Hide glue is, indeed, a great glue for furniture, veneer, and musical instrument making. I am currently using it to construct a violin right now. But I would NEVER be tempted to use it on a firearm of any kind. In instrument making, you want a very strong joint, but one that can be easily and cleanly disassembled should the need arise. This is easily done with a little warm water at the joint. Hide glue does have a very short working time depending on working conditions, and about a 24 hour cure time, again, depending on environmental conditions. On top of that, hide glue must be kept between 145 and 160 degrees F in a glue pot, and it's consistency constantly monitored due to evaporation that occurs as the minutes pass.
However, a firearm is likely to see water in it's lifetime, so a waterproof glue is called for here. I have been using Titebond Ultimate for any wood repairs on the rifles I build, as it claims to be water-proof.