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Posted: 1/11/2016 5:13:33 PM EDT
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I have a shipment of AA2460 coming in for my 62gr loads. I looked up load data on Accurate's website. I found data for both 5.56 and .223. The 5.56 loads run well in excess of 60K. When we load for 16in AR's with a 5.56x45 chambers can we go that high? The .223 data is significantly lower. I have included the link. The data I am referring to is on page 24. Any advice on loading 5.56 loads as opposed to .223?
http://www.accuratepowder.com/wp-content/uploads/2010/09/WP_LoadSpec_1-23-14.pdf |
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Load up to 5.56mm cartridge data but use in only 5.56mm chambers. Just about every dimension of a 5.56mm chamber is different than a .233 remington cut chamber and can withstand the increased pressure. Yeah I know that but what I wanted to know was any advice on loading 5.56 loads that are considerably hotter than even the hottest 223 loads. What is the benefit besides extra power? What are the downsides? Sorry for all the questions but none of my reloading manuals have shown the same bullets and same powder side by side with 223 and 5.56. I was actually very surprised and hopeful about running some "a little too hot" .223 loads I have. I am still new at this and trying to read as much as I can, which includes getting advice from other experienced reloaders |
https://www.ar15.com/ammo/ Use facts. Don't listen to bullshit. |
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Not to mention lower pressure makes your brass last a LOT longer. And it only takes one case head failure to ruin your rifle. I wouldn't run 5.56 loads for plinking. I don't even buy 5.56 factory loads for plinking. This goes back to a previous thread that concerned some primer flattening (please lets not get into a long discussion on that) on some 62gr loads that were loaded at probably a grain over max for .223. Then I come across 5.56 data that are well above that. Add to that that my chamber is not a .223 but 5.56, makes me wonder if my "too hot" loads are not as dangerous as I thought. I think one of the problems is that many of the discussions I see on here and other places rarely distinguish between the 2. The distinctions that are made are usually "don't ever run 5.56 rounds in a .223 chamber, but you can run .223 rounds in a 5.56 chamber." But that's usually the only distinctions that are made, And if the load data is so much different between the 2, in my opinion, it would be prudent to make those distinctions in these discussions. Heaven forbid someone has a .223 chamber and uses 5.56 data because they are "they are pretty much the same anyway." Don't get me wrong, I have no desire to run hot loads just for the sake of hot loads especially if I am just plinking with it. But I would like to understand the differences between the 2 loadings. I understand the chamber differences, but how that effects loads is something I'd like to learn. |
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http://i67.tinypic.com/4ifntt.jpg http://i67.tinypic.com/2dk0b9x.jpg https://www.ar15.com/ammo/ Use facts. Don't listen to bullshit. Yes I've seen those in my manuals. I think a lot of the supposed differences in case volume and size is internet myth anyway, but 5.56 chambers are rated for higher pressures than .233 chambers. right? And that drives to the point if this thread. If a load is too hot for a .223 chamber it doesn't mean it is too hot for a 5.56 chamber. Am I right? |
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Yes I've seen those in my manuals. I think a lot of the supposed differences in case volume and size is internet myth anyway, but 5.56 chambers are rated for higher pressures than .233 chambers. right? And that drives to the point if this thread. If a load is too hot for a .223 chamber it doesn't mean it is too hot for a 5.56 chamber. Am I right? Quoted:
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http://i67.tinypic.com/4ifntt.jpg http://i67.tinypic.com/2dk0b9x.jpg https://www.ar15.com/ammo/ Use facts. Don't listen to bullshit. Yes I've seen those in my manuals. I think a lot of the supposed differences in case volume and size is internet myth anyway, but 5.56 chambers are rated for higher pressures than .233 chambers. right? And that drives to the point if this thread. If a load is too hot for a .223 chamber it doesn't mean it is too hot for a 5.56 chamber. Am I right? The chambers are made of the same steel. Think about that. |
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The chambers are made of the same steel. Think about that. Quoted:
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http://i67.tinypic.com/4ifntt.jpg http://i67.tinypic.com/2dk0b9x.jpg https://www.ar15.com/ammo/ Use facts. Don't listen to bullshit. Yes I've seen those in my manuals. I think a lot of the supposed differences in case volume and size is internet myth anyway, but 5.56 chambers are rated for higher pressures than .233 chambers. right? And that drives to the point if this thread. If a load is too hot for a .223 chamber it doesn't mean it is too hot for a 5.56 chamber. Am I right? The chambers are made of the same steel. Think about that. The same steel doesn't mean that it can endure the same pressure. |
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The glitch is finding reliable 5.56 loading data, bases on available canister powders to begin with,
Hence most published loads are for 223 Saami at 55K Max working pressure, while 5.56 Nato would be 62K PSI max instead. Looking at Noslers data for 5.56 loads, they are still using the Saami 55K PSI as the cap for max pressure, instead of 63K PSI instead. |
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You guys are missing the point.
Accurate Data is at 62K tested in a 5.56 Chamber, not a 223 chamber. So forget the chamber differences as they are irrelevant to this discussion. The question is, will a AR-15 handle Real Life 62K Chamber Pressures and still hold up. Well, lets look at a few other cartridges chambered in an AR-15, shall we. SAAMI Max Average Pressures (MAP) 223 Rem = 55K psi 6.5 Grendel = 52K psi 7.62 x 39 = 45K psi 30 Rem AR = 55K psi 300 Blackout = 55K psi Now, lets axe ourselves this here simple question, " If every cartridge that is chambered in a AR-15 Type rifle runs at 55K psi Max or Less, why does the 5.56 get a pass and is allowed to safely run at 62K psi"? " Why can we not load the Grendel and the X 39 and Blackout to the same 62K psi Pressures"? Same rife, same steel, same everything, cept what? What makes it safe to ruin a 5.56 at 62K when NO other Cartridge can safely do that in an AR Platform? Lengthening the Throat? NO, double NO! Lengthening the throat will reduce pressures of of an existing load, yes. By lengthening the throat, we can increase the powder charge and bring the "Chamber Pressures" back up to MAP, but we cannot safely increase the charge to where MAP is above and beyond safe MAP. Accurate 5.56 load data is in error for the AR Type Platform. . |
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Steve, I think you missed one vital point.
With the exception of 300blk the variants you listed have a larger case head diameter. When you keep pounds PER SQUARE INCH the same and you increase the surface area you get more force acting on the bolt. So you can't run 6.8, 6.5, or 7.62x39 at 62k psi and have the same longevity on parts as 5.56. |
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The difference is
$.03 cents in my town. 
Actually the higher pressures are allowed because the .mil knows it needs more smash out of the round while the GC restricts the ammo type. So to get more velocity they stretch the 5.56 as hard as they can. The .mil is not worried about longevity of the bolt/barrel they just r2 them at set intervals. |
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Ya might want to read this.
http://thefiringline.com/forums/showthread.php?t=553455&highlight=56 Caution: Do not use the Western Powders load data for 5.56×45 without a lot of careful consideration I was very surprised to see the separate 5.56 loads in the Western load data. That data constitutes a significant misunderstanding. After seeing it, I called Western Powders yesterday afternoon and explained what I am about to explain here. The response of the technician I spoke with was “Oh”; and then, “I’ll pass that along.” There is no difference in absolute pressure between .223 Remington and 5.56 NATO. None! The two different Maximum Average Pressure (MAP) standards are artifacts of the different measuring instrumentation used here and in the CIP. The same lot of reference cartridges put in a SAAMI or a Lake City conformal transducer that gives readings averaging 55,000 psi will give readings averaging 62,366 psi in European channel transducers. This why the U.S. military and SAAMI specs have a maximum average pressure (MAP) of 55,000 psi and the Europeans have a MAP of 62,366 psi (actually, 4300 bar in their units). The European EVPAT 7.62 and 5.56 test procedures are based on results of their measurements of reference ammunition made in the U.S. using the U.S. test procedures, SCATP 7.62 and 5.56 for NATO compatible ammunition. |
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Steve, I think you missed one vital point. With the exception of 300blk the variants you listed have a larger case head diameter. When you keep pounds PER SQUARE INCH the same and you increase the surface area you get more force acting on the bolt. So you can't run 6.8, 6.5, or 7.62x39 at 62k psi and have the same longevity on parts as 5.56. Hence the reason the Grenel and the 7.62x39 are below 55K psi. Case head aside, Why can we not run a 223 or a BO at 62K psi only the 5.56? |
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Ya might want to read this. http://thefiringline.com/forums/showthread.php?t=553455&highlight=56 Caution: Do not use the Western Powders load data for 5.56×45 without a lot of careful consideration I was very surprised to see the separate 5.56 loads in the Western load data. That data constitutes a significant misunderstanding. After seeing it, I called Western Powders yesterday afternoon and explained what I am about to explain here. The response of the technician I spoke with was “Oh”; and then, “I’ll pass that along.” There is no difference in absolute pressure between .223 Remington and 5.56 NATO. None! The two different Maximum Average Pressure (MAP) standards are artifacts of the different measuring instrumentation used here and in the CIP. The same lot of reference cartridges put in a SAAMI or a Lake City conformal transducer that gives readings averaging 55,000 psi will give readings averaging 62,366 psi in European channel transducers. This why the U.S. military and SAAMI specs have a maximum average pressure (MAP) of 55,000 psi and the Europeans have a MAP of 62,366 psi (actually, 4300 bar in their units). The European EVPAT 7.62 and 5.56 test procedures are based on results of their measurements of reference ammunition made in the U.S. using the U.S. test procedures, SCATP 7.62 and 5.56 for NATO compatible ammunition. Never heard this before. Let me make sure I get what you are saying. Is the 62k and the 55k then just something like metric and standard? In other words if a load producing 55k in the new measure was measured in the older measure would it be 62k? |
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Ya might want to read this. http://thefiringline.com/forums/showthread.php?t=553455&highlight=56 Caution: Do not use the Western Powders load data for 5.56×45 without a lot of careful consideration I was very surprised to see the separate 5.56 loads in the Western load data. That data constitutes a significant misunderstanding. After seeing it, I called Western Powders yesterday afternoon and explained what I am about to explain here. The response of the technician I spoke with was “Oh”; and then, “I’ll pass that along.” There is no difference in absolute pressure between .223 Remington and 5.56 NATO. None! The two different Maximum Average Pressure (MAP) standards are artifacts of the different measuring instrumentation used here and in the CIP. The same lot of reference cartridges put in a SAAMI or a Lake City conformal transducer that gives readings averaging 55,000 psi will give readings averaging 62,366 psi in European channel transducers. This why the U.S. military and SAAMI specs have a maximum average pressure (MAP) of 55,000 psi and the Europeans have a MAP of 62,366 psi (actually, 4300 bar in their units). The European EVPAT 7.62 and 5.56 test procedures are based on results of their measurements of reference ammunition made in the U.S. using the U.S. test procedures, SCATP 7.62 and 5.56 for NATO compatible ammunition. If that is true, then why are there higher powder loads in the 5.56? Significantly higher. It seems to me that if the .223 load produces 55k with 25.0 grains of powder, then the 5.56 loaded with 27.4 would produce more than 55k. Also my Horn9 has a completely separate section for 5.56 loads with much higher powder measures. Again, not trying to be argumentative, just trying to make sure I am understanding your point. |
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If that is true, then why are there higher powder loads in the 5.56? Significantly higher. It seems to me that if the .223 load produces 55k with 25.0 grains of powder, then the 5.56 loaded with 27.4 would produce more than 55k. Also my Horn9 has a completely separate section for 5.56 loads with much higher powder measures. Again, not trying to be argumentative, just trying to make sure I am understanding your point. Quoted:
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Ya might want to read this. http://thefiringline.com/forums/showthread.php?t=553455&highlight=56 Caution: Do not use the Western Powders load data for 5.56×45 without a lot of careful consideration I was very surprised to see the separate 5.56 loads in the Western load data. That data constitutes a significant misunderstanding. After seeing it, I called Western Powders yesterday afternoon and explained what I am about to explain here. The response of the technician I spoke with was “Oh”; and then, “I’ll pass that along.” There is no difference in absolute pressure between .223 Remington and 5.56 NATO. None! The two different Maximum Average Pressure (MAP) standards are artifacts of the different measuring instrumentation used here and in the CIP. The same lot of reference cartridges put in a SAAMI or a Lake City conformal transducer that gives readings averaging 55,000 psi will give readings averaging 62,366 psi in European channel transducers. This why the U.S. military and SAAMI specs have a maximum average pressure (MAP) of 55,000 psi and the Europeans have a MAP of 62,366 psi (actually, 4300 bar in their units). The European EVPAT 7.62 and 5.56 test procedures are based on results of their measurements of reference ammunition made in the U.S. using the U.S. test procedures, SCATP 7.62 and 5.56 for NATO compatible ammunition. If that is true, then why are there higher powder loads in the 5.56? Significantly higher. It seems to me that if the .223 load produces 55k with 25.0 grains of powder, then the 5.56 loaded with 27.4 would produce more than 55k. Also my Horn9 has a completely separate section for 5.56 loads with much higher powder measures. Again, not trying to be argumentative, just trying to make sure I am understanding your point. Accurate data is the only place you will see 62K psi load data, all other load data is at or below 55K psi. Lets look at some "Factory" 223 vs 5.56 ammunition, then decide if 5.56 is inded loaded to higher pressures. http://www.midwayusa.com/product/2900355842/winchester-usa-ammunition-q3131-556x45mm-nato-55-grain-full-metal-jacket Technical Information Caliber: 5.56x45 (223 Remington) Bullet Weight: 55 Grain Bullet Style: Full Metal Jacket Case Type: Brass Ballistics Information: Muzzle Velocity: 3240 fps Muzzle Energy: 1282 ft. lbs. http://www.midwayusa.com/product/2900275599/winchester-usa-ammunition-223-remington-55-grain-full-metal-jacket Technical Information Caliber: 223 Remington Bullet Weight: 55 Grain Bullet Style: Full Metal Jacket Case Type: Brass Ballistics Information: Muzzle Velocity: 3240 fps Muzzle Energy: 1282 ft. lbs Note: Same Bullet, Same Manufacturer, Same velocity. Same velocity = Same pressures. Here is another example, this time they are both Federal 62gr FMJ. http://www.midwayusa.com/product/789567/federal-ammunition-556x45mm-nato-62-grain-xm855-ss109-penetrator-full-metal-jacket-10-round-clips-in-ammunition-can-of-420-14-boxes-of-30 Federal Ammunition 5.56x45mm NATO 62 Grain XM855 SS109 Penetrator Full Metal Jacket Technical Information Caliber: 5.56x45mm NATO Bullet Weight: 62 Grains Bullet Style: SS109 FMJ Penetrator Case Type: Brass Ballistics Information: Muzzle Velocity: 3020 fps Muzzle Energy: 1256 ft lbs http://www.midwayusa.com/product/528001/federal-american-eagle-ammunition-223-remington-62-grain-full-metal-jacket-box-of-20 Technical Information Caliber: 223 Remington Bullet Weight: 62 Grains Bullet Style: Full Metal Jacket Boat-Tail Case Type: Brass Ballistics Information: Muzzle Velocity: 3020 fps Muzzle Energy: 1255 ft. lbs. Again same manufacturer, same bullet, Identical Velocities. Identical velocities = Identical pressure, so, they are indeed the same identical round. Not just "similar" identical. |
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Never heard this before. Let me make sure I get what you are saying. Is the 62k and the 55k then just something like metric and standard? In other words if a load producing 55k in the new measure was measured in the older measure would it be 62k? Quoted:
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Ya might want to read this. http://thefiringline.com/forums/showthread.php?t=553455&highlight=56 Caution: Do not use the Western Powders load data for 5.56×45 without a lot of careful consideration I was very surprised to see the separate 5.56 loads in the Western load data. That data constitutes a significant misunderstanding. After seeing it, I called Western Powders yesterday afternoon and explained what I am about to explain here. The response of the technician I spoke with was “Oh”; and then, “I’ll pass that along.” There is no difference in absolute pressure between .223 Remington and 5.56 NATO. None! The two different Maximum Average Pressure (MAP) standards are artifacts of the different measuring instrumentation used here and in the CIP. The same lot of reference cartridges put in a SAAMI or a Lake City conformal transducer that gives readings averaging 55,000 psi will give readings averaging 62,366 psi in European channel transducers. This why the U.S. military and SAAMI specs have a maximum average pressure (MAP) of 55,000 psi and the Europeans have a MAP of 62,366 psi (actually, 4300 bar in their units). The European EVPAT 7.62 and 5.56 test procedures are based on results of their measurements of reference ammunition made in the U.S. using the U.S. test procedures, SCATP 7.62 and 5.56 for NATO compatible ammunition. Never heard this before. Let me make sure I get what you are saying. Is the 62k and the 55k then just something like metric and standard? In other words if a load producing 55k in the new measure was measured in the older measure would it be 62k? Not exactly, the difference has to do with the "position" of the transducer. In the CIP the transducer is located further forward compared to SAAMI, thus giving a higher reading than SAAMI with identical ammo. |
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Even Black Hills Factory 223 and 5.56 Ammunition are identical. http://www.midwayusa.com/product/1339912049/black-hills-ammunition-556x45mm-nato-77-grain-sierra-matchking-hollow-point http://www.midwayusa.com/product/1339114847/black-hills-remanufactured-ammunition-223-remington-77-grain-sierra-matchking-hollow-point-boat-tail-box-of-50 But again, the "5.56" load data has much higher powder loads than the .223" does. No way will they have the same pressure, velocity or energy. Doesn't matter who publishes it. |
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But again, the "5.56" load data has much higher powder loads than the .223" does. No way will they have the same pressure, velocity or energy. Doesn't matter who publishes it. Quoted:
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Even Black Hills Factory 223 and 5.56 Ammunition are identical. http://www.midwayusa.com/product/1339912049/black-hills-ammunition-556x45mm-nato-77-grain-sierra-matchking-hollow-point http://www.midwayusa.com/product/1339114847/black-hills-remanufactured-ammunition-223-remington-77-grain-sierra-matchking-hollow-point-boat-tail-box-of-50 But again, the "5.56" load data has much higher powder loads than the .223" does. No way will they have the same pressure, velocity or energy. Doesn't matter who publishes it. Show me actuall 5.56 62K pressure data other that Accurate/Ramshot? Again, Accurate Ramshot (Western) Powders 5.56 load data is the ONLY 5.56 62K data anywhere. It is in error. Here is Nosler 223 vs 5.56 load data. http://www.nosler.com/nosler-load-data/223-remington/ http://www.nosler.com/nosler-load-data/556x45-nato/ Note the 223 with heavy bullets is identical to the 5.56 with same heavy bullets. NO increase in Powder from 223 to 5.56. Neither Lyman, Hodgdon, Alliant, Vihtavuori, or ADI list the 5.56 seperatly from the 223. All data is 223, Accurate,Ramshot is the only one and as pointed out in the link above, should be used with extreme caution, or better yet, avoided. |
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Ya might want to read this. [snip] Quoted:
Ya might want to read this. [snip] All of this assumes that one of the largest powder distributors in the USA are too ignorant to understand the difference between SAAMI and CIP pressure standards. I doubt very sincerely that is the case. They specify directly in the load data that it is loaded to "CIP" standards. Assuming arguendo that the quoted source is correct "There is no difference in absolute pressure between .223 Remington and 5.56 NATO. None! ": That absolutely does NOT mean that 223 and 5.56 load data will be the same. 5.56 has a chamber designed in a way which reduces peak pressure all other things being equal. Therefore in order to create a full pressure load FOR A RIFLE WITH A 5.56 CHAMBER one must necessarily pressure test that load in a 5.56 chamber and NOT a 223 chamber. And it is therefore no surprise at all that the 5.56 load data ends up with higher powder charges and higher velocity. Whether AA actually simply used SAAMI spec test equipment and simply bumped the pressure limit? I have no idea, and I don't intend to find out. You are preaching to the choir. You'll notice that I'm the guy in one of the first responses to this thread who advised to just use 223 data and leave it at that. ETA: and while SOME manufacturers might load 223 and 5.56 the same it is very clear that all do NOT: http://www.hornady.com/store/5.56-NATO-75-gr-BTHP-Superformance-Match/ http://www.hornady.com/store/223-Rem-75-gr-bthp-Superformance-match/ Take a close look at the velocity figures paying particular attention to the test bbl length. One would guess that ammo tested in a 24" barrel would be 100fps faster than ammo tested in a 20" barrel if the load was the same, but obviously that is not the case here. And in fact what we find when tested side by side is that Hornady NATO spec ammo produces substantially higher velocity than 223 spec ammo in the same firearm: http://www.ar15.com/forums/t_3_16/283506_.html http://www.americanrifleman.org/articles/2013/3/4/223-remington-vs-556-whats-in-a-name/ According to Jeff Hoffman, the owner of Black Hills Ammunition, military ammunition can be expected to hit 60,000 p.s.i.,?if measured on a Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) mid-case system. Black Hills loads both 5.56x45 mm and .223 Rem., and Hoffman was a tremendous help in researching this article. He also provided these pressure specifications for the cartridges. The .223 Rem. mid-case transducer maximum average pressure is 55,000 p.s.i., while a 5.56x45 mm measured with a case mouth transducer has a maximum average pressure of 58,700 p.s.i. |
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Yes I've seen those in my manuals. I think a lot of the supposed differences in case volume and size is internet myth anyway, but 5.56 chambers are rated for higher pressures than .233 chambers. right? And that drives to the point if this thread. If a load is too hot for a .223 chamber it doesn't mean it is too hot for a 5.56 chamber. Am I right? Quoted:
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http://i67.tinypic.com/4ifntt.jpg http://i67.tinypic.com/2dk0b9x.jpg https://www.ar15.com/ammo/ Use facts. Don't listen to bullshit. Yes I've seen those in my manuals. I think a lot of the supposed differences in case volume and size is internet myth anyway, but 5.56 chambers are rated for higher pressures than .233 chambers. right? And that drives to the point if this thread. If a load is too hot for a .223 chamber it doesn't mean it is too hot for a 5.56 chamber. Am I right? Military cases in 5.56mm are no different in volume (in general) from commercial .223 Remington cases. In .308/7.62x51, there IS a difference, but NOT in 5.56. The "chamber" difference between 5.56 and .223 is ALL in the throat of the chamber - the NATO chamber has a longer, less abrupt leade than the SAAMI .223 Remington chamber. There are real differences in how the two chambers handle pressures BECAUSE OF THE LEADE, not because of the case section of the chamber, the way the steel is treated, or anything else. Further, the NATO round's maximum pressure is measured at a different place, with a completely different measurement system from the SAAMI round, and there is no way to come up with an equivalence between the two. Sadly, pressure test barrels and the equipment to measure pressure with them are VERY expensive compared to the equipment even an advanced handloader has, so it's not likely that anyone is going to run out and do comparative tests with the two rounds in both test setups, so until someone with deep pockets decides to enlighten the masses (that's us), it's safest to think of the two different loadings as different enough to keep straight. |
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You guys are missing the point. Accurate Data is at 62K tested in a 5.56 Chamber, not a 223 chamber. So forget the chamber differences as they are irrelevant to this discussion. The question is, will a AR-15 handle Real Life 62K Chamber Pressures and still hold up. Well, lets look at a few other cartridges chambered in an AR-15, shall we. SAAMI Max Average Pressures (MAP) 223 Rem = 55K psi 6.5 Grendel = 52K psi 7.62 x 39 = 45K psi 30 Rem AR = 55K psi 300 Blackout = 55K psi Now, lets axe ourselves this here simple question, " If every cartridge that is chambered in a AR-15 Type rifle runs at 55K psi Max or Less, why does the 5.56 get a pass and is allowed to safely run at 62K psi"? " Why can we not load the Grendel and the X 39 and Blackout to the same 62K psi Pressures"? Same rife, same steel, same everything, cept what? What makes it safe to ruin a 5.56 at 62K when NO other Cartridge can safely do that in an AR Platform? Lengthening the Throat? NO, double NO! Lengthening the throat will reduce pressures of of an existing load, yes. By lengthening the throat, we can increase the powder charge and bring the "Chamber Pressures" back up to MAP, but we cannot safely increase the charge to where MAP is above and beyond safe MAP. Accurate 5.56 load data is in error for the AR Type Platform. |
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This has been a good discussion and helpful to me. My conclusion. I have no reason to run 5.56 loads for my plinking ammo, so i won't. However I might work up some 75gr with 5.56 loads that I have in my Horn 9 just for educational purposes This is exactly what I do. My 55gr blasting loads are middle of the road .223 loads. Nothing more needed. My 62gr TSX hunting loads are much hotter and most likely get close to 5.56 pressures but not the full 62k we often see quoted. |
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There should be no problem with a "real life" AR with a true 5.56mm NATO chamber handling actual 5.56mm pressures. It's not about anything except the chamber leade. Quoted:
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You guys are missing the point. Accurate Data is at 62K tested in a 5.56 Chamber, not a 223 chamber. So forget the chamber differences as they are irrelevant to this discussion. The question is, will a AR-15 handle Real Life 62K Chamber Pressures and still hold up. Well, lets look at a few other cartridges chambered in an AR-15, shall we. SAAMI Max Average Pressures (MAP) 223 Rem = 55K psi 6.5 Grendel = 52K psi 7.62 x 39 = 45K psi 30 Rem AR = 55K psi 300 Blackout = 55K psi Now, lets axe ourselves this here simple question, " If every cartridge that is chambered in a AR-15 Type rifle runs at 55K psi Max or Less, why does the 5.56 get a pass and is allowed to safely run at 62K psi"? " Why can we not load the Grendel and the X 39 and Blackout to the same 62K psi Pressures"? Same rife, same steel, same everything, cept what? What makes it safe to ruin a 5.56 at 62K when NO other Cartridge can safely do that in an AR Platform? Lengthening the Throat? NO, double NO! Lengthening the throat will reduce pressures of of an existing load, yes. By lengthening the throat, we can increase the powder charge and bring the "Chamber Pressures" back up to MAP, but we cannot safely increase the charge to where MAP is above and beyond safe MAP. Accurate 5.56 load data is in error for the AR Type Platform. So how does lengthening the lead Authorize an increase in pressure from 55K to 62K? With your logic, we should be able to take any SAAMI spec chamber, like the 6.5 Grendel, open up the throat then take the Grendel's 52K psi Max and extend that to 62 or even 65K psi.without issues. What the hell was Bill Alexander thinking? All those years of testing, broken rifles, broken bolts and all he had to was open up the throat to allow for a 62+ MAP. Guess he screwed up , Huh? |
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So how does lengthening the lead Authorize an increase in pressure from 55K to 62K? With your logic, we should be able to take any SAAMI spec chamber, like the 6.5 Grendel, open up the throat then take the Grendel's 52K psi Max and extend that to 62 or even 65K psi.without issues. What the hell was Bill Alexander thinking? All those years of testing, broken rifles, broken bolts and all he had to was open up the throat to allow for a 62+ MAP. Guess he screwed up , Huh? The Grendel is a different subject. I'm hardly going to question Bill Alexander; he's a designer, and I'm a hobbyist. And he's a nice guy too, so I'm certainly not going to dis him. We're talking about the difference between two physically identical cartridges with different pressure maxima - which are measured in different locations in the test barrel, and which are measured with different systems that are not convert-able to each other,though the NATO system is similar to the CIP system used in Europe. The longer leade, which includes a longer freebore and a less steep angle at the onset of the rifling allows the bullet to start moving a bit more before it engages the rifling. Combined with the DIFFERENT measurement systems and locations, the NATO chamber is better suited for tolerating the "higher pressures" of the NATO round. Keep in mind that the SAAMI chamber spec was designed for bolt action rifles, not magazine fed, semi- and full-automatic rifles. I personally think that there is no "real" difference between SAAMI specs and NATO specs because of the differences in location and measurement systems. Read this article for some more details on the "differences." |
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