Way back around the turn of this decade I asked this very same question. Here is what Nicholas said:
Any form of burst or suppression fire takes one round.
In terms of the number of bullets/bolts required for a burst, for spread burst, you need a minimum of three bullets/bolts per target. For aimed burst, use the same unless the weapon is something like a revolver or some such where "burst fire" is actually representing a "double tap". Likewise for fully automatic weapons like machine guns, bursts may trivially go through tens of bullets.
The rules allow for finetuning, so GMs with a plethora of gun expertise can adjust the rate of ammunition to suit specific weapons. The weapons in the HARP SF core rules are deliberately generic. I fully expect that we will have a lot more detail in a future sourcebook or combat supplement.
So for my bughunters game I built my own rate of fire tables.
Item
Avail
Cost
Mass
Att size/type
fumble
Burst bonus
recoil pen
RI
PB bonus
PB range
SS/burst/supp
shots
TZ-37 Stun Pistol
U
300
0.5
sm neuro
01-02
10
0
10m
10
5m
1/2/3
20
M34A5 Heavy Pistol
U
700
1.5/2.5
md balistic
01
20
-15
10m
10
5m
1/2/3
12
H&K 86 Sm Pistol
U
100
0.5
sm ballistic
01-02
20
-10
10m
10
5m
1/2/3
17
Taurus 12mm Caseless Heavy Pistol
U
150
1
md ballistic
01-02
0
0
10m
10
5m
1/2/3
5
M181 Tranquilizer rifle
U
700
2.5
tiny puncture
01
0
0
40m
15
20m
1/0/0
1
M275 Assault rifle
R
800
3.5/4.5
sm puncture
01
30
-10
40m
20
20m
1/8/50
200
M138 Assault rifle
R
500
5/7
lg ballistic
01
20
-15
50m
20
25m
1/2/9
30
M507 Grenade launcher
R
350
3
mk2 grnd
01-03
0
0
30m
20
15m
1/0/0
1
HI-700-1 "Flyswatter" Autoshotgun
R
450
5
lg shrapnel
01-03
30
-15
10m
20
5m
1/3/6
18
HF-18 Flamer rifle
R
1200
5
md plasma
01-04
25
-15
10m
30
5m
1/3/6
20
M333 Howler Machine gun
R
1500
10/15
lg ballistic
01-03
50
-30
60m
50
30m
1/50/250
2000
M702 "Deadeye" Laser Sniper Rifle
U
700
7
md laser
01-02
0
0
60m
20
30m
1/0/0
100
M702-A1 "Deadeye 2" Laser Sniper Rifle
R
850
8
md laser
01-02
0
0
80m
20
40m
1/0/0
100
SU-8 Sentry Gun
R
3000
45
lg ballistic
01-03
50
-10
60m
50
30m
1/50/250
4000
M720 Disco Light laser sentry gun
R
4000
50
md laser
01-02
50
0
100m
50
50m
1/6/30
5000
RU-444 Portable Missile Launcher
R
1300
10/18
tn warhead
01-04
0
0
50m
10
25m
1/0/0
10
PRC-12 Machine Pistol
R/U
550
1.5
sm ballistic
01-02
30
-15
10m
10
5m
1/4/12
23
PRC-50 Assault Blaster
R
1200
4
md blaster
01-02
35
0
15m
30
7.5m
1/3/6
50
Voidcat model 3 Tazzim Assault Blaster
R
12000
4
md blaster
01
35
0
15m
30
7.5m
1/6/12
100
Formatting this table is a mess for this post and I don't have time right now but you can see it in the spoiler section above. The line formatted x/x/x is the Snapshot, Burst Fire, Suppression Fire rate of fire entries.
Regards,