It really depends upon how the regulations are written, in implementing this law.
As it is worded, I can see a clear path that a detachable cylinder can be considered an "ammunition feeding device." For a non-detachable cylinder, I can see that a speed loader could also be considered as such.
For those of you that have M1's, make sure your stripper clips are 1 rnd short of full.
At least until the regs are actually written and you can see what is what.
The above is based solely upon how the actual wording of the law is and how courts have, by and large, interpreted those words. I am not an attorney nor am I a legal expert of any kind. So take what I have written with a large dose of salt.