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You played a neat trick. You selected some of the low pressure old timers to skew the data. Go back and get the data for the highest pressure .30/06 based cases. Try the 25/06, 6mm Rem and the .270. You said the smaller case was safer. Do you still claim that? Assuming the action will hold a RUM size head at 65ksi the case is still the weak link now matter what sort of data torturing you do. A small case is not necessarily safer than a big case. | |||
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ireload2, please read my quote again, I'm not saying the smaller diameter case itself is stronger or weaker. I'm saying that given the same internal PSI with the smaller diameter cases there is less chamber wall tension and bolt thrust, when compared to larger diameter cases. It's a physical/mathmatical truth and, thus theoretically, larger diameter cases need to be built stronger than the smaller diameter cases to withstand the same pressures. The maximum pressure a modern center-fire cartridge case can withstand is largely dependent upon quality of the brass, to some extent case construction, and chamber tightness. Indeed, PO Ackley showed that '06 type cases were as strong as belted magnum cases - it's reported in his famous 2 vol. set. - he found that both case types failed at ~65,000 psi (CUP). Finally, the SAAMI maximum for the 30-06 is 60,000 psi - essentially the same as for the 222 rem mag. SAAMI is strongly influenced by the quality of guns the various calibers are chambered for. | |||
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Within reason the thickiness or diameter of the case head will have no bearing on what pressure causes expanded primer pockets. A 22 Hornet is an exception. Hardness of the brass is the issue. With bench guns the case head is still sticking out of the chamber. But even if the head could be completely enclosed excess pressure will make the brass flow and primer pocket expand. Mike | |||
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I agree with Mike375 - brass quality or hardness is a critical issue in determining pressure at which the pockets loosen up. Indeed, I would submit that .222 cases, .22-250 cases, .257 cases, 25-05 cases, 6mm cases, 30-06 cases, 300 WM cases, 300 RUM cases, and 416 cases would all show signs of stress and begin to fail at about the same pressures - circa 65,000 psi and with blown primers a regular feature at 75,000 psi - that is, if all were being fired in equal quality chambers and all cases were made of equal quality brass. | |||
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So, casehead design has nothing to do with it? Why don't ammo manufacturers load everything to the same pressure level. I'm sure people would appreciate the extra performance. Hell, I'll just put a stronger recoil spring in my 9mm and load it to 65K! While I'm at it, I'll massage my 22 Hornet and enjoy the .22-250-like performance. Just imagine a .44 Mag at 65K! Who needs a .454 Casull? | |||
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The quantity of factory loaded cartridges spec'ed and loaded to about 65kPSI clearly shows that this is just not true. Most reliable data indicates that primers loosen then fail (assuming cases for cartridges normally loaded to 65k) at 75-90 kPSI depending on the brass hardness. This is the reason that the oft given advice is: When you see 'traditional' pressure signs, you are already WAY over and need to back WAY down. For example, a max load in my 300WSM is right up there, and I use it all the time (65 grains 4350 with 180 grain Nosler BT's, look it up yourself...Nosler #5 or Hodgdon's web site) and have only lost one case...a neck split at 7 loadings. This is through up to 10 loadings on 4 differnet lots of brass. Nary a one has a loose primer...even the split neck one. It gives me 2955 fps average and long case life...what's more to ask for in an extra grain or two of powder? Believe nothing, no matter where you read it, or who said it, unless it agrees with your own reason and your own common sense. | |||
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If you had a block of brass 1/2" thick or half a mile thick and hit it with a hammer and nail, the dent would be the same in either case, assuming the brass was equal hardness. Of course if the brass was only 1/16" thick that would be different and would represent the 22 hornet Mike | |||
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CDH, call IMR/Hodgdon and discuss these issues with their ballistic engineers. They're quite friendly. I did and already posted it on this thread, but I'll repost it here. I'd like to know what they tell someone else.
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They`d love to, and they do with new cartridges. The new short mags are a good example. Remember the limiting factor IS the brass, but. The loads in factory ammo are built to the pressure levels of the brass in the weakest firearm it has been chambered in. The 270 Win for example was first introduced in the then new M70. The rifle was capable of holding the heaviest pressures a brass case could safely withstand (~65000 psi) so they desiged the cartridge with these pressures and resulting velocity. Jump ahead 30 years and Remington introduces the 280 in there M74 series semi-auto and pump rifles. The 222 Remington was also chambered in this line of rifles to start if I`m not mistaken. The actions couldn`t hold the pressures the bolt action could and the cartridge recieved a lower SAAMI pressure rateing. Same case, different rifle, different pressure rateing. The same holds with the 22 hornet, 45-70, 32 SPCL, ect, pressure is held to the level the weakest rifles can tolerate and brass in also often built to these standards. This accounts for paper thin 22 Hornet cases and heavy weight 300 ultra mag brass. You won`t find a Winchester M94 chambered in 270 WSM. The case is no more then a gasket and has to work with the vessel it`s sealing to keep either from failure. ------------------------------------ The trouble with the Internet is that it's replacing masturbation as a leisure activity. ~Patrick Murray "Why shouldn`t truth be stranger then fiction? Fiction after all has to make sense." (Samual Clemens) "Saepe errans, numquam dubitans --Frequently in error, never in doubt". | |||
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I'm essentially in agreement with Ol'Joe. Lapua claims they make their brass cases to withstand ~68,000 psi - but not more. Call'em if you don't believe it. | |||
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So your position is that a 222 Remington, if chambered in a Remington 700 bolt-action rifle, can be safely loaded to the same pressure level as a 300 SAUM because the action can withstand the stress? Because if that is the case then what's stopping me from loading 45 ACP to 65K as long as I shoot it from a strong gun like a T/C Encore? | |||
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No, the 222 case is constructed for lower pressures. Remember the semi-auto / pump Remingtons? The same with the 45 ACP the limiting factor is the case. The round was developed to be fired from a pistol at 21K psi. The case and chamber have to work together to hold the pressure and if either isn`t built for the job it isn`t safe. I DO FEEL a 280 Remington or other `06 case based cartridge (35 Whelen, ect) can be fire at the same pressures as the highest pressure round the factory loads in that type case (270 Win)and in a firearm the factory chambers in a cartridge of those pressures. (a rifle factory chambered in 270) The T/C action, I hate to tell you, also isn`t a bolt action. The single shot actions have a tendency to flex when fired and allow cases to stretch. The newer Encore that you mentioned, I believe was developed because of this and is better at resisting it. The Ruger #1 also is a better choice for heavy pressure loads. Just remember there is no gas relief if a case head goes while shooting either. ------------------------------------ The trouble with the Internet is that it's replacing masturbation as a leisure activity. ~Patrick Murray "Why shouldn`t truth be stranger then fiction? Fiction after all has to make sense." (Samual Clemens) "Saepe errans, numquam dubitans --Frequently in error, never in doubt". | |||
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I know. Case construction is a factor. A 222 Remington case is weaker than a 222 Remington Magnum. Similarly, a 30-06 case is weaker than a 300 Mag case. A 30-06 was not designed to operate at 65K PSI. Taking a 30-06 case to that level is unsafe. You cannot generalize and say that all '06 case heads are the same. Just as you cannot say that all 222 case heads are the same. | |||
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Trying to understand what you are saying... the 270 is rated for 65 KPSI. 270 and 30-06 cases are the same, except for neck diameter. I've always been told that the reason the '06 is loaded to lower pressure is that there are older, weaker actions out there, which the 270 never had. Help me out here??? Prove all things; hold fast to that which is good. | |||
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Why don't we section some cases and see? I have some 270's, but no 30-06's. I'll section one right now and measure it. | |||
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Case wall thickness .300" from the boltface is .042" Bolt face to inside of case is .200" Flash-hole depth .065" Case wall thickness at the flash hole .070" | |||
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Case wall profile forms a parabolic curve that may be varied for each application. That is not possible to measure. Also, case head diameter is .470" What is the diameter of a FC 30-06? | |||
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The (origional) Winchester M-95 lever action was chambered for the 30-03 and later the 30-06. There are still some out there, (my Uncle still hunts with one) and more than a few of them have come apart also. Same is true of SAMMI spec on the 8mm Mauser, pressure is held down incase someone fires it (with the .323 bullet) in a older (.318) barrel | |||
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Ralph, I'm pretty sure that 270 and '06 cases are identical, except for neck diameter. This is once I'm willing to go out on a limb, without actually measuring them. I think Tailgunner is right on with his statement about the M95, and SAAMI specs. SAAMI has to specify ammo that will fit and work in all the guns out there. Factory ammo has to be safe for the M95. If you have a strong, modern action, I think you are actually allowed just a little more pressure in the '06. Personally, I don't take advantage of it. Why bother? It's harder on the gun, harder on you, and it doesn't make the elk any more dead, nor does it really increase your range that much. Prove all things; hold fast to that which is good. | |||
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Denton is correct the internal construction and brass quality of the 30-06 is identical to the 270. The 30-06 case gave rise to a number of wildcats - 270, 280, 25-06, etc. They were all derived from the same basic parent case. Call Lapua - they'll tell you they build all their centerfire cases to withstand the same internal PSI - they guarantee at least 68,000 psi. | |||
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I'm going to go out on one more limb here, and put out an opinion that I can't substantiate. When you fire a cartridge in a modern rifle, the circumference of the barrel stretches about .0005", more or less, and then snaps back to nominal. That's known, and measured. Similarly, the chamber stretches lengthwise, and snaps back. I can't say how much the actual stretch is. That's where the opinion part comes in. Inside the chamber, the brass has to stretch lengthwise along with the steel. When the pressure is relieved, of course, the steel snaps back, and the brass is compressed. I suspect that this repeated stretching and compression is a major actor in getting case-head separation. So, yes, the brass fails first, but the strength of the action and the pressure of the load help determine when that happens. I think that when Lapua says their cases will withstand 68 KPSI (and I have great respect for Lapua), I think they are saying that the internal pressure in the flash hole and primer pocket will not excessively stretch the diameter of the case head at that pressure. That's a different issue than the one mentioned above. BTW, a .001" (very large!!) case head expansion will result in about a .002-.0025" primer pocket diameter expansion. It seems like they ought to be the same, but they are not. Prove all things; hold fast to that which is good. | |||
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Denton, likewise that is how I interpreted Lapua's comments - pockets will take at least 68,000 psi without failure. Like you, I believe more is need to create case head separation - much more. | |||
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AIU, I think we're starting to be in violent agreement on this topic. But part of my point was that it may take 80,000 PSI to create a head-case separation in a single shot, but that lower pressure will create one after several shots. The brass fails, but the steel isn't innocent. Prove all things; hold fast to that which is good. | |||
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Regarding safety problems or concerns, below is the official policy of IMR/Hodgdon Powder Company. Many of the topics we have discussed here, their technicians are happy to discuss with you - they have been with me! I encourage you to call and get their opinions on these issues. "If you have a safety problem or concern - DO NOT EMAIL - CALL US [ie., IMR/Hodgdon] DIRECTLY - 913-362-9455 If you require an immediate reply - CALL US -913-362-9455 Send email to help@hodgdon.com with questions or comments. Hodgdon Powder Co., Inc. Phone 913-362-9455 Fax 913-362-1307" Have a happy and safe weekend and good shooting! Regards, AIU | |||
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Denton, as you know, I've loaded quite hot with multiple reloadings of one case - at least several times with pressures ranging from 65,000 to 75,000 psi. I've never experienced a case head separation. I've blown some primers, sometimes on cases that have already been loaded hot several times - again no case head separation. Admittedly, I throw away the cases as soon as the primer pockets get loose. This may be from having first-rate guns with tight chambers, trued actions, after-market Hart barrels, etc. But, my sense is that case-head separation takes some REALLY SERIOUS PRESSURE - at least 80,000 psi and above. Modern brass seems to be of quite high quality. I don't like getting this hot and try to stay circa 65,000 psi for my long-range big game loads. Moreover, I only shoot that hot a few times a year. | |||
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So if that's the case, then I will proceed with my 222 short meck AR-15 project. If I blow up my AR-15 I'm holding AI personally responsible. Well not really, but if Lapua says their 222 case will hold 68KPSI, then I shouldn't have any problems. | |||
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Ralph, I think that loading to 70 KPSI is asking for trouble. But, AIU and I have read each other's posts, and we disagree, and that's fine. I'm perfectly OK with that. I think he understands what I have said, and that's all I can ask. The one thing I cannot resolve is the issue of how case head strength can be independent of geometry. I think that it simply resolves down to considering a brass tube, with the same OD as the case head, and the ID of the primer pocket, or flash hole. If a brass tube with those same dimensions can hold 68 KPSI, and not go into yield, then all is well (give or take a case head separation). But I do not understand how a case head that is 223 size can have the same yield strength as a case head that is 30-06 size. It seems to me that the fatter tube will hold more pressure, unless the differences in ID account for this. It is NOT the pressure of the gasses pushing back on the head that causes head expansion. It is the pressure of the gasses in the flash hole and primer pocket, pressing outward that causes it. So I can't "see" how case head expansion is independent of geometry. SAAMI rates the 222 at 50 K, and the 223 at 55 K. Until I get better understanding, I think that is because the OD is smaller than, say, a 30-06. Prove all things; hold fast to that which is good. | |||
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I was looking at it from a simpler standpoint. I became interested when looking into a way to shoot 80 grain bullets ftom the magazine of an AR-15. I decided that a 222 with a 223-length neck would allow this with velocities close enough, with easily obtainable brass, and cheap chambering reamers (223 reamer run short). I then looked at max pressures for the 222 and the 223 and realised the 222 to have a lesser rating. Why? I sectioned a W-W 222 and a 223, finding the 223 to have a much stronger casehead design. Now comes along AI, claiming that every Lapua case can withstand 68KPSI. If this is true, then I'm back in business. I don't plan on approaching 70KPSI, but I wanted the same pressure level capability as the original 223. I have a different way of gauging pressure that I have been using for many years and it has proven reliable. I'll be using it to work-up the load. I just needed to be confident in the strength of the brass. | |||
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My current opinion is that, all other factors equal, NO smaller diameter case can withstand as much pressure as a larger diameter case. At the moment, I do not see how all of Lapua's brass can really stand 68 KPSI. Just because I don't understand it, doesn't mean it isn't so. But, at the moment, I'm very skeptical. I'm concerned about what you're contemplating. Why don't you drop a note to Ken Howell? He certainly knows more about it than I do. His health hasn't been the greatest lately, but he seems like the kind of guy that would answer that kind of question for you. He's easy to find. His ad is often at the top of the page at huntchat.com. Prove all things; hold fast to that which is good. | |||
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Well, Here is how I plan to go about it: Since I have every flavor of VV powder, I'll start with a caseful of N560 and work my way down  | |||
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Denton, I`ve always been under the impression the chamber helped support the case head and this was a factor in how the brass reacts to pressure. If you look at a Glock pistol, it doesn`t fully support the case and they are known for the bulge in the fired case. The brass may well handle the pressures Lapua states as they also are giveing the figure as a minimum pressure for their line and other cases could handle more, they just don`t advertize it. ------------------------------------ The trouble with the Internet is that it's replacing masturbation as a leisure activity. ~Patrick Murray "Why shouldn`t truth be stranger then fiction? Fiction after all has to make sense." (Samual Clemens) "Saepe errans, numquam dubitans --Frequently in error, never in doubt". | |||
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Maybe I haven't made myself clear. No case - not even the great 300 RUM - will withstand by itself 68,000 psi. The brass case must be surrounded (supported) by the bolt and the chamber! But, when supported, Lapua says their cases will withstand internal chamber pressures of 68,000 psi without failure. I work with bolt-action rifles that have been worked over (improved) by a first-rate (nationally recognized) benchrest rifle gunsmith. I would never experiment at these maximum pressure levels with a semiauthomatic, automatic, or lever-action gun - especially not an AR-15. Automatic weapons have been designed for specific types of ammo - I wouldn't deviate from the ammunition they were designed to shoot. Why would you want to? | |||
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Why would you deviate from ammunition your Remington 700 was designed to shoot? Besides, an AR-15 is extremely strong, and can easily withstand tens of thousands of maximum pressure loads. You would soil yourself if you knew the pressure level of the AMU 80gr load. It toasts their barrel in under 3000 shots (mixed). I'm surprised that an adventurer like yourself holds a lever-action above a gas actuated bolt-action (AR)! | |||
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I think that having the brass fully supported by chamber and bolt is important for one failure mode, case-head separation. I think it is not for another failure mode, case head and primer pocket expansion. The case head has a thou or two clearance all around. Unless the case is absolutely snug against the chamber (stuck), the chamber will not restrain it from growing. Supporting the case with the bolt will make no difference in that failure. It is not the pressure of the gas pushing back on the bolt that makes the case head grow. It is the pressure of the gas in the flash hole and primer pocket, pushing outward. Prove all things; hold fast to that which is good. | |||
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No doubt that primer pockets and case heads will expand (grow) inside the bolt-action chamber when exposed to pressure - we agree on that. They will expand at SAAMI max pressures too, just faster at SAAMI plus pressures. Again, I believe in limiting maximum loads to strong, well-made, bolt-action rifles with well-vented actions. | |||
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In regards, to using a chronograph to estimate PSI, I think this thread is relevant and worth viewing again, especially in it's discussion as to what's excessive PSI. | |||
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Hey AIU, Just looked back through that fine thread. I agree I got a few  from it. | |||
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Hot Core, whatever happened to Denton? Regard, AIU | |||
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 Denton Bramwell has sought forums without the evil engineer 'hot core' that scrutinizes and denigrates every logical and mathematical error. | |||
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"The World's Most Stupid Reloading Suggestion" that he made, along with the Lies he told, finally moved him to a new forum with more people for him to fool about Haphazard Strain Gauge Systems.
  I seem to remember having a bit of help from another right knowledgeable Engineer who is known to Ka-Boom firearms on purpose.  | |||
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