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Reloading Basics: Fine Tuning

Reloading Basics: Fine Tuning

Anyone new to reloading will know that making and firing your very first batch of homemade ammunition is very satisfying. Hopefully, the rounds perform well and the results on the target are good. It will, however, not be long before you start questioning if you can make it perform better and what ‘tweaks’ you can make to your rounds. This curiosity will typically last the whole of your reloading career and it is what makes this one of the most interesting aspects of the hobby, welcome to the world of ‘load development’.

Establishing a baseline

There are several simple things you can change with your reloads, to see how they affect accuracy and performance; but first, it is important to establish a baseline, using your loads for a while and keeping a record of the results. Once you have sighted your gun in, using your reloads, keep the targets as a record of the group size to compare to the results you get from any different reloads you make. You should also keep a note of things like felt recoil and any feed problems that you may experience with your loads, as these are also aspects of the ammunition’s performance that you can tweak during load development. Make a dummy round of your baseline ammunition and mark all the dies, so that you can return to the baseline setting at any time.

Making a change

It is very important to only tweak one thing at a time, otherwise it is impossible to identify which of the changes you have made is responsible for the impact on the way the ammunition performs. The easiest variable to change is, of course, the powder charge weight and, assuming you have followed the instructions with the reloading data and started well below the maximum, there will be room for you to change the amount of powder you use, without exceeding the safe limit.

The cartridge Overall Length (COL) can also be changed within a usually small range and this will have a direct effect on both chamber pressure and headspace, both of which can impact of accuracy.

The amount of crimp you apply to your rounds is also an easy thing to change and this has a surprising affect on the performance of your ammunition. It can also change the way your rounds feed, depending on the type of ammunition and feed system of the gun.

Powder charge

Most powder manufacturers will recommend a starting load of 10% less than their published data and then working up and watching for signs of excessive pressure. If you have followed this advice, and it is very foolish not to, then you can carefully and very gradually increase your powder charge towards the maximum and see if it improves accuracy.

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Alternatively, what you can also do is gradually reduce the powder charge in a similar way, to see if accuracy improves. Reducing the amount of powder that you use will also reduce felt recoil, which may well help improve accuracy, by making the rounds more comfortable to shoot. If you are shooting at say 100-yards, for accuracy, there is no point in using ammunition that generates so much recoil that you flinch each time you pull the trigger.

Reducing the powder charge will also make your ammunition cheaper to make; the smaller the charge, the more charges you will get from a tub of powder. You must, of course, be careful not to reduce the powder charge too much, or you may well see rounds passing through the target sideways, a sure sign that your bullets are not stabilising in flight. Very usefully, a lot of powder manufacturers produce data with a ‘starting load’, which you can pretty much regard as a minimum powder charge for load development purposes. It is important to remember that a small increase in the powder charge can generate a disproportionately large increase in pressure; a five percent increase in the powder charge, in a typical .308 Winchester load, generates a seventeen percent increase in pressure.

Cartridge Overall Length

Cartridge Overall Length is a critical dimension, as it sets both the amount of bullet protrusion and the amount of useable space within the cartridge. Generally, in handgun calibres, the COL should not be reduced below the recommended figure, because the resultant increase in chamber pressure can be significant. With rifle cartridges, there is a little more leeway in terms of COL and it can be fine tuned to suit the particular rifle. Where powder manufacturers, for example Alliant, publish a minimum COL, it is unwise to go below the stated figure.


In very simple terms, you can think of crimp as the amount of ‘grip’ the case has on the bullet. The tighter the grip, the more force is needed for the bullet to break free. The force is produced by the pressure generated by the powder burning inside the case. By varying the amount of crimp, you are directly affecting the pressure required to start the bullet on its journey up the barrel and this has a surprising effect on the accuracy of your ammunition.

As with the other reloading elements, you can change there are limits inside which you have to operate in terms of crimp. Too little crimp and you risk not ‘resizing’ your finished ammunition, so you might have problems with chambering rounds. You also risk the bullet not being held securely and it can move into or out of the case while it is being handled or chambered. Too much crimp can damage the bullet, cause rounds that headspace on the case mouth to not chamber properly and generate too much pressure inside the case on firing.

When you are adjusting the crimp and using a die that both seats the bullet and crimps the case, take care not to change the COL at the same time. Dies of this type require the bullet seater plug to be backed out by the same amount that the crimp part of the die is screwed down.


Staying within the safe limits, you will find that small changes to powder charge, COL and crimp will have an effect on the point of impact and group size on the target. Making up small batches of different loads, labelling them properly and keeping records of the results will enable you to get the very best out of your reloads. Most importantly, stay within the limits stated in the reloading data you are using, this will ensure you and your gun stay healthy!


Henry Krank & Co Ltd. henrykrank.com
Norman Clark Gunsmiths. normanclarkgunsmith.co.uk
JMS Arms. jmsarms.com
1967 Spud Reloading Supplies. 1967spud.com
Hannam’s Reloading Ltd. hannamsreloading.com


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