NRA Journal - Spring 2007 - National Rifle Association

length of the chamber. In the classical bottle-neckrifle cartridge, it is the length of the gap between thebase of the cartridge, or the belt in the case of beltedcartridges, and a point on the shoulder. If the chamberis too long or the cartridge is resized too much, thenthe brass will have to stretch each time on firing andwill eventually weaken at the base. This can oftenbe preceded by a bright ring seen around the base ofthe case just up from the web. If you see this, throwaway the whole batch of brass as it is about to let go.normal conditions but appearing to be OK and thenfiring this apparently safe load after the rounds havebeen left in direct hot sun.Is there a problem with old brass? Not necessarily,but I have recently seen old (10+ years) factory loadedammunition that when fired holes appeared in the caseallowing gas to escape. It had clearly corroded fromthe inside and so the problem was invisible until itwas too late. Likewise with primers; old primers canpierce when fired. This has happened recently so, themoral really is don’t use old components.Case showing a split around thebase just above the web.Old factory loaded case withsplit allowing gas to escape onfiring.All primers are equal; not so. Although there is theobvious difference between standard and magnumlarge rifle primers there is also a difference betweenprimers of different manufacturers. Some are definitely‘hotter’ than others and this will affect pressure andvelocity. There was an interesting experiment todemonstrate this a few years ago by Mik McPhersonin the USA. He produced a cartridge case base thatcould have primers inserted and fired, but the rest ofthe case was missing. He fired each primer in the darkand photographed the resulting flash, and there weremarked differences in the intensity of the flash whichhe surmised would translate to the rate at which thepowder was ignited in a normal load. As ever, thiswill probably not make a big difference with mildloads but if your loads are nearer the ‘hotter’ endof the spectrum then a change of primer may wellmake a notable difference to the result of pulling thetrigger. Will it cause catastrophic failure? In itselfalmost certainly not, but this is as good a place asany to point out that most handloaders do not do anyone thing rash enough to blow up a rifle. Problemsusually occur when there are a number of factorswhich in themselves are not extreme but by bad luckor the sheer determination of the handloader to pushall the limits, they add together in a concatenationof events resulting in a major problem. A typicalexample would be everything on the limits underPropellant: this is where the gremlins have the bestchance to get to work. The choice of powders is hugeand the burning rates vary enormously. Even differentbatches of the same powder may vary, so it is wise tocheck when starting a new batch. No-one deliberatelyloads pistol powder in a rifle cartridge but it hashappened. What it boils down to is if the burningrate and amount of powder loaded into a case are notappropriate for the case capacity, the calibre of theround and the weight of bullet, then things are going togo wrong. Either too much or too little pressure. Theonly person who should be determining the choice ofpowder and the load you use (remember it’s your headnext to the controlled explosion) is you. Informationis readily available from the manuals provided by thepropellant manufacturers and will give safe startingloads. The place not to go for information is someoneon the range who tells you to use x grains of y powder.He may know what he is doing but he may be usingmuch lighter bullets for example. Even worse is thegenerous person who provides you with some of hishandloads. These might (but how do you know?)be fine in his rifle but there is no certainty that theywill be OK in yours. I was present some years agowhen someone in my club shot the revolver he hadpurchased from an acquaintance (I hope it was not afriend) who had also kindly provided some loaded26