So it's legal to affix a collapsible stock to a post ban receiver as long as the stock is pinned in the open position.  Does the collapsible stock have to be pinned all the way open?  Or can it be pinned half open so my kid can use the rifle?

Tampa:  No.  It's legal to mount a stock that LOOKS like a collapsible stock, but doesn't collapse.  ATF has so far never approved a "non-collapsing collapsible" stock that was made from a real collapsing stock, for commercial production.

If you were to take a telestock and pin/epoxy it one position, that meets the letter of the law, but probably wouldn't be approved by the ATF tech branch for sale as a commercial product.

The position of the stock (open, closed, halfway) isn't important, as long as the rifle is still over 26" long when it's mounted - which it always will be on an AR with a 16" barrel.  A 16" barrel AR with a fully closed telestock, or fake telestock in the closed position is still 32.5" long.

Thanks circuits. Dang the government drives me crazy sometimes.

Dave don't be discouraged, just about every company makes a post ban CAR style stock now.
I just got off the phone with Bushmaster and they make an ATF legal non-collapable stock.
I think American spirit arms makes the least expensive ($69.95) go to there web site  do some research but as far as I know there all legal.   Good luck

just another idea here but i have seen telestocks pinned in the shortest position with a an ellongated recoil pad added for trigger pull. this would give you the shorty length for concealability (as long as it was still 26 inches) and you slip on your elongated recoil pad for shooting.