I'm curious...would it be NJ legal if all of the receiver extension adjustment holes (accept for the one that the stock is set on) were filled with JB Weld?

Only if the untouched one is the closest to the receiver, because any other would allow the stock to collapse.

Just get a Magpul MOE fixed carbine stock or a Strike Industries fixed Carbine Stock or one of the many fixed stocks that are available.

no need to fill receiver extension/buffer tube holes.

NJ does not say anything about permanently fixing a stock, does not give an outline on whats acceptable. just says basically cant have a folding or telescoping stock. this has been
on going since ive been into the AR platform in NJ. But you do not need to make anything permanent.

drill and pop a roll pin in it to stop it from" telescoping" or use a range roll stock lok kit, they fit most stocks. now its not telescoping

can that be changed with tools, yep. so can the barrel length, auto sear, muzzle device and everything else. heck it can even take a standard capacity mag with out any modification.(just saying)

If they wanted something more it should be outlined, I don't believe there has ever been a case where someone was brought to court over a stock

get the stock you want, modify the stock, dont mess with the buffer tube and you will be fine. YMMV

Thanks for the replies.

I found these shortly after my original post and ordered one from primary arms...

https://www.aimsportsinc.com/amp/stock-locking-pin-for-magpul-stock/