MFI Sig 556 Diopter Sights

I had purchased two sets of Sig 556 Diopter sights for my 551A1 and a 556..  Initial impression was that they were of good construction and the quality of fit and finish was quite high.  Installation was easy and strait forward.  The rear sight and rail was a snap while the front sight was typical Sig 556 and a third hand would have been useful.  Sig sights are of a good design, but replacing them requires some patience. 

This is the set I purchased:  MFI Website Page LINK

After some initial use, I discovered that the rear sight drum on on one of my sights was getting looser and looser.  I contacted MFI about the issue via their contact form on their website and received a very timely response from the owner of the company.  Not only did he offer to fix the problem, he looked up my invoice and advised that I likely had a similar problem with my other rear sight as both were shipped in a period when some Loctite omission issues were discovered and the manufacturing process was modified, eliminating the problem altogether.

I shipped them back on 1/11/15 and received them back, fully fixed and upgraded with the fiber optic inserts on 1/19/15.  Incredible turn-around in my opinion for a fix requiring full disassembly of the sights and return shipping.

As received back from MFI:

NOTE:  The damage and finish wear on these come from my initial use.  I shoot my rifles frequently and they are not safe queens. 

I was super impressed with the fiber optic inserts and was very pleased to have the owner of MFI offer to install them in both sights Gratis.  Thank you very much, classy move and very appreciated.

Naturally, I was anxious to reinstall them on my 551A1 rifle and a 556 Patrol rifle.

Here is the 551A1 with the MFI sights installed:

Sig 556 Patrol Installation:


Overall I am impressed with the sights.  They are a bit heavy compared to the Sig Rail and Diopter, but they do lower the sight axis which makes the rifle more comfortable to shoot.  Prior to the removal and return to MFI, The 551A1 was capable of good accuracy at 100 yards with the MFI sight and 200 yards it was combat acceptable landing strikes on a torso sized plate easily.  I have not fired these irons beyond 200 yards.  I typically run an optic (Aimpoint PRO) on this rifle, so the iron sights serve a back-up purpose for me.  I prefer the "fixed" nature of the sights in this back-up role as they are ready for immediate use as soon as the optic comes off the rifle.

The second set had not been sighted in yet prior to being sent in for repair, so no accuracy or opinions on the shorter sight radius patrol yet.  That is a project for Spring 2016.

I offer a solid thumbs-up on these MFI Diopter sights and can recommend them to a shooter wanting something that makes their 551/556 rifle look more like the classic Sit 550 / Stgw90 series of rifles that are in general issue today in Switzerland. 

I will have to sight in both of these rifles with the sights reinstalled, so I will be posting some targets for review as that task is accomplished.