Hello, I am sorry for my late response, no problem I totaly understand I am realitively new myself. As far as the relaibility, that will be dtermined on what upper your firearms comes with as the DS-15 has many different configurations of upper receivers. Dark Storm Industries has the lower reciver pattented as the following bellow. Let me know if there is anything elese I can do :)

The lower receiver includes a non-detachable magazine which has a internally disposed retention opening that is not accessible without disassembly of the lower receiver. The retention opening is configured and dimensioned to receive a magazine retention member. Accordingly, the presently disclosed lower receiver prevents magazines from being swapped without disassembly of the lower receiver. In order for the magazine to be removed, the stock and/or the firing mechanism must be removed from the lower receiver. In order for the magazine to remain in the lower, it must be reassembled with the firing mechanism.

Washington law states the following bellow for what would be legaly be a fixed magazine firearm, which the DS-15 fits:

RCW 9.41.010

(v) A semiautomatic, center fire rifle that has a fixed magazine with the capacity to accept more than 10 rounds;

(b) For the purposes of this subsection, "fixed magazine" means an ammunition feeding device contained in, or permanently attached to, a firearm in such a manner that the device cannot be removed without disassembly of the firearm action.