Red Dot Placement?

[djegators]

I have been accustomed to seeing red dots mounted more forward on the upper, but I recently came across this thought process, where the red dot is all the way rear, and the rear sight is placed in front of it. Thoughts?



https://www.youtube.com/watch?list=WL&index=55&v=YhPchsAD-O8&app=desktop

[Hmac]

I don't use irons...don't even mount them anymore unless I'm using the rifle for a course...so I do mount the RDS farther back and it works fine for me. I can't get it all the way back because I need enough room for the magnifier.

[Hammer27]

I've seen this video brought up on another forum. I'll just say this: if putting the optic nearest your eye was correct, don't you think you'd see more people doing it?

[TexasAggie2005]

I've seen this video brought up on another forum. I'll just say this: if putting the optic nearest your eye was correct, don't you think you'd see more people doing it?

Well, I agree I see a lot more knowledgeable folks running all the way forwards on the upper. But what makes it better from a technical standpoint?

[djegators]

I have been thinking about this, and talking with people I consider SMEs, and I think there is an issue with periphery vision, etc esp with both eyes open, but more of a problem with occur if you do use the iron sights, trying to see thru the diopter at that distance.

[Hmac]

I've seen this video brought up on another forum. I'll just say this: if putting the optic nearest your eye was correct, don't you think you'd see more people doing it?


Well, I agree I see a lot more knowledgeable folks running all the way forwards on the upper. But what makes it better from a technical standpoint?

I'm not saying that mounting the RDS farther back is better ... that's going to be a shooter preference thing. But it's pretty simple to just move the optic back and give it a try on your next plinking trip. Wouldn't it be reasonable to try it before discounting?




I have been thinking about this, and talking with people I consider SMEs, and I think there is an issue with periphery vision, etc esp with both eyes open, but more of a problem with occur if you do use the iron sights, trying to see thru the diopter at that distance.

Huh? I thought the guy was talking about RDS, not magnified optics.

[Wake27]

If nothing else, that shortens the sight radius of the irons which has proven effects (generally negative ones).


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[djegators]

Huh? I thought the guy was talking about RDS, not magnified optics.

I was referring to the eye relief for the diopter of the BUIS.

[Hmac]

I was referring to the eye relief for the diopter of the BUIS.

Ah. That's an excellent point and actually a pretty sophisticated concept that is fundamental to the function of a rear aperture sight. I don't think the guy in the video addressed that, only the fact that he felt that the decreased sight radius was no big deal.

[matthewdanger]

I have tried this to a smaller extent on a couple of carbines. I don't place the rear back up sight in front of the RDS but have tried placing the RDS as far back as a traditionally placed back up sight would allow. Aperture sights are really meant to be used with your eye closer to the rear sight so I haven't been willing to change the rear sight position.

You can completely discount the idea if you are going to use a night vision monocular or magnifier. Mounting the RDS forward on the receiver is the only way to leave room for those items. So, some common intended uses for a carbine just won't work with the RDS mounted to the rear.

If you don't intend to use either a NV monocular or magnifier, there may be some benefit - especially with tube style micro RDS. It seems to be easier to find the dot from awkward positions when the RDS is closer to your eye though easier is pretty relative considering it isn't that hard to begin with. Think of trying to look through a narrow tube like a drinking straw. It is easier to do at arms length or when it held directly in front of your eye? That is an extreme example but it is the principle at play here. I don't see it as a field of view issue but rather an issue of making it easier to align your eye behind the optic.

Regarding the idea that no one does it so it must not be good, I don't think that is the case. There is at least one industry pro placing their RDS this way. Off the top of my head, a recent Trijicon MRO video shows Steve Fisher's carbine with the RDS mounted further back than most: https://youtu.be/HSShOQYUqjE

[djegators]

Ah. That's an excellent point and actually a pretty sophisticated concept that is fundamental to the function of a rear aperture sight. I don't think the guy in the video addressed that, only the fact that he felt that the decreased sight radius was no big deal.

Well, he addressed by dismissing it, saying you will very rarely if ever use your sites....kind of a cop out now that I think of it.

[militarymoron]

I also had the same question about the use of the rear aperture. Placing the rear BUIS forward of the optic limits the use to the large aperture. The two examples of rifles with rear sights forward that was used in the video weren't rear aperture sights, so i felt the comparison was flawed. Placing the rear aperture sight more forward also makes it more difficult to use, for the same reason he's advocating placing the primary optic further back. With a parallex-free RDS, you don't have to center your eye perfectly in the tube - it's more forgiving. With iron sights, you have a smaller 'window' in which to line up your eye through the rear aperture with the front sight, so they're much less forgiving (when it comes to maintaining cheek/eye position) when shooting from different positions.

Also, placing the primary optic far out at the end of the handguard to illustrate a point is fine, but the more practical test would be to shoot it placed at the rear vs. whatever the current position is (usually at the front of the upper receiver); not out at the end.

I guess are that there are pros and cons to whichever method you pick, and you just have to weigh them for your personal needs.

[HKGuns]

Well, I agree I see a lot more knowledgeable folks running all the way forwards on the upper. But what makes it better from a technical standpoint?

It comes down to personal preference, as well as the age of your eyes...... However, banging it up against your eyeball pretty much limits your peripheral vision and thus occludes your situational awareness.

ETA: The type of optic and what you are doing with it certainly comes into play as well.

[Hammer27]

Regarding the idea that no one does it so it must not be good, I don't think that is the case. There is at least one industry pro placing their RDS this way. Off the top of my head, a recent Trijicon MRO video shows Steve Fisher's carbine with the RDS mounted further back than most: https://youtu.be/HSShOQYUqjE

He doesn't have it the same way as the OP's video. Fisher still has the irons behind the RDS and we'll note that he has a rather generous eye relief, not the super close set up that's being advocated as better.

Again, we have the benefit of the best funded and best trained military and shooting public using the M4 platform with various optics for the better part of 2 decades. If it was better someone with the credentials to back it up would have done it before and it would be a standard. But no one is. No one in uniform, no one in competition.

It ruins your peripheral vision, decreases eye relief too much, reduces the ability to use the irons. Let's also note that it likely makes it slightly harder to flip up the irons, messes with your protective mask and will probably knock your NODs if you bring the weapon up a bit too eagerly.

[matthewdanger]

He doesn't have it the same way as the OP's video. Fisher still has the irons behind the RDS and we'll note that he has a rather generous eye relief, not the super close set up that's being advocated as better.

Again, we have the benefit of the best funded and best trained military and shooting public using the M4 platform with various optics for the better part of 2 decades. If it was better someone with the credentials to back it up would have done it before and it would be a standard. But no one is. No one in uniform, no one in competition.

It ruins your peripheral vision, decreases eye relief too much, reduces the ability to use the irons. Let's also note that it likely makes it slightly harder to flip up the irons, messes with your protective mask and will probably knock your NODs if you bring the weapon up a bit too eagerly.

True, it is obviously not behind the sights in the video. It is further to the rear than what is typical and is leveraging the same concept though not to the same extreme which is was the point of my post. I absolutely agree that mounting it behind the sights makes the rear iron sight more difficult to use and probably isn't optimal. I am not even saying that mounting it further to the rear is optimal or even better - only that I have tried it and not seen many of the theoretical downsides that have been noted. I also didn't really see many upsides so the loss of magnifier real estate wasn't worth it to me.

I have tried Aimpoint Micros mounted the same way shown in the Steve Fisher video - further to the rear but still in front of the rear sight. There is no real detriment to peripheral vision if both eyes are open (or even when they are closed). The housing of the RDS basically blurs into a greyish shadow and doesn't really occlude anything just like it does when slightly further forward. I suspect it you would be absolutely right on an RDS with a larger housing. That could enough field of view that your support side eye may not fill in the gaps.

The military has other considerations that may prevent this mounting position as we both noted - night vision, magnifiers, etc. Regarding eye relief, that seems like a non-issue with RDS but I fully admit I may be missing something there.

I put both set ups on a timer and noted no real difference in time so that right there was enough for me to not pursue it further. The only benefit that I could quantify was that, with a micro tube style RDS, I absolutely could see the dot sooner in situations that the carbine is coming to the eye like when it is coming up from low ready. You can pick up the dot while the rifle is at a steeper angle when the sight is closer to your eye. This is easy enough to test. That was an aid in awkward positions but didn't really translate to anything on the timer when standing though I guess it might have been an improvement had I tried it with something like a VTAC barricade.