A Comancheros bikie who smashed a man's hand with a sledgehammer will remain in jail after pleading guilty to blackmailing another small-time drug dealer, saying the man was in direct competition with the motorcycle gang.

Alex Bourne, 30, appeared in the ACT Supreme Court today on charges relating to incidents from December 2016.

The court heard Bourne was a member of the Canberra chapter of the Comancheros motorcycle gang and that his role within the group was as a standover man who collected debts for drug trafficking.

Court documents showed in December Bourne discovered that a 20-year-old man was selling small quantities of MDMA to his close friends.

Bourne went to the man's house and told him he had put himself in direct competition with the Comancheros' drug dealing and was "putting a dint in their wallets".

Bourne told the man he had been planning to "tie him up, put a gun in his mouth and then shoot him", but decided against that course because of CCTV cameras at the premises.

Bourne instead demanded cash from the man, who paid Bourne almost $10,000.

Days later another man contacted the dealer over the encrypted messaging system Wickr and demanded $15,000.

"Hey mate, you lied to us. You better give us $15K by 9:00pm tonight otherwise you've started a war you cannot finish," the message read.

Bourne then followed up with the dealer saying, "If ur not going to pay thats fine ill go away and let the river run its course".

He warned the dealer if he went to police "there [would] be consequences".

Bourne later supplied the man with nearly 50 grams of MDMA, which he told him to sell in order to make the money back.

Sledgehammer used to crush ice dealer's hand

In a separate incident before the court today, Bourne also pleaded guilty to intentionally inflicting grievous bodily harm to another drug dealer, who had sold the drug ice in the Comancheros' territory.

The court heard Bourne used a sledgehammer to smash the man's hand several times.

The man suffered several fractures and the second strike caused the bone on the top of the victim's hand to protrude.

The court heard his middle finger may yet need to be amputated.

Bourne will be sentenced in February and will remain on remand in prison until then.