Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!cbnews!cbnews!military From: !simnet@ssc-vax (Mark R Poulson) Newsgroups: sci.military Subject: Re: Using the rifle suited to the previous war? Summary: ballistics Message-ID: <1991Jan17.054422.29971@cbnews.att.com> Date: 17 Jan 91 05:44:22 GMT References: <1991Jan5.021828.27885@cbnews.att.com> Sender: military@cbnews.att.com (William B. Thacker) Organization: Boeing Aerospace & Electronics, Seattle WA Lines: 55 Approved: military@att.att.com From: !simnet@ssc-vax (Mark R Poulson) From: Don Newcomb >Subject: Using the rifle suited to the previous war? >From a ballistics point of view, I don't think there is a difference that matters between the NATO cartridges. Compare three cartridges, the NATO 7.62 (aka .308 Win), the Soviet 7.62x39 (AK47 round), and the NATO 5.56 (aka .223 Rem and M-16 cartridge). Round Caliber Projectile weight Muzzle Vel ================================================================= 7.62 NATO .308 147gr ~2900 f/s 7.62x39 .310 125gr ~2300 f/s 5.56 NATO .223 62 or 69gr ~3100 f/s There are two important areas to consider ballistically. First, wounds are usualy much more severe when the bullet strikes its target with a velocity greater than 2100 f/s (the speed of sound in water/flesh). Secondly, bullets drop with range. Both of these points are better with high muzzle velocities and high sectional densities (i.e bullets that are heavy in relation to their caliber). If you look at a ballistics table, you can find the remaining velocity at specific ranges up to 500yds and how far the bullet drops if it was zeroed at a specific range. Both the NATO rounds reduce their velocity to the 2100f/s threshold when they have gone 300 yards. At this point, a bigger hole is slightly more effective, but all shocking capability is lost. The 7.62x39 is already close to the 2100f/s threshold at the muzzle. After 100-150 yards, its just a slow 30 caliber... Bullet drop is minimized when the initial velocity is high. Here, the 5.56 NATO is a definite winner to 400 yards. After this range, bullet drop gets very natsy -- especially with the other 2 calibers. For very long ranges, the 7.62 NATO will have slightly less drop because it has the highest sectional density. But when you're getting bullet drops of 50 to 60 inches, a few inches doesn't seem to matter a whole lot! Bullet drop can be compensentated for with the rifle sights, but the shooter must have a very good range estimate (or keep shooting while aiming higher and higher and higher...). To summarize, the weapon I would NOT want in the desert is something firing the 7.62x39 because if its low muzzle velocity and low sectional density. The 7.62 NATO may be slightly superior in well trained hands at very long ranges when compared to the 5.56 NATO, but I feel the other benefits afforded by the 5.56 NATO cartridge are more relevent (you can carry a lot more ammo and in a lighter rifle). Mark ...uw-beaver!ssc-bee!simnet