Caliber Performance vs. Barrel Life Economics: There is no such thing as a free lunch. When selecting a caliber it is an easy thing to jump right on the hottest ticket that launches super-high-BC bullets at just less than the speed of light. Cartridges which have the number 284 or the words Mag, Ultra, Laz or STW in their names fit into this category. You may ask, Whats not to love, especially if I am going to hand-load to cut down ammo cost? Besides, Joe Super-shooter just won the ________ (fill in the blanks with Leech Cup, F-class comp, 1,000 yard National Benchrest, or killed a trophy unicorn at 1,200 yards or something...). Maybe you heard some secret squirrel military unit is testing it for viability. (Wish I had a buck for every time Ive heard that. :) ) OK. Well enough. But how does that relate to what YOU are doing with it? The hot ticket calibers eat barrels. Period. It is one of those very inconvenient laws of physics that says larger case volume to bore-size ratios and steep shoulders require slower powders, higher temps and pressures and as a result eat out throats quicker. What the budget-minded precision rifle fan must understand, is that the big guys that use and win with those calibers are often sponsored shooters who dont buy barrels or get them at reduced cost so they arent paying full-boat for a new tube every 1,000 to 1,500 rounds. If they are paying for them, (at $500-$700 a pop) they must by doing well in life. Kudos. I am a firm believer that the barrel manufacturers are the biggest proponents of hot calibers for obvious reasons. Nothing wrong with that, its just good business! ;) You cannot however, overlook the bottom line of barrel life and replacement costs which should help guide you in your caliber choices. Which brings us to the issue of how many rounds you expect to get out of yours, for your purposes... The reason someone builds a precision rifle is that they have an expectation or NEED for accuracy beyond that of the common rifles and factory hunting / plinking ammo fodder they can pick up at Walmart. There is a certain standard they wish to achieve in terms of accuracy. Sometimes this is a pre-decided standard, but sometimes it is a nebulous As good as it will shoot sort of thing. At any rate, there is a certain amount of fiddling around that usually occurs before the standard is either achieved or more often, accepted. How long this takes depends on the standard and the anal nature of the rifles owner. Just remember that the lifespan of the barrel begins its countdown with the first round fired. And Brother, do the rounds add up fast! The Cumulative Math: Zeroing: The new barrel will need to be put on paper and a rough zero established before load testing can be done. A skilled shooter should be able to hit paper and make a bold adjustment on round 1 or 2, and use a 10 shot statistical zero to wire it tight. Add 12 shots. Break-in: Some will engage in the dubious exercise known as Barrel-break-in to start the barrel wear process by fire-lapping the bore. Based on the method followed it will take 50 to 100 shots. We will assume the low end number of 50. Round count 62. Despite their higher quality, not many precision rifles or barrels will like every ammunition you toss into the chamber. There is a certain amount of ammo you will need to test, either by sampling factory loads or doing hand-load development. Factory ammo: Considering that you need to shoot a minimum of 20 rounds of a selected ammunition to be able to assess how well it groups in a given rifle; AND that most folks will shoot a minimum of 5- 7 different loads before they have found The One, you may add another 100-140 rounds if you are not indecisive. We will arbitrarily say 120 as an average. Get a little crazy and it could easily be 200. For arguments sake, we will say 160. 160 + 62 = 222. Hand-loading: This is where it is very easy to go down the rabbit hole. Most precision hand-loaders will try at least two optimal bullets. Under these two bullets they will usually try at least two powders, sometimes 3. Most will do a ladder test to determine the optimal charge weight, requiring an average of 10 groups of five shots each over a 2 grain range. If only two powders are tried under each of the two bullets, at 50 rounds per powder type, 200 more rounds will have been fired. if three powders are used this increases to 300. Once an optimal charge weight has been identified another 20 rounds may be expended tweaking bullet seating depth. At this point we are at 220-320 additional rounds if you did not try any factory ammo. Again, we will split the difference and go with the median of 270 rounds. With the perfect load identified it is time for data collection. 270 + 62 = 332. Data collection: First we have to refine the zero for the selected best ammo before trajectory data can be collected. Add 10 rounds. We will assume that the shooter at this point has either used a chronograph during load development, or has an idea based on the reloading manuals of what the muzzle velocity may be. The approximate trajectory is dialed and groups fired at a middle distance such as 300 or 500 yards. The statistical center of a 10 shot group is measured and identified. This is compared to the ballistics program output. A second data point is found at a farther range (800 to 1000 yards) and the test repeated. if conditions are poor or if the shooter would like to be sure of this data, a second 10 shots train may be advisable at each of these distances. For confirming zero and data collection, add a minimum of 50 rounds. For those using the traditional KD range method of firing at 100 yard intervals to 1,000, you may add 100 additional rounds. We will assume a median of 75. 332+75 = 407 rounds. Shooter training: With the special load identified, the rifle zeroed and trajectory data collected, you may want some field practice with the rifle prior to your hunt, or want to train for the match which you hope to shoot. Lets assume you fire 2 strings from each of three alternate positions, and do have an afternoon of engaging some steel scattered at various distances until you feel confident in the rifle, load and dope. Add 120 rounds. 407 + 120 = 527 rounds. At this point you are ready to start doing some good work with the rifle. Except... Mission creep happens. You decide to change optics. You re-zero and take the new scope through a box tracking test. Add 30 rounds. 557 rounds. You decide that you want to use the rifle for another additional application, and want to use a different type of bullet for ________. You repeat the load development cycle and now have two primary rounds that you may use for different applications. 857 Rounds. You repeat the trajectory data collection cycle. 1127 Rounds. At this point if you have a caliber which has a short life span, you have already used a significant portion of your barrels life administratively just getting it ready to be applied in a real world application; whether that is sniping, match shooting, hunting or just long-range self entertainment. Some may already be shot out. For those still shooting, enjoy the high performance while it lasts because you only have a few hundred more rounds left before the register rings again, or you have to turn it in to your armorer to go back for a new barrel under the maintenance contract. On the opposite end of the scale are the calibers which are very Barrel friendly, but which offer less than stellar ballistics - calibers like the .308 which offer 6 to 8 times the barrel life of the hottest calibers. If you want a rifle to shoot a LOT, the .308 is your huckleberry. In the middle are some calibers like the 6.5 Creedmoor , .260 Rem and 7-08 which offer reasonable barrel life and good performance. I generally find these the best compromise if the rifle that does not need to deliver a large bullet for terminal effect. Bottom line: Every rifle or barrel purchase is a roll of the dice. That new tube may shoot great with the first load you put in it, or it may take a lot of rounds down range to find the special load. You mathematically increase your chances of having a lot of usable barrel life left by choosing a caliber which is easy on barrels and budget friendly to shoot unless you have a drop-dead requirement for the barrel-burner. At some point it is not even a matter of cost, so much as a matter of aggravation in replacing and tweaking new barrels and loads. Id rather be spending that time training the shooter (me).
Posted on: Sat, 22 Nov 2014 23:33:22 +0000
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