It only happens sometimes. In order to create a reliable repair record for a firearm, one must provide enough information to safely reproduce the event. This can be quite difficult for an intermittent firearm fault. The first person to describe the event in adequate detail will greatly affect the subsequent examinations of the same problem.
Do not attempt to diagnose what might be causing the problem. Create a reliable account of what you have observed. Describe what happened and under what circumstances. If something changed later then describe that too. The owner and the gunsmith must be able to rely on your history of previous repairs to the firearm. If you are unsure about anything then say so.
Start with the observable symptom
Just describe the event and don't try to assign a cause. For example: "The slide stopped out of battery" describes an event, but "The extractor is broken" would be a diagnosis of the cause of the event. The problem is that the same symptom can have many different causes. For example: Ammunition, Fouling, Worn parts, Timing problem, Parts not fitting together properly, Unusual interaction between parts.
Please use the same words the owner would use to describe a problem with their firearm. For example, instead of saying "it didn't fire", say "the trigger didn't reset" or "the gun didn't go bang". Owners can provide a great deal of information regarding a problem without having to understand the technical terminology of a gunsmith. The owner should give as much detail as possible regarding what happened, what they saw, what they heard, and what they felt, and indicate which information they are certain of and which they are only guessing.
If the firearm developed a potentially dangerous sign such as an unusual sound, weakened shot, cracked part, bulge, leaking gas or a gunned round that did not exit the barrel then cease all use immediately. Seek the advice of a qualified gunsmith.
Give the fault a timeline
List the occurrences with the date and time of each in as much detail as you can recall. If possible, list the number of occurrences in each session. Note whether the problem appeared at the start of a shooting session or after a while and if it ceased at the end of the session or continued for the remainder of the shooting session. List any events that may have occurred between each occurrence, i.e. was the rifle cleaned, was it left in a storage place, was different ammunition used, etc.
If a problem occurs more than once, it would be good to record how many times it occurs. It's also good to note how the problem ceased to occur – did you finish the session, did you use up a batch of ammunition, did the gun cool down, or did the problem just stop happening?
Do not use a single occasion when the gun fired properly to state that the problem has gone away. Absence of symptoms is evidence but not necessarily cause. Record in repair history each time that the gun is fired and for how long in each occasion, even if no problem occurs.
Separate conditions from conclusions
You should list the conditions under which you observed the symptom in your note. These conditions can then be supported by your claim. List the conditions for the firearm (preferably model specific, including all calibers/chamberings the model was made in). List the ammunition(s) that you were using, and state whether they came from the same package each time. There can be huge variations between different packages of the same ammunition.
A description of the circumstances surrounding the event is also required. This includes details of the surrounding environment as well as any subsequent maintenance or part change. The aim of this is to assist the diagnosing gunsmith in identifying possible causes by outlining the circumstances that have changed between events.
An event that affected operation is best recorded using normal ammunition terminology (i.e. 'trigger does not reset' or 'extractor fails to remove cases' etc.). A description of what happened including any sight, sound or feel which the user experienced is also useful. The user must note whether they are absolutely certain that what they describe happened or whether it is merely their impression.
Preserve the physical evidence
Rather than test a fault for example by shooting and reloaded for testing it is better to store the firearm and have the firearm inspected by a gunsmith as soon as possible. So for example rather than cycling the action to test for a worn extractor ensure all parts including any magazines etc. are in their original condition as when first noted with any damaged cartridges etc. left in place.
Store the gun safely and note local regulations with respect to the safe transport of firearms. Even when seeking advice on potential danger, don't hesitate to ask the qualified gunsmith for further information on how best to transport your Firearms for service or repair.
While photographs of parts or damaged ammunition can be useful to record the appearance of components and the condition of used cartridges, they must not be used as a substitute for safe handling and inspection by a qualified professional. Record where components etc. were found and keep packaging etc. for damaged parts together.
Treat repair history as evidence, not folklore
While gun talk often gets passed down from generation to generation as folklore, as much as we would like it to be true, it remains unverified until documented. So ask the collector the following: 1. Was this EVER documented? 2. Did the collector personally observe this? 3. Did the previous owner ever comment on this? (And was this EVER written down?).
Invoices, notes from previous gunsmiths, parts lists, and old photographs all count as useful evidence. The fact that a part was replaced is useful evidence but it does not provide any evidence of why it was replaced. Nor does it provide any evidence as to whether the same problem has reappeared.
These items will likely affect how a collection item is characterized, even if only for a short period of time. The best description of historical repairs and other work done to a firearm is the evidence itself, as opposed to some unverified story that may or may not be entirely accurate.
Ask for a diagnostic conversation
When at the gunsmith's workshop explaining the problem to him first write down the most repeatable symptom of the problem and then give him a chronological account of all the events and include all relevant documentation. It would also be very helpful to inform him about failures and about instances where the problem occurred as well as about instances where it did not.
Useful questions for the gunsmith to consider would include: 1) What evidence would be required for the gunsmith to consider disassembling the firearm in the first place? 2) How would you distinguish between problems caused by ammunition, and problems caused by mechanical faults?3) How would you establish that continued safe use of a firearm would not pose a risk to the user or others? The answers to these three questions, and the subsequent repair, should be fully recorded, including the originally reported symptom, the confirmed cause(s) of the symptom(s), and the full work carried out to rectify the problem(s).
Marking the observed symptom(s), confirmed cause(s) and completed work in separate areas of the work order creates the best future evidence even for the most intermittent problems. All too often an item is brought in for repair that has already acquired a 'reputation'. Verification or otherwise of a single examination is rarely sufficient to confirm or otherwise such widely held beliefs.