i dont get it. if a 14.5" barrel on the m4 carbine produces a less deadly shot (from what i read on here) how come the government chose that over a barrel that is only 1.5" inches longer?

Because the M4 is supposed to be as compact as possible for CQB while still retaining the ability to engage targets at a longer range. Its not 'less deadly' because its short... Maybe less accurate at a distance.

That less lethal comment only applies to at what range?

You get hit by a 55 grain FMJ at 3,100 fps, it won't matter what barrel length it comes out of as to what it does to you. 3,100 fps is 3,100 fps.

Basically the military has taken a most engagements happen 0-300m philosophy.

The M855 round doesn't fragment very well in any barrel length anyway. They did make the M4 short to be compact for things like room clearing. The average combat distance in Iraq is/was said to be 75 meters or closer. The Mk 262 Mod 1 ammo is said to work well out of the M4 in Afghanistan.



TS

Wikipedia says the original 20" barreled M16 had a muzzle velocity of 3200 fps and the M4s 14.5" barrel has a muzzle velocity of 2900 fps. I am surprised the change in velocity is not more. The 10% change in velocity would cause a close to 20% change in energy (1250 ft/lbs vs 1027 ft/lbs for a 55 grain bullet).

The change from a 20" to a 14.5" barrel reduces the barrel material by over 30% reducing weight and cost.

Urg.

The 14.5" barrel is the shortest barrel that will run reliably with a carbine length gas system and will accommodate both the M203 and standard M9 bayonet (not at the same time obviously).

This post has been edited by KellyTTE: November 21st 2009 4:57 AM

Just for grins, I chronographed some Wolf 62 gr from my Stag 16" and my XP-100 with a 14.5" barrel.
The velocity, at least with the Wolff ammo and from the XP's barrel was 12 fps faster.
BTW, MV was 2772 fps.
I repeated the test a few days later to make sure it was not a fluke or a chrono error. Same results.

Same test with 50 grain bullet in the same firearms gave a more normal disparity for the Stags longer barrel. The Stag was 167 fps faster.
The XP is the overall accuracy champ.

As always, YMMV.

So it got me thinking....more tests in order.
Here are some pics: