Hope it turns out a great event mate!
We have a similar event here for our Big Game Rifle competitions - 'Rook & Rabbit'.

ROOK and RABBIT RIFLE
a. Muzzleloaders and cartridges introduced before 1905
b. Muzzle energy not to exceed 400 ft lbs. Muzzleloaders to use a max.
powder charge equal to caliber e.g. .45 cal = 45gns max.
c. Plain base lead bullets only – round lead ball for muzzleloaders only
d. Cartridge rifles to have been made before 1940.
e. Muzzleloaders are to be of pre 20th Century styling.
f. No bolt actions or semi-automatics
g. No telescopic sights
h. No target rifles
i. To include 25/20 and 32/20 using plain base lead load
j. Excluding .22 Rimfire.
k. One target per distance
FIRING SEQUENCE
Rook and Rabbit Rifle (20 shots)
50metres/yards - 5 shots off hand (5 minutes)
- 5 shots sitting/kneeling (5 minutes)
25 metres/yards - 5 shots off hand (5 minutes)
- 5 x 1 shot in 3 seconds per shot off hand.