Quoted: I was wondering if the threads on a lower are the same between manufactorers so that the buffer tube will screw in the same distance on a CMT vs a Noveske vs a Mega and so on? The reason I ask is that I had a bushmaster and a mega lower and the 6 position stock would collapse tight against the castle nut.  Now I have a Noveske which I am told was made by CMT and I believe a CMT stock kit and i cannot get it to screw in enough so that the stock is tight. So is it that the reciever threads are different and dont allow it to go far enough in or is it that the buffer tube is longer?  Ive looked a the picture threads and all the 6 position stocks I saw collapse very nicely against the castle nut. I would like to keep my reciever and stock but wouldnt care much if I had to get a new tube or something.  Any help would be great

I think your poll is invalid.  I dont know of any spec that states what the distance between the stock body and the castle nut should be.  Nor does it matter.  At all.

This goes far beyond the threads of the lower.

To answer the question - yes, all lowers are cut the same... as far as thread pitch goes.

The collapsing stock is designed so that you can thread the tube in just until it retains the buffer stop.  Then, the castle nut is installed, tightened, and the body is installed on the buffer tube.  The body should be able to open and close, and be able to firmly click into each position.  If your stock doesnt do that, something is out of spec.  

The above could be caused by a WIDE range of things:

Stock body too long.
Buffer tube stop holes drilled incorrectly
Buffer tube threaded in too far
Castle nut too wide
receiver out of spec in dimensions
receiver out of spec in the location of the buffer stop hole
carbine plate too thick

Depending on the lower receiver and buffer tube... sometimes a tube will barely retain the buffer stop, but when threaded in another revolution, it is too far and hitting the buffer retainer.  The best thing a manufacturer would do is grab another tube from the pile.  For the avg home builder, it isnt all that uncommon to have to remove a little material from the bottom lip of the tube to keep it from hitting the buffer stop detent.  However, being one whole revolution further in will put the stock body closer to the castle nut.  Just how it works.  These are mass produced interchangeable parts built to a spec.  Sometimes, with the concept of tolerance stacking... these things can happen.

That said - my carbine's stock bodies range from 1/8" to 3/16" of gap off the nut when fully closed.

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Quoted: I also needed to shorten the overall length of my ar to fit in my SUV cargo box and cannot find a larger version that would work for me so I had to make it fit and making my buffer tube go in farther would accomplish this for me.   Last night I just needed to get it done and took a chop saw to my buffer tube.  I shortened it about 1/4" and that was perfect in that it allows the stock to fully collapse and got rid of all the exposed threads.  Also fits in my lockbox.   So unless I hurt anything by chopping off 1/4" of the tube(I made sure the threads were ok and everything went back together nicely) then I am good to go

Check on two things.
First, is the overall length legal?

Second, does the bolt catch operate properly?
Generally, you need about 1/4" of travel past the bolt catch for the bolt catch to pop-up and stop the bolt when the magazine is empty.
If you don't have at least 1/8" to 3/16" of extra travel, the bolt carrier/buffer will not dwell at the rear of the tube long enough for this to happen.

You can take the buffer out and shave off the end of the elastomer snubber until you get it working again.