A Ministry of Defence witness should explain its disclosure of files to an inquest into a loyalist shooting, a family lawyer said.
Ballistics experts are working to establish whether the weapon used to kill a Catholic salesman more than 40 years ago can be linked to other murders.
Daniel Carson (29), from Dunmurry, was gunned down by the UVF as he left work at a hardware merchants in the Shankill area of Belfast in November 1973.
During a previous hearing, the coroner Mr Justice Adrian Colton described the Ministry of Defence's (MoD) inability to track down a former lance corporal who attended the scene as "baffling".
Family barrister Karen Quinlivan QC said: "We maintain our application that a witness for the MoD be called to explain the position on disclosure.
"The MoD have indicated a resistance to that."
The coroner said he was generally sympathetic to that approach.
"If someone has first hand knowledge of the steps that are taken it can be helpful," he said.
He told family members who attended the Belfast preliminary hearing that a significant amount of work had been done since the last time lawyers met.
"These hearings are important to make sure that the work is continuing in the case.
"You may think that this is a routine matter, it is not. It is important that we maintain the work that is being done.
"All the lawyers in the case have their shoulders to the wheel."
A fresh inquest into the sectarian shooting was ordered by Northern Ireland's Attorney General.
No-one has ever been convicted of Mr Carson's murder.
But a man who was arrested and interviewed about the shooting is to be legally represented at the inquest. He was detained four days after the murder and released without charge, the court heard.
A barrister has been enlisted and his instructing solicitor said he hoped progress would be made early in the new year.
