I'm going to buy the Midwest Industries handguard that extends the length 2.2"... so right up to the back of the flash hider.  Do I get the Primary Arms light + mount that is optional and discounted with the purchase of the handguard, or do I go with something else?  I'm told the bezel of the light will get some residue on it if I go this route.

I use the TLR-HL with Long gun kit.  With the right muzzle device, it helps keep carbon residue to a minimum.

If you are going with a light that will mount inside the handguard, don't buy the Primary Arms light.  You want to get something that will allow you to load the batteries from the front, or you will have to remove the entire flashlight and mount just to change the batteries.

Manticore used to sell the Solarforce lights, specifically the L2M, and it has worked great for me.  It will take any light module built for a P60 and can hold either 1 or 2 123A batteries.  Don't let the name fool you, Solarforce makes great lights.  The key is using a good lamp assembly from Cree/Surefire/etc.

L2M Light body:
https://www.amazon.com/Solarforce-Black-L2M-Flashlight-Body/dp/B00NCB4WJO/ref=sr_1_5?m=A1GHBXAJ5YNWTU&s=merchant-items&ie=UTF8&qid=1506865720&sr=1-5&refinements=p_4%3ASolarforce

PTS-4 Remote Switch:
https://www.amazon.com/Solarforce-PTS-4-remote-switch/dp/B00NB84TBO/ref=sr_1_11?m=A1GHBXAJ5YNWTU&s=merchant-items&ie=UTF8&qid=1506865720&sr=1-11&refinements=p_4%3ASolarforce

I am a big fan of simple, reliable, and as cheap as I can get those 2.
My rifles use the vtac light mount with a Surefire G2X tactical.

Interesting choice...   IDK if I would trust my life to a system I put together though.  That is a good point though about being able to change batteries through the front.  

That looks like one of the XL handguards (longest one MI makes)... what barrel length is that?



Do you know if 4sevens still makes a weapon light?  It used to be called the Maelstrom, and came with a pressure switch.  I find other lights with a similar name on their site, but the one I'm thinking of apparently is no longer made.  I wonder if that one would have fit the MI mount... and I wonder if batteries were/are accessible from the front.

you mean an externally mounted light?  on a rail?  that's always an option, too.  If I go external, I may try out an Inforce. However, I'd like them to make an M-lok variant rather than needed a rail adapter.  

Looks good.  What handguard length and barrel length is that?
I didn't consider running a wire across the top of the handguard... interesting.

It is an 18" barrel.  

I have never heard of 4sevens.

16", and the one MI says is appropriate for 16" barrels.  The other one (seen in this thread) is too long and will not work well with most muzzle devices, and is designed for 18" barrels.

ETA:  I didn't think of a wire across the top either, a buddy of mine who knows more about tactical stuff figured that out.  But it was a good solution to all that wire, getting it out of the way of the CH, away from the barrel.  The 12 o clock position didn't work with the tail inlet on the light body vs. the amount of rail space required, hence the 2 o clock offset.