I am new to the AR platform, and just purchased my first one: BCM AR15 M4 Carbine 16". If has the standard F marked front sight, and I purchased a Magpul MBUS rear flip up sight. Gun will be used strictly as a home SD weapon. I have been reading many articles and watching many videos on zeroing the sights. I think I have a good feel for getting the rifle zeroed properly using the irons. Will probably use the 50 yard zero method. At some point, I would like to add a red dot. Can’t spend the money on a high-end Aimpoint/EOTech, so I’ve been looking at the Bushnell TRS-25. My question(s) are:
Do I need to add a riser mount to the red dot sight with my setup? If so, how do I determine the height I need?
Not quite sure of all the different co-witnessing/absolute co-witnessing explanations I’ve been reading. Do I position the red dot on top of the front sight when zeroing and just flip down the rear sight? Do I use the irons at all, or just the red dot? Should the irons be zeroed separate of the red dot?
Sorry if these questions have been repeated at some point before in this forum, but I appreciate any help/suggestions from the knowledgeable forum members out there to get me started in the right direction.
If you wish to use this sight to cowitness where the red dot matches with the point on the front sight you will need to mount the sight on a a medium height riser.
Since you are new to AR’s, I recommend spending your money on ammo and getting some trigger time long before considering a second-rate red dot sight. A good red dot sight, like an Aimpoint, unreservedly makes you and your weapon more effective. I wouldn’t bet my life on a cheap sight, though.
Do you have a white light on your rifle? If not, that should be your next purchase.
If money is tight the flashlight is the top priority after magazines and ammo, and maybe a sling.
Even after four years, my carbine is noticeably boring, with only a flashlight mounted to the FSB, Aimpoint T1 in an American Defense mount, and skinny CAR handguards to distinguish it. No railed forearms were necessary for me.
I have to agree, save up for an Aimpoint or Eotech. Aimpoint PRO probably best bang for buck. Next, probably Eotech XPS line.
Irons should be zero’ed separately from the RDS, but most likely the dot will sit on the tip of the front sight post when sighting through the RDS with rear MBUS flipped up. It’s an excellent place to start when zeroing it. The RDS is a completely separate sighting system. Ignore the irons when using it.
I have one that I replaced with an eotech. The dot was ok, not as crisp as an aimpoint or eotech and after about 200 rnds it would shut of with recoil and turn back on with the trigger reset! For a range gun, plinker or something like a .22 it’s ok, but not on a SD weapon.
But to answer your riser question, yes you need one. I purchased the trs that comes with the lower 1/3rd riser. If you search on amazon you can find the site and the risers for co-witness or 1/3rd.
Thanks for all the suggestions and feedback so far. Sounds like I should work on getting familiar with the basics like shooting and zeroing with the irons first. Then work on saving up for a quality RDS. I plan on zeroing at 50 yards/meters. Seems like that’s the favored distance to cover most distances with least amount of POA/POI difference.
OP said he intends to keep the rifle set up for SD (I’m assuming home defense/self defense?). Within the house, I would agree that the light is far more practical. Identifying targets before pulling the trigger is a safe and responsible concept, and any engagement at that range (15ft is a pretty long hallway for most houses) is not going to need an aimpoint. The aimpoint would help…but if money is tight, the flashlight is an essential.
OP, I agree that ammo and training is going to help you a lot. Find some local NRA classes and go in with an open mind, there’s more than one way to skin a cat. Add different techniques to your toolbox of knowledge. You also probably don’t need a $500 class as your first one, just so you can list it on your sig line. You’ll be able to afford the optic and training by learning the basics first, and saving up as you go.
For home defense, a light is important, but an RDS with both eyes open (as they are properly used ) provides a sighting system that is superior to irons for down-the-hallway shooting. I also agree that training is important, but I don’t think I’ve ever taken a carbine course where an RDS wasn’t part of the recommended or required equipment.
Buy ammo, then buy more ammo, then buy more ammo, shoot the hell out of it, repeat. Add accessories down the road after you learn and are comfortable with your new AR, time will tell you what you need next. just my $.015
Try out optics before purchase if you can. If your friends have AR’s with various types of optics on them, see if they will let you shoot a few rounds through each to help you decide.
I didn’t and it cost me a lot of money in mistakes. I ordered one of the mini-ACOG’s and ended up selling it before firing a single round with it. The eye relief was just too short for me. Similarly, I took to the Aimpoints right away and haven’t regretted a single one. I got to shoot someone’s AR with a Leupold 1-4 variable on it and didn’t care for that optic either.
Similarly, see if you can shoot a rifle with and without a co-witnessed rear sight. I waffled back and forth between the two and now I prefer the uncluttered view with a folding BUIS. You may decide just the opposite.