I created a Data Base using note books, for each rifle. In that Data Base I enter all the information of the days shoot. On the computer I have a file for each rifle. In that file I add a picture of the target from each shoot. On the picture I am always care to include date, time, weather, powder charge, distance, and projectiles. Again this is another point of reference. I can then search the Data Base by rifle, projectiles, just about anything and it will give the the shooting results from each rifle and a picture of how the rifle performed.
That also helps when I get another rifle. I can search caliber, twist, etc and I have a pretty good idea of how the new rifle might shoot and what will shoot best out of it.
And yes, that is only part of the collection. I have a real problem when it comes to muzzleloaders. I keep telling myself that I will not get another, but then I find one on an auction site and next thing you know, I own that one also...