Hmm. Good thought. That drastically narrows the field, though. The ones that have the magazine either in the grip or behind it for maximum compactness are:Put the magazine in the grip just like the pistol it pairs to.
- Roni conversion (Are they still in business?),
- MechTech conversion,
- Beretta CX-4,
- Hi-Point Carbine,
- Kel-Tec Sub-2000,
- Tavor Bullpup, and
- Calico Carbine (Definitely no longer made.).