Barrel Life: A Screed of Old Standby & the Math of the Matter By Meccastreisand
When you talk about “barrel life”, exactly what you are talking about is of paramount importance but isn’t clarified by the simple words “barrel life”. To some people it means the time when the gun is no longer safe to fire. To others it’s the period of time when the barrel is still able to do its job even if a bit poorly. Still others are concerned with some characteristic of how it shoots i.e. consistency of accuracy, velocity, etc… Some of us are very intolerant of a barrel being even just a little long in the tooth while others don’t really care as long as it holds together during firing. Well that complicates defining what a barrel life is now does’t it? How can one discuss anything without a basis of understanding with their audience? So, let’s just chat a bit and at the end you’ll find a very useful gift.
Figure 1. Black powder guns need cleaned promptly to prevent serious rusting. .45-70 Sharps 500gn LRN
What affects barrel life is an easier thing to discuss than how long an actual barrel WILL last. Simple things like rate of fire, bullet construction, powder burn temperature, case:bore capacity ratio, rifling design are going to affect the average rifle a heck of a lot. Some of these are worse than others naturally and some can be made much worse by silliness. Complicated things like chemistry and the intersection of chemical and physical processes, things like simple cleaning, also dramatically affect barrel life.
Figure 2. Magnum revolver forcing cones often experience erosion. Wonder why? .357 magnum WW 110gn
The long and short of it is, anything that applies heat or friction and many things in the way of cleaning agents/chemicals are only going to add to the wear. Anything that happens while there’s fire present is likely to be able to have fast and very severe effects compared to things that don’t involve fire. Even the most aggressive chemicals that can harm your bore, when used incorrectly take a while (numbers of minutes or hours) to do much serious damage. With fire, it’s frequently right away that the damage is done and it gets worse with each shot that happens before things have cooled. Shoot your rifle fast till it’s hot to the touch and you’re burning the barrel and shortening its life in a dramatic way. You could even burn that throat out in one bench session if you’re too zealous. Ammo doesn’t come with a shots-per-second recommendation. Ask me how I know.
Figure 3. 19th Century Cannon Rifling. There’s a bit of erosion.
Chemistry. I love chemistry. Why? It’s unforgiving. Leave ammonia based copper remover in your bore too long, you’ll chemically damage it. Longer exposure with chemicals is generally always worse. Thankfully it’s pretty uncommon for shooters to improperly use really nasty chemicals on their gun. RTFM right? You can tell a nasty chemical most of the time by the smell. Folks tend to whiff a funny smell just go back and RTFM if they hadn’t before. Apart from the fact that there is a label with information on the subject to read, stink motivates curiosity.
Figure 4. Tight SD's are hard to get from a worn out barrel.
To dive deeper into the discussion we’ll use a single definition of “barrel life”. It’s not valid for all discussions but it’s the way this one is being framed. For the purposes of this essay a barrel is at the end of its life when it is no longer able to provide the accuracy, reliability, safety or consistency that its use case requires. There. That’s nice and broad.
Barrels have a life in rifles because: rifling and fire. Rifling has an origin and a terminus. Conventional rifling impresses ridges into the sides of the bullet. This is literally scraping one kind of metal against another hard enough to cause a deformation in surface profile of the softer one. Add doing this under extreme pressure and temperature and you have just defined an extreme wear area. Most guns chambered for bottle necked cases will wear the throat first by a long way. Why? Well they’re overbore. More powder than pipe so to speak. That’s also where pressure differentials are at their highest and where there’s a change in the surface profile from flat and smooth to having distinct ridges impressing themselves into the bullet.
Figure 5. That's five miles of gravel road right there.