Help! Mossberg 590 Shockwave Forend

[Kooenaybackwoods]

I recently picked up a Mossberg shockwave with the 14 inch barrel. I was trying to install a magpul forend, a very simple and popular upgrade. Unfortunately the castle nut that hold the forend on would not budge. I have the correct metal tool to unscrew it and it is so stuck that now it is just spinning the metal tube Inside the hand guard. The action tube assembly is what most call it. Maybe the nut was cross threaded?
Has anyone experienced this? What can I do now?

 

[call2arms]

sounds like you are unscrewing the magazine tube from the receiver

 

[Kooenaybackwoods]

No I'm not, the action slide tube assembly slides on the mag tube.

 

[jetfixer]

If I understand - this is what has happened:

If you are able to pull the slide tube off, you will then have to take trigger assembly off so you can slide out the action bars. I don't have my 590 in front of me right now so I can't see if it would be repairable, but the pins holding the action bars to the slide are sheared, they need replacement or you may need to get a new slide assembly. The nut may have been cross threaded or water got in there and corrosion has occurred.

 

[Kooenaybackwoods]

Thanks! Very helpful. Unfortunately action slide tube are sold out everywhere right now...Hopefully I can track one down.

 

[jetfixer]

I took my forend off and realized the tube is flared, as in the picture. No sliding it off forward. I think you will have to take the trigger assembly off so you can pull the whole pump assembly off. You may be successfull by clamping the tube to the action bar brace on two sides, while being carefull not to warp the tube, spray lube on the threaded area and try taking the end cap off. Cutting the forend off might be a last resort so you can clamp the entire tube in a vise (a wood dowel of the same inside diameter being placed inside the tube would minimize deformation) and try to remove it. You can try heat if you have that option. If you notice whiter granules in the thread area, its a sign of aluminium corrosion.

 

[Kooenaybackwoods]

Appreciate your advice and taking the time.
I took the whole pump assembly off, tried putting it in the vice in different configurations but still no luck. It still functions as is so I don't want to cut the plastic off. I think I will try to track down a new assembly and just live with the current state.