wrillo Posted April 2, 2009 Report Share Posted April 2, 2009 So, like I said in another thread, I know nothing about guns. So I decided to start reading about calibres on wikipedia. I'm not sure if wiki is wrong or written poorly or I'm just interpreting it wrong.Metric calibres for small arms are usually expressed with an "x" between the width and the length; for example, 7.62x51 NATO. This indicates that the cartridge uses a 7.62 mm diameter bullet, loaded in a case 51 mm long. Similarly, the 6.5x55 Swedish cartridge has a bullet of 6.5 mm and a case length of 55 mm. The means of measuring a rifled bore varies, and may refer to the diameter of the lands or the grooves of the rifling; this is why the .303 British, measured across the lands, actually uses a .311 inch bullet (7.70 mm vs. 7.90 mm), while the .308 Winchester, while dimensionally similar to (but should not be considered interchangeable with) the 7.62x51 mm NATO cartridge, is measured across the grooves and uses a .308" diameter (7.62 mm) bullet. An exception to this rule are the proprietary cartridges used by U.S. maker Lazzaroni, which are named based on the groove diameter in millimeters, such as the 7.82 Warbird.The above article says they should not be considered interchangable, why? The .308 Win was made to be the civilian version of the 7.62, right? The article on the .308 Win even says:The .308 Winchester is a rifle round and is the commercial version of the military 7.62x51mm NATO centerfire cartridge.So what are the differences? Quote Link to comment Share on other sites More sharing options...
flounder Posted April 2, 2009 Report Share Posted April 2, 2009 (edited) I have posted this same response before when the 5.56 vs .223 question was asked. It has to do with different chambers and pressures for the round. At one time there was a bit of difference in cartridge lenght between the .308 and 7.62x51 however, now, the case dimensions are the same. Winchester and the US influenced NATO to move to the .308 as the std round. But... they changed the designation to the std decimal 7.62 x 51. Although the dies and in most cases, the OAL is the same, there are some pressure differences that make the rounds different. (OAL = Overall Lenght)These days, both are interchangeable. Read here for unsafe cartridge defs. http://www.saami.org/Unsafe_Combinations.cfm Edited April 2, 2009 by flounder Quote Link to comment Share on other sites More sharing options...
wrillo Posted April 2, 2009 Author Report Share Posted April 2, 2009 Okay, yeah I was reading about 5.56 and .223 and why it was safe to use .223 in 5.56 but not the other way around. So, because the .308 produces higher pressure 5.56 is safe in a .308 but not necessarily the other way around?oh and what is OAI? google doesn't know that one lolthanks Quote Link to comment Share on other sites More sharing options...
flounder Posted April 2, 2009 Report Share Posted April 2, 2009 Okay, yeah I was reading about 5.56 and .223 and why it was safe to use .223 in 5.56 but not the other way around. So, because the .308 produces higher pressure 5.56 is safe in a .308 but not necessarily the other way around?oh and what is OAI? google doesn't know that one lolthanksIts OAL I changed it.. Overall Length.. NEVER shoot 5.56 in a .308... 7.62x51 is ok. Also, the higher pressure issue only comes into play when loading at max loads or above. Quote Link to comment Share on other sites More sharing options...
wrillo Posted April 2, 2009 Author Report Share Posted April 2, 2009 oops! yeah, I meant 7.62 Quote Link to comment Share on other sites More sharing options...
flounder Posted April 2, 2009 Report Share Posted April 2, 2009 oops! yeah, I meant 7.62Make sure its 7.62x51 and not 7.62x (39,42,54) etc. Quote Link to comment Share on other sites More sharing options...
wrillo Posted April 2, 2009 Author Report Share Posted April 2, 2009 Make sure its 7.62x51 and not 7.62x (39,42,54) etc.check Quote Link to comment Share on other sites More sharing options...
John Posted April 2, 2009 Report Share Posted April 2, 2009 Okay, yeah I was reading about 5.56 and .223 and why it was safe to use .223 in 5.56 but not the other way around. like flounder said, pressure. same kinda deal with a .357 and a .38a .357 is more powerful than a .38. you can shoot a .38 in a .357, but not the other way around. in fact, IIRC they purposefully made the .357 cartridge a tad bit longer so that you cant accidentally put it into a .38 Quote Link to comment Share on other sites More sharing options...
speedytriple Posted April 3, 2009 Report Share Posted April 3, 2009 Since we are talking ballistics, what is the diffrence between .45acp and .45gap? Quote Link to comment Share on other sites More sharing options...
flounder Posted April 3, 2009 Report Share Posted April 3, 2009 Since we are talking ballistics, what is the diffrence between .45acp and .45gap?Google is your friend. http://home.comcast.net/~petej/compare.45acp.45gap.htm Quote Link to comment Share on other sites More sharing options...
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