I am looking for a good light to mount to my AR, what lights should I consider?

Malkoff dropin P6 or Solarforce host.

Surefire Fury. EAG version (single output, click tailcap) if they're in stock.  Either the 500 or 1000 lumen version.  Call it a day.

Surefire P2X Fury or P3X Fury.

What's your budget and expected engagement distances?

Streamlight protac hl will fit. 650 lumen, adjustable button programming, $60.

G2X tactical

Surefire G2X tactical is the best low cost/high value light I have found. I have one on my ar 15 in an Elzetta FSB mount. The G2X tactical also has a 1 inch body.

With the exception of maybe the Elzetta, none of those regular flashlights are really weapon lights.
This isn't to say one can't use them as such, I have and probably will again, so have lots of others, but they nearly all
have batteries that bounce back and forth on springs with each shot.  True weapon lights have captured batteries
so this does not happen.  The Elzetta probably are, and Primary Arms Compact Weapon Light does,
I don't know of another plain carry light that does but I'd like to.

Some batteries don't hold up well to such use, or the springs can wear with repeated recoil-use but
it takes quite a bit, especially from a 5.56.  Just know what you're getting into, there is very seldom a free lunch.


All that said, I was very happy with my G2X Tactical in a ring mount the last time I had one for cost vs light.
I'd be sorely tempted to buy an M61 Malkoff (on sale currently for $39) and a L2P Solarforce host right this second.

That's interesting, I guess Surefire and Streamlight do not make real weapons lights because they have springs?

Surefire does, take one apart and you'll see what I mean compared to a 6p or G2, etc.  Never had a Streamlight.
The shock isolating heads like the old M95x had are less of a concern with LED's but the battery slapping
into the LED head is still a thing.  Guys like Malkoff build P60 dropins that are solid enough to take it (I own several) but it's
still a tiny spring for the batteries to whack against.  There are a couple of good pics here https://www.ar15.com/archive/topic.html?b=3&f=20&t=507423  A "real" LED weapon rated light will have batteries that do not reciprocate during recoil, or in the very least do not
move forward into the head/emitter.
I personally think we get away with using regular flashlights on AR's because the recoil is pretty mild.

H

I have Surefire weapon lights with springs in them.  What exact Surefire weapon light are you referring to that does not have any springs in it?  I know what the inside of Surefire lights look like, I have 30-40 of them (all different types and generations) along with many other flashlights.

Are you maybe only referring to the heads that don't have springs?  Almost every tailcap will have a spring in it, even Surefires weapon lights.

Click the link above for a good and similar discussion.  
There is another one here, this isn't a new topic obviously.  http://www.ar15.com/archive/topic.html?b=3&f=20&t=441577
Also, I apologize if I wasn't clear, it isn't the existence of springs so much as it
is the implementation.  It is quite different between a purpose built weapon light and a carry light.  
You should understand what I'm saying about batteries moving back and forth
if you have practically any Surefire weapon light, I know you will if you have an old M95x/Millennium
as you can remove the incan bezel and see that the batteries do not pop out the front unless you remove the
LU60.  It's a great design, if a bit bulky.  Referencing again the above link, I don't have one but it looks like they came up with a cleaner method
for the little scout light since it does not need the shock isolating bezel for the incan bulb.

Again, a "real" weapon light will not let the batteries slam into the head, or into the spring on the head.
Something like a stock 6P or G2, there is nothing but light weight springs holding the batteries on each end,
even more so with many P60 dropins that have questionable spring(and build) quality.
Sticking a flashlight onto a gun does not a weapon light make.
And again, I've done it and will likely do it again, but I believe it's important to know
exactly what one is doing and why with things that go boom.


Edit: I got curious and started Google'ing around and it looks like the mini-scout
started out with no spring on the head at all, and they added one in a later version.  I would
assume this is because a single CR123 is light enough, or they thought it was light enough,
to get away without capturing them.  Neat, but not my preference.  Further reading around it looks like they moved away from
physical forward battery stops when they transitioned to all LED heads, again not my preference.
https://youtu.be/NdAJwjHMkFs