I have a 75 Shadow and an M&P 5 inch in 9mm. The M&P is faster by about 20 fps. The IDPA rules allow you to test your ammo against the longest barreled legal pistol in your division. Most likely the testers are using a 5 inch barrel or longer in the case of
the Glock 34. If you know your ammo passes PF with your M&P, take it to the match. If your ammo fails, you have the right to another test in the legal gun of your choice. Your Shadow does not have to make PF, as long as, another legal gun will. That is in IDPA. I do not know how USPSA treats this situation. Also, remember to raise the muzzle of your gun before each shot. I space that out periodically.