Is there a such thing as mounting an optic too far forward?

[PILMAN]

Hello, I seem to be getting a lot of negative feedback on a particular forum (not here) in regards to where I mounted my optic.

I purchased an older style quad rail (seems like it bolts to the barrel nut) and put my optic more forward to allow room for a mepro 3x magnifier since the meprolight m21 is a bit beefy. Clearly with it at the edge of the receiver rail, theres no room for buis or a magnifier. I was advised my method is unstable and nothing like an optic should be mounted there. The same individuals kept referring to my rail setup as freefloated which it is not, its a two peice dropin rail. Any thoughts? Comparison pictures.

 

[troy fairweather]

Bad idea to mount it off the receiver

 

[PILMAN]

Bad idea to mount it off the receiver

Why do I see many builds that have a magnifier mounted to the receiver and the optic mounted on the rail system?

 

[troy fairweather]

Why do I see many builds that have a magnifier mounted to the receiver and the optic mounted on the rail system?

Just because others do it doesn't mean you should.

 

[shoobe01]

Optically: do what you like. I know a (former AFSOC door kicker) who still keeps his RX01s way, way forward because he came up that way, is used to it, and shoots it well. Early red dots were often well forward; the Elbit Falcon was mostly mounted to a custom thing that bridged between the delta ring and the FSB in IDF service. The theory was something around getting the optic out of the way and not forcing your eyes to focus so close, but it's likely based on the use of pistol optics on barrel mounts for slug guns, and on things like the (Cooper) Scout Rifle concept, which generally pre-date the RDS.

I think /some/ of the trend to move optics back is that we've figured out the same concerns or benefits that magnified optics had are not conferred to RDSs, and that more truly 1x low-ends make the forward mounted magnified optic and bindon-concept snapshot use unnecessary.

But also: Mechanically, a lot of rail systems are not that secure so can wobble, vibrate, and even rotate or otherwise come loose. Non-freefloat systems can also have other distortion as things heat up or you apply pressure. It is safest to keep zeroed systems on the receiver. If your gun is rock solid and you are SURE of this, drive on. Put it where you like. But should not be necessary. Try it several places and see how you shoot with it.

 

[PILMAN]

Optically: do what you like. I know a (former AFSOC door kicker) who still keeps his RX01s way, way forward because he came up that way, is used to it, and shoots it well. Early red dots were often well forward; the Elbit Falcon was mostly mounted to a custom thing that bridged between the delta ring and the FSB in IDF service. The theory was something around getting the optic out of the way and not forcing your eyes to focus so close, but it's likely based on the use of pistol optics on barrel mounts for slug guns, and on things like the (Cooper) Scout Rifle concept, which generally pre-date the RDS.

I think /some/ of the trend to move optics back is that we've figured out the same concerns or benefits that magnified optics had are not conferred to RDSs, and that more truly 1x low-ends make the forward mounted magnified optic and bindon-concept snapshot use unnecessary.

But also: Mechanically, a lot of rail systems are not that secure so can wobble, vibrate, and even rotate or otherwise come loose. Non-freefloat systems can also have other distortion as things heat up or you apply pressure. It is safest to keep zeroed systems on the receiver. If your gun is rock solid and you are SURE of this, drive on. Put it where you like. But should not be necessary. Try it several places and see how you shoot with it.

quality reply thanks and great explanation. I grew up mainly on eastern block stuff so AKMs, the VZ58 and the Israeli Galil. While optics were there, during the early pre 2010 days, it was a pita to get optics so I never got into it until recently when I bought my first AR. I did see the Israelis use the mepro m21 sometimes on a carry handle but sitting jetted forward so I figured there was a reason the Israelis were doing it. Your explanation makes sense.

Do you think getting a 3x magnifier is a waste of time?

 

[Lo-Profile]

I keep mine further back on the upper receiver. I only use Red Dots on my AR pistol guns. I don't add a magnifier, so it works for me.
On my 16" and longer I use scopes so their magnified 4-12x44.
I also don't use BUS on any of them.

 

[trackskippy]

If the rail is solid and secure, I dont see a problem with it. The red dots on my AK's were on Ultimak rails in basically the same place as yours is on your AR, and I always preferred them there. They are out of the way there, of both handling and your peripheral vision, and contrary to what you often hear, dont mess with the guns balance. I really dont see any negatives mounting them there.

I think the only issue with the AR's would be if the rail wasnt solid/secure, which if it wasnt, wouldnt be a good thing anyway.

Most of my AR's dont have forward rails and I mount the red dots as far forward on the uppers rail as I can and use a cantilever mount, just trying to get the sight even more forward.

 

[Varminterror]

Take a step back and breathe - this decision won’t be made by convincing yourself a handguard mounted optic is an optimal choice, or is equivalent in performance to a receiver mounted optic - because it’s not. Plain and simple.

But, I don’t think validation seeking for this makes much sense. If you want it there, fine. But the mechanics of what you’re doing and the consequences thereof are well known, thoroughly proven. We mount optics to the receiver because the receiver has less opportunity to move and shift our relationship between POA and POI. We know mounting optics on rails, especially clamshell rails, can, will, and does elicit shift between POA and POI.

I would also challenge that it looks like you have room for a BUIS behind that optic when receiver mounted.

You’re shooting a clamshell rail, which is a concession in performance. You’re shooting a red dot, which is a concession in performance. Maybe you’re shooting lesser cost ammo which forces a concession in performance... how much performance sacrifice can you make and still satisfy your needs?

So that’s really it. If you’re willing to tolerate the consequence of a sub-optimal design which yields sub-optimal performance, then fine. Folks make such concessions every day in many ways which are much more important than optic position on an AR. If you’re choosing that optic and want BUIS (overrated and unnecessary) or want a magnifier, then you have what you have, and have to tolerate the consequences.

 

[jmorris]

how much performance sacrifice can you make and still satisfy your needs?

From the photos, he obviously has the ability to test both, on target and see if he can tell any difference himself with the combination he is using.

There is no reason to do everything exactly like everyone else but you also don’t want to jump from bridges just because others do.

Find what you like and don’t seek or expect approval from people that don’t even know you.

 

[jmorris]

I have a couple AR’s that I often swap optics around on for different situations. I keep a small pistol laser on them zeroed, swap optic and line it up with the laser is a very quick way to get very close without firing a shot.



However, look through a magnified optic while projecting the laser down range, then using different resting positions/sling tension and you can actually see the relationship change.

If you wanted to go one step further and see why free floated tubes came into existence in the first place, you could add another laser directly to the barrel. I made a V block and rudimentary windage/elevation adjustments for that laser level before I started using the cheap pistol lasers. At that point you can see what location stays closest in relationship with the barrel, receiver or hand guard.



If you can’t see any difference it might be a non issue for you. It might be there but lack the resolution to even see it.

Your reddot might be large enough to encompass the error.



That could be realized with a different optic.



If that is the case you are not going to see dramatic changes regardless of where you mount it.

 

[Skylerbone]

I started with a receiver mounted scope on my first AR then transitioned to an RDS mounted to a free float rail. That quickly returned to receiver mount. When that barrel heats up and that vented rail does nothing to stop it...and when accuracy is spotty.

Yes you gain some peripheral vision but not worth the compromise. I’ve never cared for the Scout Rifle concept.

 

[trackskippy]

I never had any accuracy issues with my AK's, and the Ultimaks were strapped/mounted right to the barrel. And they were often shot to the point you couldnt touch the barrel with your bare hand due to the heat.

I also had a Springfield SOCOM that had a scout mount on the barrel, and while it was steel, and got very hot, I never saw a shift in POA/POI with it, scope or red dot. Then again, it too was mounted directly to the barrel. Because it was made of steel, and got very hot and retained the heat, I was never really comfortable with the optics on it. The Ultimaks are aluminum and shed heat quickly, and never really get hot.

If you want the optic forward, and dont want to put the optic on the handguards rail, I have seen rails that attach to the uppers rail, and project out over the handguard, with no contact with it. Seems that would solve any issues you might be worried about.

 

[shoobe01]

To magnifiers:

Great, and I love them but... only if you are going to shoot far enough away, or need to find and identify targets further out. I have several guns with RDS+magnifier, because LPVOs* do not work so well with my eyes (have two though). I also have a couple without magnifier because it doesn't go out far enough, like my 9 mm.

When walking around the woods seeking game or badguys, the magnifier is flipped away. If something pops up close, it is dangerous and emergent so you can snap up and shoot through RDS. Further away targets or possibles are almost inherently less urgent and you can much more often perform other actions, so have time to find cover or concealment.

That said, RDS position is usually JUST in front of the magnifier. I... sorta have a vague recollection it doesn't work well to put the RDS too far away. Maybe shadowing etc; you can see the sight, not just through it.


Most magnifiers flip to side, but as a part of making RDSs ride higher having to do with passive night vision use (but some like it anyway) there are setups exemplified by the Unity FAST mounts, and things like their "flip to center" magnifier mount which goes /down/ instead of to the side. Neat stuff, but tends to work only with a few sights/magnifiers.



Normal cowitness (to irons) or higher will generally allow a normal flip-to-side magnifier to clear the rear BUIS. So you can do all the sight options together if you want. But also: RDSs are getting crazy reliable, plenty are starting to roll with no backups, and I don't know the last time I deployed mine so I am getting close to that myself.


* Low Power Variable Optics, scopes that bottom out at 1x, and have a daylight-bright red dot or other reticle illumination.