Key measurements are well within spec:
Total width=0.8325, Recoil groove center to center=0.3935, Recoil groove width=0.2065, Recoil groove depth=0.1175

Interesting. I wonder if the rear will work with an Aurora front sight? I really like the Aurora's narrower sight post.



Mike @ MFI answered my email inquiry.(On a Saturday!) No, the Aurora front sight will not work with the MFI rear sight.



 

Bobro Mount for my Browe seemed a bit tight, but nothing crazy.

I put my Aurora rear sight on the MFI rail to check for any height difference

http://i58.tinypic.com/eajeg9.jpg
It looks like the MFI diopter sits just a little lower than the Aurora.

Now that is an interesting photo!  You can tell people at the range, that it is a backup diopter sight in case the primary diopter fails.

I'm very happy for MFI. I thought these would never get to market. I doubt I will sell my Auroras, but I wish MFI the best. This looks like a great product. I wish they'd been able to bring them to market back in 2009, but better late than never.

That is not surprising, as even the Swiss Arms' picatinny mounted rear diopter sight sits higher than the original welded on SG 550 series rear diopter sight. (Adding yet another sight hight to an already crowded field.)

One of the benefits to the MFI sight & rail, is that it uses the original Swiss mil-spec sight height making it compatible with front sights available from a number of sources including surplus, as well as from MFI without the hood, and soon from MFI with the hood.

The more I work with these MFI units, the more I like them. I tried mounting two commonly used models of ACOG scopes on the MFI sight and rail. Both a TA11 3.5 x 35 and a TA31 4 x 32 fit perfectly using standard TA51 mounts. There is sufficient clearance with either ACOG for them to be mounted far enough back for proper eye relief and a surprisingly good cheek weld. Plus, the MFI sight still works through the sight hole at the base of the ACOG, so that if the optic ever failed, you could rapidly transition to the MFI for backup without the need for quick disconnect mounts, or anything other than adjusting your head a bit.

TA31 4 x 32:


TA11 3.5 x 35:


The front sight is clearly visible through the base of ACOG. Nice!

Can anyone get me the measurement from the base of the dove tail to the top of the blade to be the proper height front sight for these? I thought I'd play around a bit while waiting for the fronts to become available.

The SIG 55X series are burdened with way too many different sight heights. Even ignoring all the other options, and simply staying with the original basic SG 550 spec that the MFI diopter sight and rail is made to line up with, the Swiss have no less than seven different front blade heights:



N+ is the standard height front sight, as well as the height MFI chose to use for their front sight. It's distance from the base of the dovetail (not the bottom) to the top of the fixed post is exactly 0.757874 inches. (As long as you accept the definition of exactly as being within a few hundred millionths of an inch.) While I double checked the height by measurement, the number comes from Swiss specifications (not in english).

Thanks man! Is the N+ the one on the left? It's a little dark in my picture.

 

Boar

My sight, which I removed myself from a demilled 551, does not have any markings.  It appears to be about the height of the one on the left in your photo, and pretty close to the height of the Aurora on the right in mine..  I hope the MFI rear is compatible!

Nope, N+ isn't in the picture. There are 7 different heights, and only three shown.
In the picture are: ( - )  ( N- )  ( + )
The whole set from lowest to highest are marked:
( -.)  ( - )  ( N- ) ( N )  ( N+ )  ( + )  ( +.)
The simple answer to your original question is three quarters of an inch:

My answer may have seemed a bit confusing, as I was having fun with the Swiss and their obsession with precision, as represented in having 7 post heights. It's not like the Germans aren't detail oriented, and H&K have one post height they use in all their diopter sights, which works quite well with everything from the G3 to the MP5. But some how the Swiss need seven for a single caliber.For some reason, not every sight gets marked. I think most unmarked sights are N+.

Thread return from the grave!

I got notice that my sight set is inbound, should be in my grubby mitts tomorrow.

I'll see if I can't get them installed and get some pics up over the weekend for those looking to see the MFI front sight.

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If any of you have the front / rear combo mounted on the Sig 556R, would you mind telling me if you could get a proper zero at 100m or 250m?
I understand that these sights are calibrated for the 223 round, and contact with MFI tells me that they do not have a rear drum for the 7.62 Russian.


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I got my MFI set installed this morning, plan to go test them out this afternoon at the range.

Pics as promised (in full potatoscope):









If it has not already been covered, the MFI front sight is anodized black and it is N+ height (which is almost too tall for my tastes, but it pairs with the rear sight well enough).

My initial impressions are that both the front and the rear are of pretty good quality. I'm still kind of bleh on the white infilled Swiss cross and the elevation markings are missing their important point marks, so on observation you have no idea which way your are moving the sight from the markings alone. The front flip down fiber optic post is comparatively HUGE... I may in the future buy a Swiss tritium flip post and replace it.

I'm also a little unimpressed with the fiber optics in general. As with any rifle rear sight the rear fiber optics completely blur and disappear in use... the point of illumination on a REAR rifle sight is to find it with your eye in very dark conditions... conditions that prevent fiber optics from working. So all in all the rear fiber optics are more gimmick than function in my opinion. The front fiber optic is more useful but as mentioned above the post it rides in is pretty big, and it changes the front sight from a "pumpkin on post" to a "direct point of impact" sort of sight. The front flip mechanism is tight and takes some effort to flip down and up, so there is little chance of it falling down under fire I'd imagine. The rear drum rotates very easily and smoothly... I'm used to HK diopters that take some convincing to turn and have these meaty solid clunks when they snap into place. This diopter feels soft and mushy by comparison... like the Aurora rear sight I had.

I'm off to the range to test it out this afternoon, so I'll have a follow on later tonight or tomorrow. I did do a rough zero with the sights using a bore laser in the basement and from what the laser says the sights adjust easily enough, have more than enough wiggle room for further adjustment and are hitting close to correct... but you never know until you are at the range.

I haven't even had a chance to haul mine to the range yet as I have the wrong front sight.

Well, my range report is kind of mixed.

Long story medium length, the sights hold zero but are a tad finicky to actually zero precisely, and there is a slight degree of POI shift between the apertures.

I set up to zero at 25 yards and using my basement jerry rig laser zero my initial grouping, using the first aperture (2) instead of the v-notch and my first grouping was low and left, but it was moderately tight. I did as the instructions recommended and adjusted the windage using bare fingers and adjusted the elevation with a small screwdriver. It took a few attempts to zero as the adjustments were kind of fucky, their adjustments did not seem to conform to a discernible MOA... but I was able to get a decent enough pattern where I wanted it eventually.

I expected the various apertures to employ some sort of BDC so when I switched to the "3" aperture I was expecting my POI to shift up... instead it shifted up a tiny bit but to the right slightly. I switched to the "3/4" aperture and it shifted slightly LEFT and up a little more. Thinking it might be user error I switched back to the "2" aperture and sure enough it was back to where I had zeroed it. So it appears the POI between apertures is a little wonky.

I also zeroed the sights with the flip up fiber optic in the up position, using it as a direct point of aim. When flipped down the smaller "pumpkin post" worked well enough, although the hits felt high. I think this is because the fiber optic flip sight sits pretty high above the fixed post on mine. "Pretty high" being a proper webster's dictionary definition for "I have no idea exactly how high".

I also tried out the V-notch open sight and found that it was more or less on point of aim, but the pattern opened up to about double what it was with the "2" aperture. Which is kind of expected... the V-notch is a very minute of man kind of sight IMO, enough to get the job done center mass but don't expect precision.

Anyway I stayed on the "2" aperture for the rest of the afternoon and the sights held zero for the rest of the day. I transitioned out to 100 yards (beyond the normal range I shoot my 553 clone at) and I was still on paper. Nowhere near accurate shooting as the pattern opened up pretty good, but I attribute that more to the short barrel than the sights, this 553 clone of mine is a 50 yard weapon max.

Anyhoo, in my unprofessional opinion these sights are decent enough to get the job done. They definitely are not precision instruments but they walk a fine line between copying the original design and cost effectiveness. With the "2" aperture zeroed I would trust my set for close range minute of grapefruit, but anything past 50 yards opens up... but half of that is the weapon, so the sights cannot be blamed entirely.

Just installed mine:

Bump before archived.

Got the second to last one MFI had.  Mine is perfect in every way.  Outstanding quality !
The owner was very responsive to questions.

One a scale of 1-10 in value, this thing is an 11.

Weird. I was showing a guy my 556 Classic today that has the MFI sights on it. He mentioned that MFI had stopped making them. I guess that's correct?

I do know that at least 1 set was still available at MFI when I purchased mine a few weeks ago.

How have you manage to avoid brass marks near the ejection port? Does that gun ever see range time? It sure is pretty.

Oh they are there, I just blacken them every once and a while to cut down on the clutter.



And dayam is this thread old.

I guess as a follow up my MFI sights are still installed and still working for the most part. I rarely shoot this rifle because it is unsuppressed, and this short barrel is no fun at my local range which has too many walls.