a nice and round opening... if its a little oval, then that might be the cause of your misfeeding!

Had the same problem with my SRC hk416 and same symptoms back in the days, thats because aftermarket hopup rubbers are packaged in small bags and get squished , making them oval... :S

BTW: does semi auto work?

Might also be a work out tappet plate, or the nozzle not sealing properly with the hopup rubber....

I would think so ^

the main causes of this problem originate from:
Air nozzle (too short or too long)
Hop up Bucking A.K.A. rubber (is shredded deformed or ripped)
hop up chamber
Magazine not providing enough umf to get the bb into the chamber properly...

other than that i would take a look at your tappet plate just to be sure.