quote:

Originally posted by kudude:
Dr. K

You can work your problem backwards. According to my ballistic program a 308Win shooting 165gr bullets and 2700fps (factory) produces 2670ftlbs. A 30-06 with 165gr bullet and 2942fps produces 3171ftlbs.

I think you can put aside the idea of a cartridge that will fit the bolt and length of action of the M-4 that will produce 3000fps and 3000ftlbs. It just won't work.

From the aforementioned data, one also can see that your "standard" of 3k fps and 3k ftlbs as it relates to killing power for man or beast is nonsensical. You can kill any man on the planet with a .308 165gr bullet with much less velocity and energy.


I don't know what you are looking for, but the military needs a round that can stop people at very close range who are wearing bullet proof vests. The old M-16 with 62grain bullets developed enough muzzle velocity to penetrate most vest. (1200ftlbs @ muzzle) The M-4's 14.5"barrel doesn't. Contrary to your assertion about the 7.62x39, it produces 1461ftlbs at the muzzle, around 900ftlbs at 200yds and 650ftlbs at 300yds.

It is a ballistic fact that the smaller the hole, the less energy can be imparted to the projectile in a given length of barrel. The only way to get a .223 round to go faster is to have a longer barrel. One can increase the bore size as a means of imparting more energy to the projo, this is why the 6.5, .270 and 7mm bullets fair much better.

The experiences of WWII let the Germans to adopt a shorter, less powerful round for combat in areas which were increasingly "closer."
The Russians rapidly copied it and rifle tailored to it, the SKS. It was rapidly supplanted by the AK. The US adopted the M-14 which was an improved M-1 using new powders to give 30-06 performance in a smaller, lighter round, the 7.62x51. There was really nothing wrong with the M-14 except the M-16 caught the fancy of Sec Def McNamara who want all the services to use the same weapons, uniform, vehicles, etc.

Today, to further enhance its handiness, the M-16's 20" barrel has been shortened and then shortened again to make the M-4. This wasn't a problem when our enemies weren't wearing body armor, but today more and more frequently they are. The M-4's loss of velocity has diminished it ability to take out enemy in close quarter combat and in the desert at extended ranges.

This is the primary beef of grunts in the sandbox and Afghanistan. The secondary gripe is about the vulnerability of the weapon to sand and fouling. This has been "cured" in several modified versions that have gone to a gas system more like the AK's and eliminated the gas tube of the M-4/M-16.

Looking at the terrain we are fighting in, it appears that we need (1) a rifle that is effective at long range for desert and mountain fighting and (2) one that is short for combat in built up areas. Although one cartridge could be designed for both roles, you are going to change barrels or adopted a bullpup design. If you look at the myriad of bullpups being fielded around the world, most have a rifle, carbine and designated marksman model finding that one size fits all doesn't work.

Back to the ballistic conundrum, my 7.62x39 load shoots a 130gr bullet at 2250fps(SKS). I believe that in an 18" tube, I can obtain 2400fps with a 120gr 7mm(.284) bullet with a blown out version of the 39mm case. This would deliver 1660ftlbs at muzzle and just under a 1000ftlbs at 300yds. The .277 and 6.5mm(.264) rounds in 120gr would be slightly slower because of the physics involved (smaller hole), but there would not be a significant difference.

The 7.62x39 Russian case blown out and necked down to 7mm, .270 or 6.5mm would meet the requirements of a cartridge that be deadly at close quarters and reach out 300yds with man-killing energy. There is no need to achieve 3k + 3k. It would defeat much of the rationale of maintain the "mouse" guns on which non-shooters and females particularly can be trained to deliver effective fire in a minimum amount of time.

This is probably more info than you wanted, but I hope it explains the ballistic problem you pose and the futility of pulling criteria for ballistic performance out of thin air. Kudude