Re: 2 + grains over book max?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: p25</div><div class="ubbcode-body">I did not mean to offend you armorpl8, but you are either missing my point or I am not explaining it very well. When the writers of whatever book you are using compiles their data, how are they getting it and what exactly is max value?
1) Is max value the velocity because that is where they begin to see pressure issues or achieve the max chamber pressure on whatever guage they are using? In other words do they figure that this velocity will most likely be the highest achievable with safe pressure?
2) Is max value the powder charge that they found gave the max pressure on a gauge or showed danger signs? Or possibly they deem this to be the max powder charge that will produce safe pressures? The corresponding velocity happens to be what they achieved with the powder charge that they deemed to be safe.
Maybe this is a chicken and egg question, I don't know. That is why I am asking. I am just trying to understand the relationship between velocity and pressure and how it relates to book max. Should velocity be considered the max? Work carfully up from there if you choose to do so? Or should the listed max powder charge be considered max? Or is there a happy medium somewhere? I fully understand that every difference in what they are using and what I am using makes a difference. I certainly don't want to ruin my equipment or myself.
Think about it this way. Which is more important to approach or exceed with caution, velocity or charge weight? Maybe both, I don't know, that is why I am asking. </div></div>
You did not offend me at all, I am not a teacher so I don't have much patience
If you have never read your loading manual please do so from cover to cover. Most, like Sierra, have a great deal of valuable technical info. I reccomend getting your hands on an old Lyman manual as well, there is some very useful information in a Lyman manual besides the actual loads.
1) I think I understand. You want to know how do they come up with these arbitrary numbers in a manual? Well many different companies have all kinds of equipment and not all use the same methods. Some use pressure barrels and when the load gets to SAAMI max(a PSI standard determined for a certain cartridge, 30-30 is lower number than the 223, has nothing to do with cartridge capacity) then that is max. Sometimes they use a regular rifle just like you buy in the store and I can only assume that they use many of the same methods we use to come to their conclusion. In this scenario I can see how the data will seem conservative, and it may well be sometimes. Much of the data is based on the yeild strength of brass. Again not all brass is created equal some brands can be stronger than others but all may vary lot to lot. I think I actually may have covered both 1) and 2). The velocity is what it is, yes, when they get to max by whatever they deem that to be, by the methods they are using, the velocity is what it is, period.
I tell you what you can do. Read all you can on "case head expansion". This is one of the most definative ways to see if you are in danger of blowing a case. If your case head expands .0001" measured at a very distict point on your case then you need to back off. If any part of the head of your brass begins to "flow" it has been exposed to at or near its yield strength, just that simple. One thing I definately agree with Clark on here is that many should stick to the book and do it by the book.
I have loaded for many wildcats over the years, and still do, where there was little to no data available. Yes I have "winged it", but I had a lot of normal experience and many hours of reading under my belt before I was ready to play outside the box.
Between a friend and myself we have 3, 6BR custom XP100 pistols. All 3 wear 15 inch barrels and were cut with the same reamer. We shoot nothing but Varget and either 105Amax or 107SMK and all 3 guns have a different max load. Somewhere around .5 grain between them. This should illustrate why you must be very careful beyond the posted norm. Just make sur you know exactly what you are doing and what Newton's laws apply.
