Let us start with the barrel. I am discussing Precision Rifle Series (PRS) type shooting, focusing on centrefire. It is very important to have an exact round count on the barrel. How many rounds have you shot through the barrel? I am going to say, in short: Some barrels are shot out at 1 000 rounds if not cleaned and maintained correctly.
Calibres like 22-250-6 mm Creedmoor and 243 Win can have a very short barrel life. There are various reasons. If maintained correctly, a 22-250, 6 cm, 243 Win will give you 1 800 to 2 000 competitive shots. You will be able to push it to 3 000. But that is more for hunting / plinking. A 6.5 calibre will give you 2 500 to 3 000 competition rounds and a 223 Rem. 308 Win 3 000 to 4 000 rounds.
So, getting the rifle ready for a competition. I cleanI use a bore scope to determine if the barrel is clean of carbon. Check just behind the case neck for any carbon build-up, the dreaded carbon ring that affects accuracy. Make sure to clean the neck area at the throat and the chamber. Check for carbon five to eight inches down the barrel. It will ease off towards the crown from there.
