Tried a new Titan 10" upper on my m16 and it ran great, 800 rounds and no issue except that my mag kept dropping out.
It doesn't drop mags with a M4 barrel.
Thinking the shorter barrel hits back harder.  I put a toothpick in the side of the mag release button and they did not drop.
The short barrels must shake things up a bit more shaping up the loose mag release button.  
But I love the Titan upper!  the fit and finish was much better than what I expected.
I will try a new button spring.  I was wondering if anyone had this issue with a shorter upper.

Thx
J

What lower do you have?

Olympic  PAWS

Think the hard kick could possibly damage the M16 lower??

I changed out the mag catch parts with FN AR15 parts.  The FN spring was about 1/5th longer.
I was going to try it and see if it works.  Then thinking I am ok?    I dont want to damage the M16 lower.

Normaly its the slot for mag catch is not deep enough, one easy way is to ben the mag catch. Ill send you one thats bent and ugly but works. I just milled the slot .005 at a time till a mil. Spec catch locked good on all mags.