In your opinion what would make best military caliber and in what platform?

Yeah, you better include rifle calibers.

I'm going to go with the 55gr M193 cartridge in the M16A1. The very slow twist rate (1-14) stabilized the bullet less than the modern 1-12, 1-9 and 1-7 twist rates. When this semi-stable bullet entered flesh, it tumbled and fragmented and caused massive internal wounds. So massive in fact that NATO refused to standardize it because it was viewed by many as "inhumane." From then on, the NATO and US standard has been the heavier 62gr SS109/M855, which is somehow more humane than a quicker death.

I think on paper the 357 sig was a great cartridge, but somewhere there is a disconnect and its missing its audience. I think the 40 is the best balance between the 9 and 45, and therefor holds the most promise, hence why some 70%+ of LE use the 40 s&w.

For military I think the 5.56 has just about all that can be wrought from a cartridge, I think the 6.8 is a good option, or to dump the idea of the one caliber infantry and have a multi caliber unit, which we are seeing with the designated marksman role, or have different calibers depending on the terrain, like the long reaching 6.8 and 7.62 for afganistan mountains, but 556 in the cities, a switch the 6.8 facilitates.

40 S&W in a DA/SA Sig only because the military would never adopt a Glock with no manual safety. The 40 offers large bore capability in FMJ, high velocity and high capacity. It may be a wee bit more difficult to control, but sometimes its best not to strive for the lowest common denominator.

7mm 08 in AR-10. Long distance and hard hitting. 7mm offers ballistic superiority, and the platform is time tested and modular.

Both will never happen because of existing inventories and NATO standardization, but this is one of those fun questions that asks what if.

In FMJ form? In that case with non-expanding bullets at low velocities, the largest caliber is the most effective, and the .45 ACP proved that it is an effective close range stopper again and again. The platforms that it would be the best in are the handgun, and sub machine gun. It also may make a good personal defense weapon (PDW), but it obviously wouldn't have the capacity of the 5.7x28mm weapons that have been produced to fill that role. In my personal opinion though, until I see some credible proof of the effectiveness of that round, it's just an over-hyped, under-powered varmint cartridge with no place in a military operation.

After years in the military, I have to tell you, the 9mm in the M9 and the 5.56 from the M16A2 the M4 and the SAW seem to work just fine.

30-06 in the M1 Grand. .40 S&W in the Glock.

.45 ACP makes a big hole in FMJ form. It's the best military sidearm cartridge.

Let's fact facts, 6.8 SPC and similar aren't going to be adopted. The new & improved 5.56 M855A1 round will be an improvement in every measurable way over the older M855 round. 5.56 is good at what it was meant to do, and not good at what it wasn't meant to do. Short barrels greatly reduce this round's velocity, we've traded performance for ease of carry/entry/exit..

So, this is my two cents worth.

According to the COD kids the military should exclusively use .50 BMG; so I suppose a derringer in the caliber would be their ideal sidearm.

Mike- I think you have an upset online stalker; change your name and get out while you still can. If it means anything, I gave you a TU.

I was always partial to .45 ACP - but then I'm older.

the .45 acp makes a great caliber in just about any of the glock pistols. they are the most durable autoloading handguns in the world in my opinion.