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Awesome string denton and Idaho. Copy, combine, and dump into a Word document and you have your next article. JCN | |||
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Mike, I wasn't referring to you... I might not have agreed with everything you said on that thread, but you made a very valid point. Establish a 'ceiling' and work back from there. It isn't the way I like to do things, but that doesn't make it invalid. | |||
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Peter, One of the main reasons I do it that way, and this ironic given the Australia thread, is to preserve brass and not learn on the 4th shot as the primer loosens that the load is bit warm. This has been a product of loading over the years for the 378 case based Wbys as well as some wildcats that require fireforming. In either case you don't really want to find out that load is too warm after you have fucked a 100 cases  The Oehler 35 is not a complete guide when you muck about with powders that are faster than normal for the calibre.Mike | |||
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Mike, we're definitely on the same page, just that your ceiling is probably higher than mine. I wouldn't mind betting that our approaches are very similar - in my 270, I load 3 rounds each at half grain increments from about 5% below highest book max to maybe 2g over. I look for the 'sweet spot' in terms of accuracy - which is rarely at max. I fire a few of the higher loads until I see a bit of primer cratering, and then make my decision from there. The unfired loads get pulled. I then work on that 'sweet spot' in .1g increments - I get outstanding accuracy that way - velocity doesn't interest me in the slightest. My ceiling is primer cratering, yours is extractor marks - different ceiling. | |||
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John, WOW!!! that's the PERFECT use for a model 700... an extractorless testing platform!!!! jeffe | |||
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Quote: 280 Remington Ackley Improved 35 Brown Whelen http://www.shootingsoftware.com/ftp/dbramwell%20july%2019%2004.pdf | |||
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Quote: Quote: according to which book if both are using identical components and barrel lengths. I notice that neither you nor anyone else has attempted to explain and answer the following. Quote: It appears that a number of people have different theories,speculation and calulations as to whether fast and slow barrels do exist.Unfortunately the only way to actually prove this one way or the other would be for someone to install a number of barrels of equal length,say ten for an example, on a receiver such as the one posted by Lawndart.To really add credibility to the test one should use a mixture of factory barrels,lapped barrels,cut rifled barrels,hammer forged barrels,button rifled barrels,stainless and chromoly barrels.One would then have to work up loads with each barrel using identical components until the chamber pressures are identical with each barrel.If the resulting velocities from each barrel were identical,the theory of fast barrels would be disproven.If some barrels did produce more velocity than others the existance of fast barrels would be proven.Unfortunately the costs,machining required and time will probably prohibit such a test from ever taking place.However until such a test is performed under controlled conditions,there won't be any absolute proof as to whether fast barrels do or do not actually exist and the theories,speculation and calculations will remain just that. | |||
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Quote: That's a heck of a good question. The books don't agree, so which (if any) do I believe? My opinion is that the safest bet is to take the average of a few or several books. Also, everybody knows that SAAMI sets pressure specs. Less well known is the fact that there is also an MV spec for each round, usually with several different bullets. For the '06, and a 180 grain bullet, the SAAMI MV spec, with the chrono 15' downrange, is 2690 fps. Now I'm not sure I have a real good answer to the second question, but I will take a stab at it. The one time that I've actually seen that happen was with my 308 and some AA2520 powder. I made up about 10 cartridges, in pairs, at some increment of charge. For the first couple of charges, MV went up linearly with charge. Next pair, no real increase. Not having my wits fully engaged, I went on to the next pair. Still no change. Then the penny dropped.... As you increase charge, you reach a point where you get no additional MV, but you do continue to build pressure. The pressure curve increases exponentially, and the MV curve starts to be more logarithmic. The place that the two curves part company is known as "the delta". What I was seeing was an unusually sharp transition... linear increase, then a "flat-top". So, if you're into a situation like that, you can get pressure signs before you get the "book" MV. There may be other situations, but none occur to me at the moment. If you read my posts carefully, I say that if you reach "book" MV, you need to stop increasing the load. But I have not said the opposite, that you can safely increase charge to equal book MV. The cases you cite are one good reason. I think that a fair statement is that you should stop at the first sign of excess pressure, whatever that may be. I also think that a graph of MV vs. charge is helpful. It will be quite linear, over a short span of charge values. However, kinetic energy is the value that should be truly linearly proportional to charge, and KE is 1/2 m v^2, so MV isn't linear over a long span. Quote: They manifestly do exist. All the barrels used by SAAMI for testing ammo are fast barrels. Why are they fast barrels? Because they are cut to minimum dimensions, which creates a smaller volume for containing the gas. That creates more pressure for the same amount of powder. There are, as far as I can tell, no "magic" barrels that produce something for nothing, i.e., unusually high MV with no accompanying unusually high pressure. | |||
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denton: Quote:EXACTLY!!!!! This is also my contention.....in using my example of case head expansion "CHE"....thanks for the link Jackfish.... it is not my assertion that it's a reliable tool to determine a "SAFE" load, but rather that it's a good indicator of approaching an "UNSAFE" load. The difference here is dramatic.....one fails on the side of safety.....the other fails on the side of .....wellll...not so safe!!! Any additional velocity I might have achieved by going beyond the early warnings.....even if they are not reliable, is better than the alternative and the loss of 100'/sec is no loss in my book.....not with such cases like .22-250 and bigger. These are purely emotional gains. | |||
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The problem with stopping when you get a PRE/CHE pressure indication is that it can stop your '06 load development as early as 45 KPSI. If you're willing to put up with that possibility, then you're fine. It's not the PRE and CHE can't be made to work. They can. They just have a lot of random noise, and it takes a lot of averaging to get a clean signal. By the time you go to all that trouble, it's more economic to simply go to a strain gage. | |||
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I haven't done ten barrels but if three might do. I've tested three different 300 Win Mags, all with 26" barrels. The first was a factory Winchester. The second was the same gun with a Douglas barrel installed. The third was a custom gun that I did for a customer (don't recall who made the barrel). From the "fastest" to the "slowest" there was a 7% difference in the powder charge that would give equal velocities. When the powder charge was ignored and they were loaded to the same pressure, they gave the same velocity (within 20fps). I guess that I wouldn't call that exact proof but that and other observations with other calibers, I would have to say that I have not seen any indicators that would lead me to believe that there were "fast" barrels. You can hit a brick wall before "book" pressures and the resultant velocities are arrived at. When working with the 416 Rem, I had to substitute HDS (Bell) brass as no Rem brass was available. The HDS brass showed extractor marks 6,000psi before arriving at factory pressures. In that case, there was no point in trying to achieve book or factory velocities. So no, you can't just keep dumping in powder until you arrive at the expected velocity. The only time that I hit an indicated pressure wall before the expected velocity, I was working with a wildcat. Pressures were way overboard for the velocities. On examining the barrel, it was found that the barrel maker (intentionally) cut the barrel .002" undersize. As a test, the bullets (Hornadays, in this case) were ring died down to groove diameter and the pressures dropped 18,000psi and all the planets came back into allignment. | |||
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Quote: So the same gun was only used for two barrels.Not much of a test.And what equipment did you use to measure pressures?The fact that two different receivers were used adds another variable which reduces the accuracy of the testing. Quote: Just what I have been saying all along. | |||
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Quote: All of the barrels used by the people printing the manuals are not custom barrels cut to minimum specs.Some are listed as being factory rifles. | |||
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You are correct, of course. | |||
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Is there even such a thing as a SAAMI standard velocity or just a SAAMI pressure standard for a given cartridge?If there is a SAAMI standard velocity,how many barrels does SAAMI use to test each cartridge? | |||
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There is both a pressure and an MV spec for many standard cartridges. The spec for 30-06 covers 110, 130, 150, 165 180 grain bullets, and maybe more. The specs are set using barrels made to SAAMI dimensions. It does not matter how many barrels they use. One is enough. If the dimensions, brass, powder, etc. are the same, the MV will be the same. The model is highly deterministic. The MV does not get to pick what it will be. There is no magic, just physics. If you do things the same, the result will be the same. If you want a different result, you have to do something different. | |||
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Quote: If everything is absolutely identical you are theoretically correct.Unfortunately that would assume that every barrel has exactly the same bore and land diameters,the exact same land width and shape,the exact same rate of twist,the exact same finish and co-efficient of friction,the exact same chamber and throat dimensions,the exact same headspace.The powder would all have to have exactly the same burning rate,the bullets would all have to have exactly the same diameter and have the same hardness and co-efficient of friction of the jacket,the brass would all have to have identical volume and hardness,the primers would all have to have the exact same amount of energy. In other words you are talking about something that is theoretically possible but we all know is not practically possible in the real world.And that is why the actual velocities do vary from barrel to barrel and why printed velocities vary from manual to manual. | |||
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OK, let me put that another way. In an '06 size cartridge, a minimum cut chamber will give you roughly 50-70 fps and 2-3,000 PSI more than an average cut chamber. That is not enough to matter much. A decent machinist can hold tolerances that are tighter than the difference between a medium cut and a minimum cut chamber. So the differences between well made SAAMI test barrels are negligible. They are, for all practical purposes, interchangeable. Remember the story of making 20 identical cartridges, and splitting the lot, testing 10 today, and 10 tomorrow on exactly the same equipment? The random error in the measurement system puts a difference that large into the "just detectable" category. Also remember that barrel temperature is a strong pressure factor, running about 200 PSI per degree F. If your barrel warms from 70 F to 85 F, you'll have as much pressure difference as you will switching from a medium cut chamber to a tight cut chamber. Do you lie awake and fret about your barrel temperature? I don't. I wish SAAMI would spend $50 for a thermocouple, and do all their testing at constant barrel temperature. That would help the data from different labs agree more than any other one thing you could do. What's worrisome are situations like the one mentioned earlier, where the bore was .002" under, and the gun was 18,000 PSI over. That, and reloaders who do not test the exact bullet they are using for max COL, are the things that need attention. On my A Bolt, there is .100" difference between where a Hornady and a Speer bullet engage the lands, and that makes a big difference. | |||
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This is long and interesting. Stubble,There are slow barrels,by that I mean bullets go slow.Even when the primers are falling out!I had a 22" barreled FN 264 that popped primers with Hornady 140 and IMR7828 below max charge and 3050f/s. DuPont's and current Max velocity with IMR7828 is 3117f/s. | |||
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Quote:Excellent post stubblejumper. I read a bit of the "If we assume this is" (times 12-15) fiasco and nearly fell off my chair laughing, as I suspect most who saw it did. I was wondering if anyone was going to be able to stop laughing long enough to call him on it. --- Anyway, I have a Christmas Gift for everyone reading this thread! Ever since the original Oehler M-43 hit the market, I've been interested in them. Once I found out how they worked, I was less enthused. Especially since the very best Pressure Indication Methods "OF ALL TIME" - good old time proven PRE/CHE - are in existance. I've followed with great humor the posts attributing great things to the HSGS which you all should know by now is Reloader's Pyrite(aka Fool's Gold). No one including the salesmen, manufacturers nor the people who drone on and on about how great they are, ever explained how they could be used and Calibrated "properly". That way, they would indeed be useful and shift from a worthless HSGS to a useful SGS. But, here is the BIG Christmas Present: JCN has figured out the correct way to Calibrate a HSGS so it becomes a SGS. I'm not sure how much the straight tapering of the outside of the barrel on his rifle will affect the "built in Fudge Factor" that Irv mentioned in a previous thread, but the good news is it really doesn't matter. JCN's intended HSGS Calibration Procedure will indeed make the SGS worthwhile to those of you who have the HSGSs. I just happened to spot it in a thread on a different Board and all of you should go out of your way to thank him for figuring it out. I've "eluded to it" on numerous threads, but no one ever picked up on what is actually needed. Just ask JCN how he intends to "Calibrate" his HSGS and make it a real useful SGS. Congratulations JCN, you are far ahead of everyone else I've ever seen post about how to "properly use" a Strain Gauge System. Merry Christmas to all of you! | |||
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