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What is the term for the secondary dotonation effect of slow powders ie(4831) when loaded w/ not near case capacity called and expand on this for me thanx, Doc Stone   | ||
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As far as I know it's called 'detonation'.This is in contrast with the normal 'combustion' of the powders.It has been a problem known for some time though it took a while to be duplicated in the laboratory.It occurs when very slow powders,in rifle or handgun, are used with reduced loads. By reduced meaning more than 5 or 10% below max.Important to be aware of but easy to avoid, if you want reduced loads just use a faster powder. | |||
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It is called "urban legend". This has never been documented in the real world. | |||
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It is NOT urban legend! There have been at least a couple of articles in Handloader magazine wherein the phenomenon was duplicated AT WILL, and other publications and authors have also reported it. My own wife had a Browning Safari-grade Mauser blow up in her hands from this effect. One of the more persuasive theories today, with the pressure-measuring advances that we have made recently, is that the burn progression of the charge is not always a smooth curve as we have been led to understand, but rather (at least in some examples) is a series of pressure peaks and lows which often come perilously close to being actual hangfires, and if the bullet stops during one of the pressure "valleys", the next pressure rise can escalate enormously as it meets the resistance of the stopped bullet. In the case of my wife's Browning (7mm Remington Magnum), the bullet was found just three or four inches ahead of the chamber and practically the entire charge exited the rear of the chamber. It melted the case head, giving extensive brass-plating throughout the action, blew the extractor and bolt stop off the rifle, blew the mag walls through the sides of the stock, blew the floorplate, follower, and follower spring out of the rifle, and even badly distorted the steel bolt shroud at the REAR of the action. The bolt lugs were set back into the receiver ring, and the third lug was bearing hard in its recess, where it normally doesn't touch anything. My wife suffered some rather dangerous injuries, as well, and bits of brass and steel were working their way out of her face for many years afterward. The shot that "blew" was fired only a few seconds after a previous shot which struck her target, so we know the bore was clear. Over 100 rounds of the identical load had been fired in practice before the hunting trip, without any problems whatever. | |||
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IIRC, the man from Hodgdon said in Reloader magazine that he could not duplicate in the lab with lots of trying, but later got it to happen with a .243, very slow powder [IMR4895 is too fast], half filled case, and a throat so rough that he bullet could really get stuck in it. The rough throat part is what was missing in the lab. | |||
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Great stuff guys just hang a name on it so I can go to another board AND BE THE EXPERT thanx much Doc StonePS- Steve I don't think you got any friends.. only kidding kinda sortof. | |||
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Steve's right.......And Bruce Hodgdon, who probably knew more about powder than any man alive, was never able to duplicate the effect....Ackley never saw it......Jack O'Connor supposedly saw a 270 Mauser blown with H4831, but later thought it was mistakenly loaded with Hercules 2400. Bob Hutton dismissed it, after trying to produce the phenomena...When reduced charges in large capacity cases are fired, the rifle don't kick much, and the bullet comes out slow.......Grant. | |||
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| <eldeguello> |
WOW!! What an experience! I hope your wife recovered from this incident!! BTW, do you recall what the load was that did this? | ||
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Quote: Damn! Am I ever going to lose sleep over that tonight. But, then again, I am not here to win an election, be voted most congenial, and to make friends or be nominated as "Mr. Popular". I am here to share my knowledge and experience with those who are receptive.  | |||
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This happened quite a while back, but I remember the load. The bullet was a 175-grain Nosler Partition ahead of 65 grains of H4831. Every single charge was weighed and loaded in brass once-fired in that rifle, and as mentioned we had fired over 100 rounds of this load before the hunt. My wife was very fortunate. Her glasses protected her eyes, and were pitted and scarred to uselessness. Two fingers were broken on her left hand when the mag blew through the sides of the stock, and her left wrist badly sprained along with a deep cut on the wrist which came perilously close to the artery. There were a lot of other, more minor, cuts in various places. (She then whipped out a Ruger .44 and killed the bull moose which was the object of the exercise! One-handed, from 65 yards yet, two rounds in the neck....gutsy) For the doubters out there, how often do we hear of such blow-ups? Compared to the number of rounds fired in our various activities, the number is statistically miniscule, almost to the vanishing point. Compared to the probably MILLIONS of rounds fired in daily shooting activity, how many test rounds do you think the labs tested??? Again, I'd say the ratio is tiny to the vanishing point. The fact that the labs couldn't duplicate it in a LIMITED number of rounds does NOT mean there's nothing happening in the field! This subject comes up every so often, so I reckon I'll try to find one of the Handloader articles again, and quote y'all some quotes. It is still extremely good advice to not load reduced amounts of slow-burning powder! | |||
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A name>> a name >>my kingdom for a handle(name) thanx Doc Stone Steve I appreciate you bank fo knowledge which you so readily share... | |||
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H-4831 From 53.7 grains to 70.0 grains CCI-200 Primer Your 65 grain load was not the cause. I would look for another reason. The two most common would be the wrong bullet or the wrong case. A third could be some sort of barrel obstruction prior to firing. | |||
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Steve, pard; First, let me assure you that I am NOT belittling you in any way, nor am I unappreciative of all you have done for reloaders with your website. THANKS!!!! Now; 1. All the loads were in once-fired cases, fired in the rifle that came apart. No wrong case, in this case (pun). 2. All the loaded rounds were test-cycled from the magazine before the hunt, and functioned perfectly (e.g.: there wasn't a .30-caliber bullet seated by mistake). Also, 175 grains is normally the heaviest bullet commonly available in 7mm, so I didn't substitute a too-heavy bullet and drive the pressures up that way. 3. The rifle had been fired mere seconds before the round that took it apart, and that bullet struck the target (moose). Ergo, no bore obstruction. And remember, the bullet was found IN THE BORE, barely three inches ahead of the chamber. It's my strong belief that a hangfire occurred,leaving the bullet in the bore ahead of the chamber, and also leaving greatly-increased volume behind the bullet. THIS WOULD CREATE EXACTLY THE SAME EFFECT AS A MUCH-REDUCED LOAD. The hangfire theory is also supported by the fact that there was a major shoulder collapse on the case, running a full third of the case-length. Shoulder collapses are symptomatic of very low pressures, insufficient to seal the case wall to the chamber wall, and thus allowing gas to flow back and dent the case. When the extreme-pressure event occurred on re-ignition, I surmise that the pressure both inside the collapsed area and outside the case wall were equal, which preserved the dent while still blowing the rifle up. It was a nasty occurrence, for sure. I'm looking for those Handloader articles, but it may take a while. | |||
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S.E.E. Secandary Explosive Effect is that the name your looking for? This rifle had a tight 9 shot group going, when the 10th round was fired this occured. The rifle is hanging in my gunsmiths shop, and he is VERY familier with the incident (and effect) as it cost him a couple of fingers.  | |||
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that'll work now forget that kingdom stuff thanx much Doc | |||
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Bren........not belittling you in any way, But....what you are describing exactly, is firing a high-powered magnum rifle, (7mm Remington Magnum), with a full load, behind a bore obstruction.......That's not detonation, that's bad shooting practice........And no matter what caused the accident; whether it be a faulty primer, a sluggish firing pin fall,( Was the hunt in extremely cold weather?)or a dangerous hangfire, the resulting disintegration of the rifle, wasn't the result of any mysterious secondary explosive effect.......And contrary to your observation, a much reduced load, say, 50%, would probably have resulted in 50% less damage to the rifle, and the shooter. "Extreme pressure occurred on re-ignition"....No, normal full-powered, magnum, rifle pressures occurred....... They can be very destructive when not contained properly. Luckily the bolt was not being opened when the hangfire happened. Sounds like your wife is very brave, and very lucky. Grant. | |||
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Gentlemen: I have now described EXACTLY what happened, TWICE! THERE WAS NO BORE OBSTRUCTION. THE BULLET STOPPED IN THE BARREL AHEAD OF THE CHAMBER. Is that clear enough? The FIRST bullet exited the barrel and struck the moose. The SECOND bullet stopped in the barrel ahead of the chamber throat. There was NO bore obstruction for the second shot. "Bad shooting practice"??? Are you suggesting that we would shoot with an obstructed bore on purpose? I've been handloading for forty years, and have never before heard such an absurd statement. As for the pressures involved, you're not talking to a neophyte here. I was there, I disassembled the rifle after the event, and I know what I found. It was NOT normal pressure for a magnum load. The pressure was "not controlled properly"? With a magnum-caliber rifle PROPERLY locked for firing, as it was in this case, when was the last time your "normal pressure" MELTED the case and destroyed the rifle? I am not given to wild theorizing, but I do have a lot of rifle and handloading experience and also an ability to see and interpret what is in front of me. | |||
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Bren Mk1 I personally don't buy the Secondary Explosion theory (in terms of generaating excess pressure and for a simple reason. It is my understanding that when ignition is correct then all the powder granules ignite at once and the "burn" is controlled by each granule as opposed to the "burn" being controlled by a gradual ignition of the powder granules. Thus "detonation" in the way it usually meant, that is all the powder ignites at once, should happen with correct ignition. When it does not happen then you have a hangfire. Now whether some type of "shock wave" might occur I have no idea but this has been raised over the years. However, such a shock wave would not result in melted case heads. I believe I know the reason that is the foundation of the Seconday Explosion idea and it can be demostrated quite easily and with ball powders being the main offenders. When ball powders are used that are too quick for the calibre (eg Win 760 and 7mm Rem)an extremely small hangfire can occur that is too small for the shooter to notice. However, the very small hangfire does reduce the pressure that should have existed. This in turn allows the shooter to increase the load and he reaches a point where the amount of powder is well above what should repesent a maximum load. Then as the powder takes up more of the case volume he gets correct ignition and then the full pressure that should occur with such a load. A similar situation can and does happen when using quicker powders like 4227, 4198 in very big cases like the 378 Wby. In this case and also the 460 Wby the very large freebore also adds to the hangfire problem and allows the shooter to exceed what the maximum load would be when using a powder like 4227 and so on. As a side note, about 20 years ago my father worked up a load using Win 760 with 180 grain bullets in a 308 Norma Magnum. The loads were worked up firing down a hole. I told him that in my opinion the amount of 760 was too high and pressure was showing as mild because of the combination of using 760 and shooting with the rifle point down. The next day he took the rifle out with a mate of his and when he got home he said to me "guess what happened". The first shot from the rifle was a significant ovedrload with blown primer. In short, he was getting an extremely small hangfire when testing the 760 by firing down the hole. I am not in any way doubting that your rifle blew up but I think the reasons are different to what you are thinking. Mike | |||
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Quote: I'm receptive! I'm open to any and all info, But I saw with my own eyes, an article on the web, (now I've got something to do tomorrow) which describes the condition, symptom and cause of the secondary high pressure spike ( I think that's what your talking about) It MAY have been the Ohler site. I do remember it was one of the manufacturers of the strain gage based pressure measurment tools. ("something" lab?) The documented VERY clearly a secondary spike and had a reasonable explanation even. I just have to say, it's impossible to prove something DOES NOT exist. Show me on google. | |||
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Bren, I don't think OM70 is saying there was a bore obstruction before the fact, he's saying the bullet became the obstruction. What you describe sounds like a hangfire that had enough initial oomph to create the obstruction then came back to finish the job. You're collapsed shoulder on the case supports this. Your evidence does not support the detonation theory. FWIW, Ross Seyfried did an article awhile back in either Rifle or Handloader wherein somebody fired a 7 Mag in a .270 Roy. The bullet made it about 4-6" down bore, the rest looked about exactly as you describe it, including the brass plating effect from the missing case head, this with factory ammo. | |||
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If only Elmer Keith were here, he'd have the answer for us on the spot... From my recollection reading of this situation it has to do with too small a charge of slow burning powder in a large case. You get a detonation rather than the proper "burning" and therefore pressure BUILDING by the powder. I think it also has to do with the position of the powder charge as it sits in the case at the time of ignition. Too much air space basically. I'm going to my library to dig for this in Elmer's books, I'm fairly certain I've it discussed by him. | |||
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If ANYONE reproduced it anyplace, it would be in every publication known to man. So figure its like crop circles.. | |||
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There are a lot of theories of how it might occur. I've seen the ones about hangfires partially moving the bullet into the rifling, then the powder rapidly flaring up with the bullet "stuck," about loose powder ramming into the shoulder of the case, breaking the powder grains and producing too-rapid combustion, about reflected pressure waves reinforcing one another and producing localized peaks way above the average pressure, maybe another one or two I can't recall. Here's mine: Powder grains do ignite more or less at once when there's enough flame from the primer to fill the case, and the burning rate of the exposed surface of the individual powder grains controls the bulk burning rate. Each grain burns on a very thin layer, progressively taking layers off the surface. The rate of burning for the surface area is determined by the composition of the powder (the surface deterrent coatings and deeper layers with some deterrent in them burn more solwy than the core of the grains with no deterrent), the temperature and density (which is a function of pressure) of the gas surrounding the grain, wich along with radiant energy determine how fast each thin surface layer as it's exposed can be heated to ignition temperature), and as we all learn from experience, the initial temperature of the powder influences it. Start with warmer powder, and it burns faster producing higher pressures. I think that it's possible for a hangfire to produce a smouldering flame that heats the powder grains deeply, so that when it flares up the heated powder will burn much faster than normal. Most explosives, perhaps all, exhibit a behavior under some conditions where deflagration (the orderly burning in successive layers) can spontaneously transform into detonation (with the explosive decomposition spreading through the material with a supersonic shock wave.) That's usually been described in fairly large bulk charges and would be improbable with granulated smokeless powder in the size charges used in rifle cartridges, but preheating the grains might be one way it could occur. Someone on here several months back insisted this effect had never been reported with cast or lead bullets. Others have said that it can't happen in a straight case. Interesting to see that one blown up with 15 grains of 3031 under a 500 grain cast bullet in a .45-70. Personally I doubt the stories of this happening with the fast burning flake pistol powders in small charges. I think what's happening there is more likely to be inadvertent multiple charges. | |||
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OK fellas, here's Elmer's take on it... I'm quoting him from his February 1968 Gun Notes. This is a bit long, but it's classic reading from a man who had an uncanny genius for this stuff... "While it is rare, there have been all too many rifles blown up with reduced or light charges of slow-burning powders. Many theories have been advanced at to the cause. Iver Henriksen has a model 70 Winchester rifle that was completely shattered with a reload of 4350 powder in caliber .264 Win Mag. It would seem almost impossible to get much of an overload of this powder into the case. Many investigatred the case, as the shooter lost his right eye and cheekbone from the bolt coming back, but they arrived at no positive conclusion. The receiver and bridge were all blown to bits and the stock to slivers. In fact, it was the most completely wrecked rifle I have ever seen, and I had several blow up at Ogden arsenal and some cut right in two pieces at the receiver with standard factory arsenal "war" loadings. "My own theory on this blown-up .264 with 4350 powder was that the charges were thrown from a powder measure without either weighing or final visual inspection, and the powder somehow clogged in the tube so that a lighter-than-normal charge was thrown. When fired, the primer flash ignited too much of the charge at once, causing a detonation. These slow-burning powders, when packed tight in the case, ignite the rear end of the charge, and it burns forward, pushing the rest of the powder up against the bullet and forcing it down the bore until the charge is consumed. Thus we have slower ignition of the whole charge, and it is extended up the bore of the rifle, but if the flash of the primer goes through the whole of a very loosely packed charge and fired it all at once, that could be the cause of these blowups with slow powders and light loads. "O'Neil, Hopkins and I early learned that compressed or tight charges always gave more uniform velocities and better accuracy than loose charges of powder. We also learned that for any reduced or light load, a fast powder should be used and never a slow-burning powder. "...Airspace loadings of modern smokeless powders allow the charge to be thrown from one end of the case to the other as the muzzle of the rifle is lowered or elevated in firing, causing some variation in ignition and also combustion of the powders. I, for one, do not like airspace loadings in modern high-velocity cartridges. Smallbore rifles with large cases are the most dangerous to reload and largebore cases or straight cases seem never to develop the high pressures of bottleneck cases..." | |||
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| <eldeguello> |
Mike375, NO excessive pressures, in the ordinary meaning of that term, are generated when this happens. What takes place is that instead of continuing to burn at the designed rate, the propellant transitions from a burn to a hyper-velocity detonation wave, which no mechanical means, such as a rifle barrel and action, can contain. In the early days of nitrocellulose, when experimenters were attempting to harness its energy to propel bullets, it happened all the time before chemists discovered a way to alter the physical structure of the nitrocellulose to cause it to burn rather than explode. If you read Bren's description of the condition of his wife's rifle after the explosion, you would realize that what happened was NOT due merely to a pressure excursion, but to an HE detonation. If the cartridge had been loaded with TNT, the results would have been very comparable. | ||
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| <eldeguello> |
Quote: Right! The Krauts knew about and were using noncorrosive primers in their sporting arms ammo for at least ten years before it was "discovered" in the U.S. ...  | ||
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If you ever get to have a chance for a private conversation with a powder company ballistician, ask him about the industry experiences with "pressure excursions" in the 7mm Rem mag and the 243Win. For obvious reasons, the labs don't always share their experiences with the public. Personally, I find the "bullet becomes an obstruction" scenario entirely plausible, but no matter the cause, there are a few chamberings out there that show tendencies toward pressure spikes, more than others. JMO, Dutch. | |||
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There is one other aspect of the 65 gr H4831 under 175 NP that needs addressing. Hornady lists a Max load of 57.9 gr IMR4831 for that bullet weight(not bullet), while Nosler lists 60.0 IMR4831 as Max for the 175 NP. Hornady 5th and Nosler #4. Hodgdon on the other hand says for that bullet weight, 61.0 grains of H4831 is Max. Bren, it would appear that at the very least your wife's event was not caused by a reduced load. | |||
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Quote: In the February 2001 "Handloader" magazine, John Haviland's article on reduced loads quotes Ron Rieber of Hodgdon. | |||
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Quote: This is how I had understood it also. | |||
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Quote: Hey Doc,How `bout them Cardinals< !--color--> ?  Interesting that folks still disagree on this subject. I've heard it refered to as: 1. Secondary Explosion Effect 2. Pressure Excursion 3. Detonation It is apparently understood by a good many folks. There are excellent Chapters on it in both Volumes of PO Ackley's "Handbook For Shooters & Reloaders". The subject was discussed a good bit in my youth through the various Gun Rags of that era and the NRA American Rifleman. For those of you that know I'm not a fan at all of the "Home Strain Gauge Systems", there was an interesting set of flicks provided by one of the HSGS users in the following thread which actually captures what is happening inside the rifle when this occurs. http://www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Board=UBB6&Number=717045&page=15&view=collapsed&sb=5&o=93&fpart=2 Interesting to me that there was a lot of discussion about "What?" was actually happening by a good many folks who have the HSGSs, but they had no clue at all. As you can see from reading the thread the only guy (Bert that makes a HSGS for sale) that had any idea at all what the correct answer was. That is one of the HUGE problems with the HSGS, many times a person who knows little to nothing about Internal Ballistics buys one and believes he is now an immediate Expert Ballistician. And then has no concept of what the equipment is indicating. Even Mr. Sisk was able to blow the end off his rifle using the HSGS which indicated there were serious Pressure Problems. Had the Peak of the Secondary Explosion Effect occurred a bit closer to the time of ignition, then he would have seen the rifle come apart at the Chamber. So folks, you can argue to your hearts desire, but the flicks in that thread show a Secondary Explosion Effect occurring. Fortunately at a level where it was contained. When a Manual written by a company with access to millions of dollars worth of Test Equipment says, "Do not load this Powder below the minimum!", there is a good reason for it. | |||
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| <eldeguello> |
Quote:And, 4: "Deflagragtion to detonation transition" (DDT) This implies that the powder starts off by burning, but during the process, an actual detonation occurs. If true, it would certainly explain the catastrophic failures of some pretty strong rifles..... | ||
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Quote:Quote: HotCore, I followed the thread you refered to, both here and at 24hr campfire while it was running. The problem Mr Sisk and Denton reported was with "normal" charges of slow powder under a light for caliber bullet, not a reduced load. Mr Sisk blew the brake on his rifle by questioning the test equipments report of a spike and adding powder. This is a bit different then a lower then recommended charge causing a mishap, although the resulting pressure wave may well be similar. Both reported to be able to achive similar results (secondary pressure excursions) at will useing selected componts but not at reduced charge levels. IE: Light for cal bullets and listed recommended charges of very slow powders. I agree with you, one should stay with listed charges and not excede or go below them. The writers of the manuals have a reason for the min / max they list and I suspect they know more about secondary spikes then they let out to the public. I think DigitalDan has it though, the charge might be too high. I cheacked the following manuals and found the highest charge recommended for a 175gr bullet in the 7 Rem Mag to be 64.5 in the Sierra # 3 & 4 the new # 5 lists 63.3 as max. The others maxed out at < 61 grs. Speer # 13 Nosler # 5 Lyman #`s 47 & 48 Hodgdon #`s 26 & 27 | |||
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Gents; Being a packrat I rarely toss out old books and similar artifacts. That's a good thing for me, today. All you second-guessers on the 7mm Magnum load, please pay attention. 1. This episode occurred in 1974, just a few miles south of Great Slave Lake in the Northwest Territories. 2. The powder was military-surplus 4831 in a 20-pound drum. Lot-to-lot variation can drastically affect loading parameters, and even today those of us using surplus powders must be very cautious to take this into account. My drum of 4831 was appparently quite close in burning rate to the stuff used by most of the handbook producers, though. I certainly never got close to that Lyman load! 3. The identical 65.0/175 load had been used for HUNDREDS of rounds in that rifle, with at least three different manufacturers' bullets of that weight, with excellent brass life and accuracy, and velocity within the expected range (yes, I was chronographing my loads in that time and place). 4.The data of THAT TIME supports the load. -Hornady Handbook, Vol II, copyright 1973, says 64.9 grains max with 175-grain bullet. -Speer #7, bought in 1968 by my flyleaf note, says 64.0 with 175 grain bullet. -Speer #8, copyright '70, says 65.0 grains with 175 bullet -and Lyman #43 (1964) says SEVENTY GRAINS of 4831 with a 175 grain bullet. I remind you again that we were dealing with SURPLUS powder, and even Hodgdon had not yet commenced selling new-production 4831 at that time. I suspect this is why Lyman came in with a load that high, that is, having a different lot of powder. THESE were my information sources for loading 7mm Remington Magnum ammunition in 1974, and I submit that I was NOT foolishly overloading my wife's rifle. Just wanted to set the record straight.... | |||
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