Front BUIS Mounted on slightly wiggly Railed Handguard of SIG556?

[rugerglocker]

Took off my 1-4x scope and going with a Red Dot, so I need BUIS.

I'm pretty sure I know the answer I'm going to get, because I haven't seen or heard of anyone doing this. But anyway, is it reasonable to mount a front BUIS (AR-15 hardguard height) to a Sig 556 forearm rail top? The reason I ask is the rail has a decent amount of play in it (I can jiggle it with my hand slightly--maybe 1mm). I would not mount an optic on it, but I'm not that great with irons anyway, so would it make a noticeable difference? I'm guessing I get a few MOA worth of movement from the rail, can most people shoot under 5 inches @ a 100 w/ irons?

Samson and MI make sights that go in the rifle's gasblock dovetail, but the Pic. rail mounted sights are more easily and cheaply found, not to mention they can easily be moved to a different setup.

Thanks

 

[G27RR]

What model is your 556? My SWAT model has no play in the railed forearm and the included rotary diopter irons work quite well. Maybe your forearm is out of spec or not installed quite right?

I put a Nikon red dot on mine because it was perfectly cowitnessed out of the box. That way I can leave the irons in place while I use the dot, or turn the dot off and shoot the irons with the Nikon in place.

 

[rugerglocker]

My sig is an older ER ("M4") model from around 2008 before they started making the "classic." It has an "M4" (AR-15) style fixed adjustable stock. It did come with the old plastic "fishgill" guards and I later got the alum. rail. Pretty sure the rail/guard is on correctly. I'm not sure but I think the newer ones are secured differently? Mine is 2 halves (top & bottom) that fit together with tabs, and then the whole guard is secured by the bayonet lug and the front takedown pin, so there's a slight wiggle.

I see you have the shorter gas system, that looks nice.

 

[Tirod]

If a scope with no iron sights is acceptable - which it is for bolt gunners the last 30 years - then why is a red dot required to have BUIS?

If BUIS are that important, then why not have them permanently mounted, instead of clamped on with the reliability problems that brings?

Sure, there are shades of how far it needs to go, but the black and white is if the optic can't be trusted, there's a reason. ANY glass optic is subject to damage and failure, it's up to the user to determine how important it is to be able to use the rifle regardless.

Civilian plinker and shootin' berms, not so much. Hunting, nice to have, but not absolutely mandatory. If far from home, being able to keep hunting is nice. Another optic can be used, too, which is a common bolt gun answer when on a trip.

At $100 to $250 and up for BUIS, another inexpensive backup red dot would do better - it's a red dot.

Point being, if iron sights are absolutely essential as insurance something is on the gun to use, then iron sights are the answer. The best iron sights are hardmounted and part of the gun, not clamp on accessories. If the gun doesn't need them because of an optic, then don't bother - have another optic for backup. It's the primary sighting system being used.

Non-duty sporter carbines don't need BUIS; mounting them should be a solid as possible, or they are essentially useless.

 

[briansmithwins]

Thousandths of a inch of movement on the rifle are going to translate to MOA movement downrange.

Figure out a different mounting system for your BUIS.

As for wither or not you need BUIS, ask yourself this: Will people die if I can't use my rifle effectively? If the answer is yes than you need BUIS.

BSW

 

[G27RR]

My sig is an older ER ("M4") model from around 2008 before they started making the "classic." It has an "M4" (AR-15) style fixed adjustable stock. It did come with the old plastic "fishgill" guards and I later got the alum. rail. Pretty sure the rail/guard is on correctly. I'm not sure but I think the newer ones are secured differently? Mine is 2 halves (top & bottom) that fit together with tabs, and then the whole guard is secured by the bayonet lug and the front takedown pin, so there's a slight wiggle.

I see you have the shorter gas system, that looks nice.

That makes more sense to me now. I wasn't aware of that model. I got mine in 2009 at some point. I agree with the others that the slight wiggle will cause problems, and a good red dot should be sufficient by istself for anything but duty use. Maybe carry a spare battery rather than having BUIS, or go with the gas block mount. I think you'd be frustrated with a front sight on a moving pic rail.

 

[rugerglocker]

OK thanks for the input guys, had a feeling the answers would be similar to this. I for sure want BUIS because the red dot will eventually run out of batteries, and with my luck I won't have a spare battery when it does. Also if the gun were to be used in a survival situation, you would obviously want to have BUIS.

Thanks again.