Try make this gun:
[Motor
nickname = missilemy_motor
lifetime = 0.200000
accel = -3530.038601
delay = 0.2

[Explosion
nickname = missilemy_explosion
effect = no_capgun01_flash
lifetime = 0.000000, 0.000000
process = disappear
strength = 300
radius = 50
hull_damage = 500
energy_damage = 500
impulse = 0

[Munition
nickname = missilemy_ammo
explosion_arch = missilemy_explosion
loot_appearance = ammo_crate
units_per_container = 10
hp_type = hp_gun
requires_ammo = false
hit_pts = 2
one_shot_sound = fire_missile_regular
detonation_dist = 4
lifetime = 63.750000
Motor = missilemy_motor
force_gun_ori = false
const_effect = gf_co_smallengine01_fire
HP_trail_parent = HPExhaust
seeker = LOCK
time_to_lock = 0
seeker_range = 1000
seeker_fov_deg = 0
max_angular_velocity = 0.000000
DA_archetype = equipment\models\weapons\li_rad_missile.3db
material_library = equipment\models\li_equip.mat
mass = 1
volume = 0.000000
linear_drag = 50.000000

[Gun
nickname = missilemy
DA_archetype = equipment\models\weapons\li_rad_launcher.cmp
material_library = equipment\models\li_equip.mat
HP_child = HPConnect
hit_pts = 400
explosion_resistance = 1.000000
debris_type = debris_normal
parent_impulse = 20
child_impulse = 80
volume = 0.000000
mass = 10
hp_gun_type = hp_gun_special_1
damage_per_fire = 0
power_usage = 0
refire_delay = 0.1
muzzle_velocity = 700.299999
toughness = 0.400000
projectile_archetype = missilemy_ammo
dry_fire_sound = fire_dry
separation_explosion = sever_debris
auto_turret = true
turn_rate = 90
lootable = true
LODranges = 0, 20, 60, 100