#required libs and tools:
sudo aptitude install libghc-opengl-dev libghc-sdl-dev make -y
 
#http://sourceforge.net/projects/prboom/files/prboom%20stable/2.5.0/
wget "http://colocrossing.dl.sourceforge.net/project/prboom-plus/prboom-plus/2.5.1.3/prboom-plus-2.5.1.3.tar.gz"
tar -xvf prboom-plus-2.5.1.3.tar.gz
cd prboom-plus-2.5.1.3
./configure

#change how much AMMO is used in each shot
vim +746 src/p_pspr.c

#change how many pellets are used in each shot
vim +752 src/p_pspr.c

#Change Vertical Spread of pellets
#angle += (t - P_Random(pr_shotgun))<<19; //original
#angle += (t - P_Random(pr_shotgun))<<21; //Full Screen
vim +758 src/p_pspr.c

#Change Horizontal spread of pellets.
#((t - P_Random(pr_shotgun))<<8), damage); // 8 is about full width
vim +761 src/p_pspr.c