For the money the Streamlight Protac 2 is really hard to beat. Comes with pressure pad and mounts to put the pad on a Picatanny rail.
https://www.amazon.com/Streamlight-88059-Railmount-Dedicated-Fixed-Mount/dp/B01AXR8IKS/
Amazon has it for $102 with 15% off if you check the coupon box below the price.
Streamlight ProTac Rail Mount 2.
625 lumens. It's bright as heck and comes with a pressure plate.
$100 on Amazon. Don't waste your money with other overpriced brands.
this streamlight is also a good choice I run them on all my rifles, no issues. Comes with all the hardware you need and even zip ties for cable management
It might be a Streamlight ProTac. They sell them on amazon for cheap with a pressure switch and 2 ways to mount them (rail adapter and sticky tape) also comes with 2 batteries. It’s what i run on my rifle and have had 0 issues over the last 2 years
Looks like the price dropped even more on the Streamlight Protac Rail Mount 2 on Amazon, only $107 shipped now:
https://www.amazon.com/dp/B01AXR8IKS/ref=cm_sw_r_cp_apa_i_0A7sFbV6Z0BKC
I have this and multiple HLX, this is the 625 lumen but still plenty bright, and not quite as chunky as the HLX.
Looks like amazon has it for $118
Streamlight 88059 Pro Tac Rail Mount 2 625 Lumen Professional Tactical Flashlight with High/Low/Strobe w/2x CR123A Batteries - 625 Lumens,Black https://www.amazon.com/dp/B01AXR8IKS/ref=cm_sw_r_cp_api_i_18vUEbYHFRQZ6
Assuming one of these, that's the best answer. This will outperform LiFePO4 16340s by a significant margin, especially if you use the unprotected Sanyo UR16650ZTA and a 4.35V charger. Of course, it's on you to avoid over-discharging the unprotected battery[.](/u/ReversE_3ngineeR)
Streamlight ProTac 2L. Just a hair over $100, but is a solid light. Comes with a normal push button and tail that can do strobe, low/high, or high. Only for a rifle or shotgun if you were asking about pistol lights.
If you don't get a bite, https://www.amazon.com/dp/B01AXR8IKS/ref=cm_sw_r_cp_apa_fab_AbRzFbBRMHE5J
In the first few questions/comments there's a post to tell how to spot a fake from Amazon. I bought one it was legit and no issues.
$105 and free shipping from Amazon (be aware you might get a fake).
Same price from B&H (not sure how legit it will be)
~~$110 shipped~~ ~~from Locked and Loaded~~ ~~(might save you some tax)~~ OOS
$105 on Amazon and not too shabby for the price!
https://www.amazon.com/Streamlight-88059-Professional-Flashlight-Batteries/dp/B01AXR8IKS
Amazon has those streamlights for $103 bnib.
https://www.amazon.com/Streamlight-88059-Professional-Flashlight-Batteries/dp/B01AXR8IKS
I have this light already https://www.amazon.com/gp/product/B01AXR8IKS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
I plan to put the pressure pad on the right side of the handguard, there is a place to put it there on the S-one right? A secondary goal for this rifle is to be "sorta lightweight" so I'd prefer to stick to the S-one unless it will fuck my plans for light placement
And I have 3 PMAGs my buddy bought me as a gunowner congratulations present so I'm ok there.
Been happy with my streamlight. 105$ on Amazon. Mounts on a rail. Comes with remote pressure switch.
https://www.amazon.com/dp/B01AXR8IKS/ref=cm_sw_r_cp_apa_i_fWtuFbHABMGAV
This: Streamlight 88059 ProTac Railmount 2L Dedicated Fixed-Mount Long Gun Light, Black https://www.amazon.com/dp/B01AXR8IKS/ref=cm_sw_r_cp_api_eCIKAb4M9HKGP
I ordered this mount: https://www.magpul.com/products/m-lok-extended-cantilever-scout-mount
and this light
https://www.amazon.com/Streamlight-88059-Railmount-Dedicated-Fixed-Mount/dp/B01AXR8IKS
I think it will do well!
Probably the best bang for your buck quality rifle lights right now are:
https://www.amazon.com/Streamlight-88059-ProTac-Railmount-Black/dp/B01AXR8IKS
They come with pressure switches, mounting accessories, etc. That and they are compatible with Surefire Scout type mounts.