USSR
Member
First, I will state that this is how I approach it, and it should only be done by experienced reloaders with the knowledge and equipment to do so safely. While this has worked well for me for a number of years, I accept no responsibility or liability for your load development.
Well, there are two types of Max loads. First, there are published Max loads, which are in fact not actual Max loads and vary according to the publisher's lawyers. And then there is the actual Max load for your particular rifle. If you are not an experienced reloader, then you should stay within the publisher's Max load data. However, if you are a reloader with the knowledge and suitable equipment to determine your rifle's Max load, then here is how I approach it with a modern bolt action rifle. First, you should have a chronograph, and have an idea as to what reasonable velocity you can expect from your platform (ie. boltgun vs. autoloader, barrel length, etc.) with a particular load. Second, you should be able to look at brass and see high pressure signs. The brass is the weak link in firing ammunition in any rifle, and will show signs of stress LONG before there is any danger to the structural integrity of the rifle itself. Always start out with a load well below the published Max load. You may not always be using the same brass or primer as was used in the reloading manual, so take that into consideration as well. I like to load 3 cartridges with a particular charge weight of powder, and then load several series of 3 cartridges with a slightly heavier charge weight, varying the charge weight of each series of 3 cartridges by 0.3 grains. At the range, you will start with the lightest charge weight cartridges and run them across the chronograph. Here is where you need to have an idea as to what maximum velocity is reasonable, and what is not. In a bolt action .308 Winchester with a 26" barrel, a 175gr or 178gr bullet can usually safely attain 2750fps with a suitable powder. If you reach that velocity without pressure signs, then don't push it. Now, what are the pressure signs. The first sign of pressure (both low and high) is transfered to the primer. With low and normal pressure, there will still be some "roundness" to the edge of the primer. Once you decide to run at a slightly higher pressure (but still within the SAAMI pressure specs), you will see flattened primers. While flattened primers are generally a sign of high pressure, they do not by themselves indicate that you are anywhere near the maximum pressure specified by SAAMI. Another sign commonly associated with high pressure is cratering of the primer around the firing pin indentation, although this can also be the result of an enlarged firing pin hole in the boltface. Basically, what I am saying here is, while you should take these signs into consideration, primers can and will lie to you. So, as you continue with the next series of cartridges (assuming you have no other signs and have not met the afore mentioned predetermined optimal velocity figure), the next two signs are what bring you to your particular rifle’s Max load, and cause you to stop further load development. Oh, and make sure you have a bullet puller, because you will have no doubt loaded a series of cartridges beyond this point. What will happen next is usually you will see a shiny mark on the headstamp of the brass. What this is is the brass is beginning to flow into the extractor hole in the boltface, and it gets shaved off as you turn the bolt to extract the case. If you see this, or if the bolt becomes hard to open to extract the case, then you have reached your particular rifle’s Max load and shooting should stop and all subsequent loads should be pulled. Any subsequent reloading using the same components should have a charge weight of at least 0.5gr – 1.0gr less than the load that showed high pressure signs. Using the above method, I have been able to obtain optimal performance for LR shooting, assuming I find an accuracy node in this pressure range. YMMV.
Don
Well, there are two types of Max loads. First, there are published Max loads, which are in fact not actual Max loads and vary according to the publisher's lawyers. And then there is the actual Max load for your particular rifle. If you are not an experienced reloader, then you should stay within the publisher's Max load data. However, if you are a reloader with the knowledge and suitable equipment to determine your rifle's Max load, then here is how I approach it with a modern bolt action rifle. First, you should have a chronograph, and have an idea as to what reasonable velocity you can expect from your platform (ie. boltgun vs. autoloader, barrel length, etc.) with a particular load. Second, you should be able to look at brass and see high pressure signs. The brass is the weak link in firing ammunition in any rifle, and will show signs of stress LONG before there is any danger to the structural integrity of the rifle itself. Always start out with a load well below the published Max load. You may not always be using the same brass or primer as was used in the reloading manual, so take that into consideration as well. I like to load 3 cartridges with a particular charge weight of powder, and then load several series of 3 cartridges with a slightly heavier charge weight, varying the charge weight of each series of 3 cartridges by 0.3 grains. At the range, you will start with the lightest charge weight cartridges and run them across the chronograph. Here is where you need to have an idea as to what maximum velocity is reasonable, and what is not. In a bolt action .308 Winchester with a 26" barrel, a 175gr or 178gr bullet can usually safely attain 2750fps with a suitable powder. If you reach that velocity without pressure signs, then don't push it. Now, what are the pressure signs. The first sign of pressure (both low and high) is transfered to the primer. With low and normal pressure, there will still be some "roundness" to the edge of the primer. Once you decide to run at a slightly higher pressure (but still within the SAAMI pressure specs), you will see flattened primers. While flattened primers are generally a sign of high pressure, they do not by themselves indicate that you are anywhere near the maximum pressure specified by SAAMI. Another sign commonly associated with high pressure is cratering of the primer around the firing pin indentation, although this can also be the result of an enlarged firing pin hole in the boltface. Basically, what I am saying here is, while you should take these signs into consideration, primers can and will lie to you. So, as you continue with the next series of cartridges (assuming you have no other signs and have not met the afore mentioned predetermined optimal velocity figure), the next two signs are what bring you to your particular rifle’s Max load, and cause you to stop further load development. Oh, and make sure you have a bullet puller, because you will have no doubt loaded a series of cartridges beyond this point. What will happen next is usually you will see a shiny mark on the headstamp of the brass. What this is is the brass is beginning to flow into the extractor hole in the boltface, and it gets shaved off as you turn the bolt to extract the case. If you see this, or if the bolt becomes hard to open to extract the case, then you have reached your particular rifle’s Max load and shooting should stop and all subsequent loads should be pulled. Any subsequent reloading using the same components should have a charge weight of at least 0.5gr – 1.0gr less than the load that showed high pressure signs. Using the above method, I have been able to obtain optimal performance for LR shooting, assuming I find an accuracy node in this pressure range. YMMV.
Don
