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Rifles, Reloading, Optics, Equipment
Reloading
Info on Excessive Pressure Signs for those new to reloading.
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<blockquote data-quote="Mikecr" data-source="post: 2330767" data-attributes="member: 1521"><p>I'm skeptical of these ideas until separated as problems, pressure problems, and actual excess pressure.</p><p>The golden rule is to work up in load. As you do this, you can can see problems, then problems brought on with more pressure, then undeniable excess pressure for the system.</p><p></p><p>For instance, flattening primers can be expected with fire forming of new cases, because headspacing is high enough to cause it -regardless of load pressure. Cratering around the pin, that's a non-pressure problem. Bush the pin and it stops, regardless of pressure.</p><p>Even a pierced primer(unless at a pin crater) is typically a primer cup flaw. If it is caused by pressure, you'll have every sign that exists with it beforehand. Swiping expansion into ejection recess, and expanding extractor grooves are examples of pressure problems. The actual pressure may or may not be too high, but it is excessive for you. There is a difference still.</p><p>I don't have ejector recesses in my single shot bolts, so I wouldn't see this swiping, so I could miss an indication here of pressure -or softer brass alloy. But I know that while using soft Norma, I'll see signs before harder Lapua. And I'll see it elsewhere in my testing.</p><p>Extractor groove expansion is out of my knowledge/experience base. I don't measure there. Could be a good measure.</p><p>There is one thing for sure in all this: if you have excess pressure (that's too high), it's likely you'll see ALL of this, and hopefully it's not too late for you.</p><p></p><p>But as you work up in pressures, ultimately, you should have well grounded expectations. </p><p>A chronograph validates your expectations. Very important tool.</p><p>With any new chamber, or new load, I do pressure testing for what I call 'MyMax'.</p><p>This is a point where FL sizing would be req'd -of new brass (after a single firing).</p><p>What I do is spot measure my case weblines as I go up in load. The webline is a visible highest diameter point at the web area. It's not a standard datum on paper, as case webs vary with their build. Winchester webs for a given cartridge could extend higher or lower than Lapua's webs for the cartridge. The webline will not be a standard diameter to expect either, as our chambers are all different, and our barrels and actions are different.</p><p>Anyway, I'll see the webline rise a bit (maybe 1thou) to plateau, then at some point I'll see a step change upward (another 0.0005"). That's MyMax, a runaway condition that has so far correlated with just passing SAAMI max pressure as shown in QuickLoad.</p><p>This has been so consistent that I wonder if it matches SAAMI testing method. And of course the chrono has been validating what I'm seeing. I log MyMax, and load development stays below this.</p><p></p><p>I could have seen problems on the way up to that. If I did, I would stop. I would address it before going further.</p><p>It is possible, I see chatter of signs in forums, that your max pressure is lower than others or book.</p><p>Every time, this is the result of a bad plan in the build. Usually a poor cartridge chosen for intent, or the wrong chamber or action for it, or mismatched reloading plan.</p><p>An example situation that I followed closely, and addressed, is with builds in 26wssm. It has 'short' in it's name so people would build with short actions. But they were missing 'magnum' in it's name. So they would pressure out early, with apparent pressure problems, not because their pressures were high, but because they didn't have enough steel around the chamber for a magnum diameter cartridge.</p><p></p><p>Unless you pick a wrong powder, it's pretty hard to go over pressure (IMO). But it's easy to create 'problems' otherwise.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 2330767, member: 1521"] I'm skeptical of these ideas until separated as problems, pressure problems, and actual excess pressure. The golden rule is to work up in load. As you do this, you can can see problems, then problems brought on with more pressure, then undeniable excess pressure for the system. For instance, flattening primers can be expected with fire forming of new cases, because headspacing is high enough to cause it -regardless of load pressure. Cratering around the pin, that's a non-pressure problem. Bush the pin and it stops, regardless of pressure. Even a pierced primer(unless at a pin crater) is typically a primer cup flaw. If it is caused by pressure, you'll have every sign that exists with it beforehand. Swiping expansion into ejection recess, and expanding extractor grooves are examples of pressure problems. The actual pressure may or may not be too high, but it is excessive for you. There is a difference still. I don't have ejector recesses in my single shot bolts, so I wouldn't see this swiping, so I could miss an indication here of pressure -or softer brass alloy. But I know that while using soft Norma, I'll see signs before harder Lapua. And I'll see it elsewhere in my testing. Extractor groove expansion is out of my knowledge/experience base. I don't measure there. Could be a good measure. There is one thing for sure in all this: if you have excess pressure (that's too high), it's likely you'll see ALL of this, and hopefully it's not too late for you. But as you work up in pressures, ultimately, you should have well grounded expectations. A chronograph validates your expectations. Very important tool. With any new chamber, or new load, I do pressure testing for what I call 'MyMax'. This is a point where FL sizing would be req'd -of new brass (after a single firing). What I do is spot measure my case weblines as I go up in load. The webline is a visible highest diameter point at the web area. It's not a standard datum on paper, as case webs vary with their build. Winchester webs for a given cartridge could extend higher or lower than Lapua's webs for the cartridge. The webline will not be a standard diameter to expect either, as our chambers are all different, and our barrels and actions are different. Anyway, I'll see the webline rise a bit (maybe 1thou) to plateau, then at some point I'll see a step change upward (another 0.0005"). That's MyMax, a runaway condition that has so far correlated with just passing SAAMI max pressure as shown in QuickLoad. This has been so consistent that I wonder if it matches SAAMI testing method. And of course the chrono has been validating what I'm seeing. I log MyMax, and load development stays below this. I could have seen problems on the way up to that. If I did, I would stop. I would address it before going further. It is possible, I see chatter of signs in forums, that your max pressure is lower than others or book. Every time, this is the result of a bad plan in the build. Usually a poor cartridge chosen for intent, or the wrong chamber or action for it, or mismatched reloading plan. An example situation that I followed closely, and addressed, is with builds in 26wssm. It has 'short' in it's name so people would build with short actions. But they were missing 'magnum' in it's name. So they would pressure out early, with apparent pressure problems, not because their pressures were high, but because they didn't have enough steel around the chamber for a magnum diameter cartridge. Unless you pick a wrong powder, it's pretty hard to go over pressure (IMO). But it's easy to create 'problems' otherwise. [/QUOTE]
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