Thanks everybody for your input.
My worry was that the shorts' rims would be sitting at the back end of the cylinder's chambers, but the actual (shorter than usual) bullets would be farther away from the barrel entrance itself and would travel a few millimeters in the cylinder before entering the barrel (possibility of slight tumbling?) while for the regular 22 LRs, the chambered bullet is practically kissing the barrel.
Noise is really a secondary item. I shoot at a range and ear protection is always ON.
What I'm doing is
a) breaking in my Heritage Rough Rider .22 LR 6.5" barrel
b) breaking in my GSG 1911 HV (I won't even try lowe velocity ammo in it)
After firing a few hundred rounds through each and boresighting my metal sights,
I will then try shooting a variety of the different .22cals LRs and try to find out
which ammo is liked by each gun.