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Posted: 5/19/2009 11:58:55 AM EDT
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Oh no not again! lol I'm fairly new to the AR world but have been around guns my whole life. I know the whole 5.56 vs 223 data, etc. After spending much time on this site reading this and that I had come to understand that typically 5.56 is loaded hotter than 223 loadings. I was looking through my newest Midway catalog at the rifle ammo. Funny but I see lots of commercial ammo with 55 grain bullets that show muzzle velocities in the 3200 fps ranges. Now I know the M193 spec(a 5.56 load) calls for velocities in that same range. I also remember reading in the Reloading forum about how one couldn't load up to 5.56 specs since the "special" powder was not "normally" available to reloaders. So I had thought the only way to get to 5.56 velocities was basically to buy preloaded 5.56 ammo. But after seeing all the muzzle velocity numbers in the Midway catalog that got me to wondering about the whole 223 vs 5.56 thing.
I realize a 5.56 chamber is slightly larger than a 223 chamber. That is supposed to allow the use of higher pressure 5.56 round to be fired safely. But if I see commercial ammo that reports muzzle velocities as fast as 5.56 then where are the differences? I know that different powder mixtures might produce different pressures while getting similar velocities. From the looks of it commercially available 223 ammo can match velocities of 5.56 rounds albeit at a higher cost. So is it simply the powder charge, thus higher pressures, in 5.56 that makes it unsafe to use in a 223? Again I had been thinking that only a 5.56 round offered the higher velocities but see that is not necessarily the case. Of course this also could be a cost vs performance thing. 5.56 typically is cheaper to shoot than the equivalent 223 ammo at least for commercially loaded ammo. |
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I'm sort of new to the AR thing myself although I have been loading for my bolt guns for a while.
I realize a 5.56 chamber is slightly larger than a 223 chamber.
My understanding is that the chamber is the same size ( as .223 and 5.56 have the same measurements externally ) It is the throat or lead that is longer to accomodate a heavier ( read longer ) bullet . Please someone correct me if i'm wrong here ! The 5.56 uses a heavier/longer bullet . In a rifle chambered for .223 the ogive of the longer bullet would contact the lands before exiting the neck of the cartridge causing a pressure spike . In a 5.56 chamber ( longer throat ) the bullet would exit the case prior to contacting the lands eliminating the pressure spike. What I'm trying to figure out is this .... If you have an AR chambered for 5.56 can you use .223 brass at 5.56 loads . Mike |
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Quoted:
Oh no not again! lol I'm fairly new to the AR world but have been around guns my whole life. I know the whole 5.56 vs 223 data, etc. After spending much time on this site reading this and that I had come to understand that typically 5.56 is loaded hotter than 223 loadings. I was looking through my newest Midway catalog at the rifle ammo. Funny but I see lots of commercial ammo with 55 grain bullets that show muzzle velocities in the 3200 fps ranges. Now I know the M193 spec(a 5.56 load) calls for velocities in that same range. I also remember reading in the Reloading forum about how one couldn't load up to 5.56 specs since the "special" powder was not "normally" available to reloaders. So I had thought the only way to get to 5.56 velocities was basically to buy preloaded 5.56 ammo. But after seeing all the muzzle velocity numbers in the Midway catalog that got me to wondering about the whole 223 vs 5.56 thing. I realize a 5.56 chamber is slightly larger than a 223 chamber. That is supposed to allow the use of higher pressure 5.56 round to be fired safely. But if I see commercial ammo that reports muzzle velocities as fast as 5.56 then where are the differences? I know that different powder mixtures might produce different pressures while getting similar velocities. From the looks of it commercially available 223 ammo can match velocities of 5.56 rounds albeit at a higher cost. So is it simply the powder charge, thus higher pressures, in 5.56 that makes it unsafe to use in a 223? Again I had been thinking that only a 5.56 round offered the higher velocities but see that is not necessarily the case. Of course this also could be a cost vs performance thing. 5.56 typically is cheaper to shoot than the equivalent 223 ammo at least for commercially loaded ammo. Bro, your missing something very simple here. The 5.56mm velocities (M193) are usually quoted for a 20" barrel. The 223 Remington velocities that you are quoting are from a 24" barrel. |
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Quoted:
Bro, your missing something very simple here. The 5.56mm velocities (M193) are usually quoted for a 20" barrel. The 223 Remington velocities that you are quoting are from a 24" barrel. That would certainly account for some of the differences. I had kinda been thinking that and after I made my post was gonna go back and add that fact as a possibility. |
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Quoted:
I'm sort of new to the AR thing myself although I have been loading for my bolt guns for a while. I realize a 5.56 chamber is slightly larger than a 223 chamber.
My understanding is that the chamber is the same size ( as .223 and 5.56 have the same measurements externally ) It is the throat or lead that is longer to accomodate a heavier ( read longer ) bullet . Please someone correct me if i'm wrong here ! The 5.56 uses a heavier/longer bullet . In a rifle chambered for .223 the ogive of the longer bullet would contact the lands before exiting the neck of the cartridge causing a pressure spike . In a 5.56 chamber ( longer throat ) the bullet would exit the case prior to contacting the lands eliminating the pressure spike. What I'm trying to figure out is this .... If you have an AR chambered for 5.56 can you use .223 brass at 5.56 loads . Mike The throat is longer in the 5.56 chamber to keep pressures lower. Most .223 Remington ammo is loaded with bullets ranging from 45 to 64 grains. Most 5.56 ammo is loaded with 55 or 62 grain bullets. While the 62 grain SS-109 projectile is longer than a regular 62 grain FMJ because of the steel penetrator inserted into the tip, the 55 gr. FMJ bullets used in M193 ammo are not particularly longer or shorter than other 55 grain FMJ bullets. The problem with shooting 5.56 in a .223 chamber does result from the shorter throat, but not because of the length of the bullet. It's because the round is loaded to a higher pressure specification to begin with. As pointed out in another post, the 55 grain 5.56 loads have to reach 3200 fps from a 20" barrel. The load that does that in a 5.56 chamber generates pressure well in excess of SAAMI standards for commercially produced .223 Remington ammunition. The .223 Remington chamber is designed to safely handle the SAAMI pressure standards set forth for .223 Remington ammunition. While most guns are engineered with some margin for safety, the pressure of 5.56 cartridges crowds or exceeds that margin, and while it might not blow up your gun immediately, it will stress it and weaken it. As for using commercial .223 brass to make your own 5.56 ammo, I wouldn't recommend it. In most cases, military brass is thicker, particularly in the webbing and head areas, which is where the pressure is contained, than commercial brass. Best case scenario: You shorten the life of your brass. Worst case scenario: you blow up something important. Somewhere in between there, you get case ruptures, blown out primers, head separations, and all sorts of nasty things that might not ruin you or your gun, but they will ruin your underwear. |
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Quoted:
Quoted:
Bro, your missing something very simple here. The 5.56mm velocities (M193) are usually quoted for a 20" barrel. The 223 Remington velocities that you are quoting are from a 24" barrel. That would certainly account for some of the differences. I had kinda been thinking that and after I made my post was gonna go back and add that fact as a possibility. We used to have people doing chronograph measurements of .223 Vs 5.56 using the same length barrels (20" Vs. 20", 16" Vs. 16", etc) and the .223 always came out slower by 200 - 300 fps or so. |
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