Anyone running a 7in barrel on their ar15?

[tp555]

I have made a short barrel in 9mm for a customer that cycles with factory ammo.Barrel is 10" using the gas system.The gas tube is about 3 inches long and straight.Spring is normal but buffer is 9 oz.Just to see how much umph it has.Blank is special tight bore in 9mm.With heavy spring and 9 oz buffer it cycles with can but not without it.So how far can you go? You need custom gas block and short gas tube.Barrel nut was different.