"Any magazine, belt, drum, feed strip, or similar device that can hold more than 10 rounds of ammunition. One exception to this is a magazine that was manufactured before September 13, 1994. Another exception is an "attached tubular device designed to accept, and capable of operating only with .22 caliber rimfire ammunition". This means a tube similar to the magazine on a shotgun but on a .22 rimfire firearm."
We all know this.
My question is, is there a standard "ammunition" that is used to measure cartridge size? For example:
My Mossberg 590 is chambered for 2 3/4" and 3" Shotgun shells. It holds 8+1, 2 3/4" shells, or around 6+1, 3" shells. Fantastic. HOWEVER, Aguila makes short slugs. Like, 1" slugs. If those were used then I have a device that can hold 14+ shots. Wtf?
This springs to mind because of the thread about the .50 Beowulf in .223 mags. In that case the mag can hold 10 .50s, or the standard .30 .223s.
I'm assuming this is going to end up with another "NYS is stupid and this is a gray area" answer, but damn, things like this REALLY need to be thought of before laws are made.