Go to stevespages.com. He has, if you look well enough, a strand with pictures of blown primers, cases, and other items that you will want to see. It should help you. I was ther today after haveing a case seperated on me today.
A new and interesting one is miking the diameter of primers. If your headspace is OK, the growth in primer diameter should correlate with pressure for any given set of constant primer case conditions. The case is important because the shape of the primer pocket will affect the flow of the primer rearward, creating a small flange - this is the spot that increases in diameter. For an initial baseline, do some measurements of factory loads, and use the same brass and primer types for reloads.
Another excellent approach is the use of a chronograph. Try to achieve the same VELOCITY indicated for a specific load in a good manual using the same components. Once you achieve the same velocity, on a consistent basis, you will be very close to the listed pressure. I do this with every load I work up, and powder weight varaitions are significant from the manuals. The hard part is adjusting the manual's velocity expectation with YOUR barrel length. Don't try to duplicat the velocity from a longer bbl with a shorter one. I deduct velocity/100 for each inch in bbl length difference - for 3000 fps/100, deduct 30 fps for each inch you are shorter. For pistols, velocity/25 might work - for 1200 fps/25, deduct 48 fps per inch. Don't try to deal with length variations over 4 inches, and don't work from shorter to longer, ie, increase the manual velocity.
You can combine both approaches and develop your own primer diameter data, related to pressure, but ALWAYS trust the chronograph over the primer diameter. Never exceed max velocities, no matter what. If your velocity is 5% high, your pressure could be 10% over max! Conversely, if your primers are too big, but max velocity is not reached, assume that you are too hot.
Subjective pressure signs, such as primer flattening, head expansion, etc. really aren't very reliable.
For modern center-fire rifle loads in rifles such as the .30-'06 a method which gives safe results is to start with new virgin brass, and to take one case, with your loading tools to the range, and take that one case and reload it ten times to shoot your group, and see if you can detect any loosening of the primer pocket. If the primer still seats firmly after ten reloads, the load is safe.
If the primer pocket gradually loosens enough within ten reloads that you can easily push an unfired primer by hand, by pushing a case held in your fingers against a table top, without using a priming tool at all, then the load is too hot.
If the primer pocket is loose within 5 reloads it shouldn't take a rocket scientist to figure out something is wrong.
This method is not reliable for cartridges developing less than about 50,000 cup.
This is a good and reliable technique, as long as you pay close attention to the pressure it takes to seat the primer in the first place. I have had new brass that seated with light pressure, and would not use those in the test. It would be a simple matter to develop a seating guage for this purpose, if anyone wants to develop a new and useful tool.
The two best indicators of high pressure are hard bolt lift/sticky extraction and any sign of brass flowing into extractor cuts or ejector pin holes. Primers vary with hardness so their appearance is not consistant. Miking case heads is ok for those with experience with good mikes but "ANY" brass flowing toward the unsupported parts of the bolt face is a sure sign you are too hot.
It is true brass flowing is a clear indication of excess pressure; however, by the time you get that far you are WAY into the red zone. You have problems that should have been detected earlier with the micrometer, chronograph, or just plain common sense.
If you get that far, stop, be thankful that you aren't picking pieces of the gun out of your teeth, and figure out what went wrong!
If you are a handloader and you want to work near max velocities and pressures, you need a chronograph, PERIOD. Short of a strain guage, there is nothing that will tell you when your loads go over max pressure until you are WAY over.
For any given set of components Velocity = Pressure. If your manual indicates that 2750 fps with 4350 is 50,000 CUP the CHARGE of 4350 giving you 2750 fps is giving you 50,000 CUP in YOUR rifle (adjust for barrel length).
If you don't want to spend $89 on a chronograph, you are better off shooting slightly reduced loads.
I disagree on the rifle flying apart because pressures are so high at the sight of a little brass flowing. Slight brass flowing means generally you are at the 65,000 psi threshold most cartridge brass starts to flow. To load the hottest practical ammo reach this point and back off two grains. This is a practical maximum for that rifle. The chronographs are helpful but the load manuals are not loading in your rifle so you have to do the footwork. Incidently brass is the weakpoint, most rifle actions will handle more pressure than the brass can so it is the weak link.
I would have to disagree. I have read several articles in the past couple of years, by Jaimison in Shooting Times and Barsness in Rifle/Handloader, where they had either strain gages or professional labs test their handloads. Handloads that 'appeared' perfectly safe by traditional measures, proved in the neighborhood of 70,000 PSI, if I recall correctly.
If anyone is interested I'll try to find the magazine articles. Remember - that's no brass flowing, no cratered/pierced/blown primers, nothing out of the ordinary. So what pressure would they have to have to see brass move into the ejector cut in those examples?
It's entirely possible to have things like a sloppy chamber or too-soft lot of brass leave those signs, before you hit those sorts of pressures. In a modern bolt-action rifle, I agree, 65,000psi isn't going to blow it up unless there is some other defect. But.... I don't belive that it is a safe thing to say that you are for sure under 65,000 or even 70,000psi, just because the brass hasn't flowed.
And then there is the entire question of action type. With a bolt gun, they're pretty strong, but if you get brass flowing in a 94 Win, say your prayers......
I agree with MikeG, and have read the same Jamison article. I can easily get 3200 fps out of my 300 RUM with AA8700 and 220 gr bullets with NO signs of high pressure. This is 200 fps and 7000 psi to hot, even though it is 3 grs below max in the manual. The chrono does not lie.
Well yeah the lever actions are not in this play. But the fact is if there is no brass deformation in a strong bolt action along with easy extraction the load is safe. This works in fact and all rifles are not the same. I have never blown a primer and most often cratered primers are the result of loose fitting firing pins or bolt face roughness. Seldom is it that I end up more than 2 grains from handbook maximums anyway and generally go with the most accurate load. I have witnessed many factory loads that showed noticable brass flow though not dangerously so.
Ray, very interesting, Ken Waters has preached the gospel of measuring the pressure ring for many years. Now it looks like we have some additional research in that area.
One thing to consider in all of this debate is why we'd like the brass case to contain the powder gas. The obvious answer is so that the bullet gets propelled out of the end of the barrel, and the shooter doesn't get a face full of soot.
But it goes beyond that. Once upon a time, case failures were considered a routine thing, and guns were designed to handle the escaping gas at 50,000CUP or whatever pressure. Look that the 98 Mauser - the big shield on the back end of the bolt, for example. We know that if a case fails at 50,000CUP it shouldn't blow the rifle to bits.
Now some folks will look at the strength of the modern bolt action, and say, Hey, this thing can take XX,XXXXCUP more pressure so let's load it up. All is well and good till a case lets go. But did the pressure blow up the barrel - usually not. Often the bolt lugs are still intact. Yet the escaping powder gas split the action into pieces. That part of the action wasn't capable of handling powder gasses blowing back through it at ultra-high pressures, even though the rifle might have not shown any problems if the case did not rupture.
Take a careful look at pictures of rifle blowups and see what parts of the gun survived and what did not. It's obvious the damage that the escaping gas did, once you think about it. The rifle design could not handle a case failure at that pressure level.
The cautious reloader/wildcatter keeps their fingers intact!
Rick, didn't mean to pick on you or your response, hope you didn't take it that way. There are a lot of people reading these forums, from those who have never loaded a single round of ammo to those who have been in the industry for many years. So the policy of the forum is to always encourage safe reloading practices. Sometimes it means shooting down some old wive's tales that have continued through the years, but that's a good thing in that we have an opportunity to spread knowledge. So I'm genuinely glad you brought up the topic of brass deformation.
Pressure is a VEEERY inexact science as it depends on each individual gun. Primers blown, sticky extraction, etc..not reliable. I agree with MikeG 100%, a chrony is the only way to know and even then with a tight chamber and barrel you just might still be over. I have a Ruger M77MkII in .270 Win that tops out VERY quickly. I usually can't make the max in the nosler #5, but meets advertised velocities. (almost) I also have a Browning Medallion 7mm Rem Mag that will digest 69 gr. of RL-22 with a Sierra 150 HPBT Match and never hiccup. My opinion: Don't force a 30/06 to be a .300 mag, if you want a .300...buy one. I hear people brag about hot loads and such...not me...I work up for accuracy or advertised velocity, whichever comes first. just my 2cents.
Tactfully and responsibly put. I sort of dug my heels in as well, but its just because its a safety issue.
The real problem is that we have focused in on charge weight as the independent variable, instead of velocity. I am much better off knowing that 2800 fps is the max for an '06 using large rifle primers, H4350 and a Nosler 180BT, than I am with some charge weight that is supposed to give me that velocity. Once you narrow components down powder, primer, case and bullet, VELOCITY = PRESSURE for any practical barrel length.
Of course, this requires a chronograph, and adjustments for barrel length. I seat nearly all of my rifle loads to the lands, and achieve max velocities several grains short of max charge weight. Of course, these max velocities are adjusted for the difference between the barrel lengths.
As you know, chronographing is fun in its own right. Clubs and ranges should provide them free or for a small fee based on hourly use. Gunsmiths should offer this service as well. SAAMI and the NRA should endorse and encourage their use for reloading activities.
Loader, my 30-06 gets 2850 fps with a 180 grain Speer spitzer on top of 59 grains of H4831 using a CCI 250primer. Cases easily last ten firings, I get fine accuracy and smooth extraction. Seems your working at it backwards by picking an absolute velocity and calling that the pressure level that is safe. Simply put there are rifles out there that could show high pressure when pushing a 165 grain bullet at 2800 fps. That is almost like picking a point in outer space and shooting for it. Nothing replaces working up loads in individual rifles.
I did a bad job of explaining it, but i'm just doing it the way the labs do it when they work up the data for manuals in the first place. For them, pressure is the criterion. For the '06 its 50,000 CUP or 60,000 PSI (same thing, different metrics).
H4831 will push a 180 gr spitzer 2737 fps at only 46,600 CUP from a 26 inch bbl, and your load is probably a tad over 52,000 CUP - quite safe for the '06 in any strong action. Your brass should be, and obviously is, just fine.
However, the charges that deliver 2850 fps will vary from 57 to 63 grains of H4831 in different rifles and chambers. This variation shows up in the various manuals when you compare them. I'm just saying that any charge of H4831 that gives a tad over 52,000 CUP in any of these rifles will deliver very close to 2850 fps in any of these rifles, including yours.
The correlation between pressure and velocity for a given powder is much higher than the correlation between charge weight and velocity across different rifles. If you know the velocity, you know a lot more about pressure than you can EVER tell by how the brass looks, or even measures.
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