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UKCYukarin

Off spec lower reciever or off spec V2 gearbox?

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Hello,

So basically the original gearbox of my gun shat itself and so i went to replace it. I bought a NUPROL rear wired v2 gearbox, and well, the gearbox won't fit into the receiver.

The rear portion of the receiver is too big at the back (where the buffer tube screws on) marked by the area that I filled in attempt to fit the gearbox in.

 

Anyway, I can't tell for the life of me tell if the Lower Receiver is off-spec or the gearbox is offspec. Looking online at other gearboxes, my gearbox looks like the shape as others. The same can be said with my current lower receiver.

I no longer have the original gearbox to compare but from memory it looked like a standard V2 gearbox.

 

Need to know if I have to replace the Lower Receiver or the gearbox (again!) in order to fit this in.

Base gun is an Arcturus AR15. Gearbox is a NUPROL Delta V2 rear wired gearbox.

 

Thanks

gearboxrecieverproblems.png

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That should fit? Can you put the box in the receiver and take a photo of the issue... I have a feeling I might know but want to be sure!

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Unfortunately I'm away for a few days and can't take another photo of the gearbox inside the shell. Ill post an image as soon as I can but for now ill describe the problem as best i can.

Putting in the gearbox into the receiver, the front end of the gearbox (towards the hop up) fits in fine. As well as the width of the gearbox. The problem that is stopping the gearbox from fitting in is the metal part below where the buffer tube screws in. (the part with exposed metal on the pic). It blocks the gearbox from sitting in properly at the rear.  The gearbox sits in such a way in that it slopes down towards the front.

Sorry if the description is awful, i'll upload a pic asap.

Thanks for your help!

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Its the full-length AR15 Carbine model. Thanks for finding that image, very useful! Clearly my google skills suck.

Welp, looks like ill have to buy a new Lower, which might mean my upper may not fit and so on, plus ill need a new buffer tube as the AR15 uses a Milspec Buffertube.

This gun has been nothing but work 😫

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Might be worth emailing either Nuprol or Arcturus... Hell, contact PB or another retailer, they may give you a straight answer from their own tech experience.

 

If you still have the busted box, lay it and the new one side by side and have a nose at the variation.

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I bought this gun from PB a while back and had it sent back in because the Quick Change spring system on the original gearbox didn't work, they were pretty stumped. I think that article you linked gave me a definite answer in that the receiver is off-spec due to the off-spec gearbox (or vice versa). Going to replace the lower, which is a shame because its so nicely made.

Anyway, thanks again.

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