Police received reports relating to seven incidents in the Weavers Grange area of Newtownards.
Detective Inspector Corrigan said: “I want to reassure the community that we are treating these incidents, reported over a five-month period, extremely seriously and we are actively pursuing the perpetrators through our robust investigation with forensic analysis of these items ongoing.
“By setting these cartridges at the doors of these properties, this is a clear attempt to intimidate and exert control over others through threats.
“There has been enough unrest in this area and this must stop. Our district officers work tirelessly every day to protect communities and will continue with a visible presence in the area.
“Everyone has the right to live free from such threats and I would appeal to the community to assist our ongoing investigation.
“Anyone with information are asked to contact police on 101 quoting reference number 946 20/02/24, you can also submit a report online using the non-emergency reporting form via www.psni.police.uk/makeareport or information can also be provided to Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org.”
Last year, the estate was at the centre of a loyalist paramilitary feud sparked in March when the South East Antrim UDA said they had expelled members living in Newtownards.
The move left those members without the support of the paramilitary group, but the deposed loyalists refused to leave, saying they would be operating as the Real UFF.
The gang had clashed with a rival UDA faction and homes and businesses were attacked.
Local people say the gang manipulated the housing system, sending fake death threats to gain intimidation points and push them to the top of the list so they would be allocated homes in the newly-built estate.
Around 30 families fled the area during the feuding, with an almost constant police presence for weeks on end.
In April around 50 people took South East Antrim UDA murals down from walls in the estate.
A number of people have been charged in connection with the gathering, while local women also organised street protests demanding those involved in criminality leave the area.
Senior judge Mark Hamill was also targeted, his name painted alongside crosshairs on the exterior wall of Newtownards Courthouse where cases against the rival gangs were being heard.
Last October, an attempt to allocate some of the empty houses in Weavers Grange to families on the housing list was abandoned after threatening graffiti appeared on the walls of the empty homes.
Clanmil Housing Association, who own the estate, initiated legal action against two individuals — linked by police to the feud — for breach of their tenancy agreements.
Those orders were granted and the two tenants given six weeks to vacate the properties. The orders were enforced in November 2023.