Here is an extract, paragraph 13 of a CONFIDENTIAL REPORT, confirming that both the Anschütz rifle owned by Ralph Bamber, and the Brno .22 bolt action rifle were found at the scene on the 7th August 1985
The extracted paragraph states "On the 15th May 1991, Mr Pargeter's rifle, together with the .22 semi automatic rifle found at the murder scene on the 7th August 1985, with spent cartridge cases and bullets from the murder scene were submitted to the Metropolitan Police Forensic Laboratory at Lambeth, with a request for tests to be carried out as set out in Laboratory Form No.1 as attached."
The above lists the items submitted, separating them with commas. The wording used is slightly imperfect - the word "together" is redundant. However, that seems to be because of poor sentence construction, rather than because the two rifles were found in the same place or on the same date. Unlike the semi-automatic rifle and the spent cartridge cases and bullets, the first item is given simply as "Mr Pargeter's rifle", and this is consistent with the writer assuming that this rifle wasn't found or seized at the scene. What seems to have been in the writer's mind is that these items are now (1991) being submitted together for specified testing, whereas this had not happened previously (i.e., in 1985).
The paragraph doesn't specifically exclude the possibility that Pargeter's rifle was at the murder scene on 7th August 1985, but it doesn't confirm it either.