Even 100 yards is bad information. 150 years is bad information.  There is an effective range for the M4 weapons system.    500m

You're going to have to define 'Effective Range'.

Range at which a well trained soldier can hit a point target (plastic Ivan)? about 500M

Range at which a well trained soldier can hit an area target (Ivans in a squat formation)? about 800M

Range at which the round can still produce a 'lethal' wound by the old Army Standards (about 70ft-lbs IIRC - the actual figure is in Hatcher's Notebook) so that gives you well over 1000yards.

The range at which the round will fragment? That depends entirely on the round used. For M193 that would be 100y for the 14.5" and about 125y for the 16". Better rounds like the 75gr OTM will extend that to the 150-200y range. Again lots of variables in here.

Range at which YOU can effectively hit the vial zone of a moving target that is taking cover? Expect it to be less than 100y.

Even 100 yards is bad information. 150 years is bad information.  There is an effective range for the M4 weapons system.    500m

Don't be so sure about that number.  The target would have died of old age already, so...... yeah!!   

I've built several AR-15s over the years; some thoughts based on my experience.

For a SHTF rifle, you'll want a chrome lined barrel. (How do you define SHTF?)

Building a accurate AR-15 is easy; float a good barrel.  Really, that's it. 

A good trigger helps, but for a SHTF rifle, reliability is more important than having a whole bunch of adjustments, and anything fitted will wear out sooner than you think.  I like the Rock River Arms 2 stage.

Make sure the gas tube is STRAIGHT in the upper receiver so the key doesn't bind; this may take some fiddling. 

Don't use a torque wrench; anywhere between 30lbs and 80lbs is fine, but the gas tube has to be centered in the hole.

All other things being equal, a 1 in 12 twist will be more accurate with 55gr ball than a 1 in 9 (or 7).  But the 1 in 12 won't fully stabilize 62gr bullets (think 6MOA), and is hopeless with anything heavier.

If you don't shave regularly, you want a fixed stock.  Telescoping stocks pinch.

With a 20" barrel, effective range is around 200yds (before the bullet slows down so much that it doesn't do much damage)   With a 16" barrel, it's more like 50yds.  This isn't an accuracy issue (if anything, shorter barrels are more accurate). it's a velocity issue.

Most optics are useless in heavy rain.  Even ACOGs.  The ELCAN is the only scope I've seen that is still usable with water on the lenses.  Yes, I know it's too big and makes a lightweight AR-15 top heavy.

SNIP

Based on the overall effectiveness, the lighter 5.56 allows you to carry more ammo than the AK ammo .... because you are probably going to need more!! 

Then there is the argument that the AK will keep firing without cleaning for next to infinity, while the DI AR15 needs to be cleaned whenever you take a rest break!  Reliability under less than ideal conditions might be another factor for choosing the AK.

No experience with the ELCAN (too damn expensive), but I will say that my Aimpoints (Comp M4s and T-1s) have been through classes and training in heavy rain and no problems.  Even heavy snow with temps down to around 10 F and no problems, at least with the optic itself.  Yes, they are all 1x optics, but I didn't notice any effects from the rain or snow.  This was for ranges from about 7 yards or so and then out to about 200 yards.  In the same class with heavy snow and freezing temps, another shooter had an Leupold 1-4x and it didn't seem to be negatively affected by the weather. 

Regarding ACOGs, I've shot with them, but mostly in good weather conditions, as in mostly dry.  Why do you feel that they are useless in the rain?  From just water droplets on the lens? 

Yes, I've been out in the rain with an ACOG, trying to see a pig at 50yds or so.  After that experience, I did some tests (getting both lenses covered with drops, dipping in a puddle, etc)  and decided to just stick with iron sights.

As for the "effective" range of a .223; I've shot a lot of pigs over the years, but I've never shot at a person.  I've heard that pigs are harder to put down than any other mammal, so maybe I'm just jaded, but I've had better overall luck with a .30 Carbine (with soft points, every pig has dropped where it was)) than a .223.

Water droplets on any optic can throw your POI WAYYYYY off.  At closer range this may not effect to so much as to miss the target.  But it may have you impacting at an area not intended.. Food for thought.

That is false.

Maximum effective range, for both M4 and M16, have always been 300m.

And most standard Army units assign a designated marksman with a modernized m14 platform at ranges at and beyond 400m, so I'm not sure why your unit(s) are using an M4 at those ranges, unless your unit(s) didn't have the funds to do so.

A well trained and proficient marksman can hit a 1000 yard target with a mosin; still doesn't mean the maximum effective range of that weapon system is 1000 yards.

And as stated, most Army units provide a modernized M14 platform to their best shooters on the platoon/squad level, precisely for the reason that it is a far superior platform for long distance applications as it has a longer maximum effective range.

And before anyone tries to quote FM 3-22.9 in order to prove that the MER is 500m at a point target, let's exercise some common sense. A standard range is set up to 300m for the average soldier. 90% of people on a standardized range have trouble effectively engaging live-action targets at these ranges with an M4, unless they have an optimized optic. And beyond these ranges, only seasoned individuals with lots of trigger time, training and optimized optics can effectively utilize the platform to it's maximal capability. If the true effective range of the M4 platform was beyond 300m, most standardized military ranges would be implementing targets at such ranges.

The average Joe is not going to effectively or efficiently engage targets at ranges beyond 300m with a standard M4 platform, so it really doesn't matter what a book says. This is coming from some of the top shooters in the Army that we had the privilege to train with during the combat rifle marksmanship course.

So should He build it or buy it ?   

Sorry if I took it off topic but Cat's 50 yd comment threw me for a loop. 

So should He build it or buy it ?   

Sorry if I took it off topic but Cat's 50 yd comment threw me for a loop.