View Full Version : Hahn Precision folding rear BUIS

6 June 2010, 12:38
I recently set out to find *my* perfect folding rear BUIS. I don't particularly care for many of the folding BUIS on the market because:

* Many are IMO overly complex for a BUIS
* Most have windage (and sometimes elevation) knobs that are too easy to inadvertently move
* Most are bulky
* Almost all have a clamp attachment that can cause canting

In my search I came across one that doesn't get much mention - the Hahn Precision rear BUIS: http://www.hahn-precision.com/armory/products/buis_rear.htm


The Hahn met all my preferences and needs. It's machined from a solid block of aluminum, has a simple steel aperture stalk, uses a standard A1 windage wheel and attaches to the rail differently than most BUIS.

The aperture does not lock up nor down. Instead, Hahn has used what looks like a standard A1 or A2 flat aperture spring to cam the stalk into position; it snaps into either position with authority. In addition, Hahn incorporated a steel crosspin as a stop for the stalk when it's elevated - no peening from this design.

The attachment method is different. The base is milled to slide onto an in-spec rail; after it is in position, two nylon-tipped setscrews clamp the sight into position. I had to oil the rail and gently tap the sight into position - mine was snug enough that even if the setscrews were both removed the sight wouldn't move much.

The sight is smooth without sharp protuberances to catch on gear. IMO it's as close to bombproof as you can get in a folding sight.

Sometimes it's good to look beyond the flavor of the week - you might just find a superior product!

More pics (sorry about the oil splotches and dog hairs - the finish is uniform):

6 June 2010, 12:46
Looks like the answer to a simple, robust BUIS.

Thanks for the review!

Optimus Prime
6 June 2010, 16:04
I like it... They look to have some other pretty cool items too.

6 June 2010, 19:44
Good review!

6 June 2010, 21:41
Nice work! I'm happy to see a review on this product finally!

6 June 2010, 23:53
Thanks for sharing the info. Many of my thoughts are similar on the BUIS and the need for simplicity. I like their use of the A1 style windage adjustment.

5 July 2010, 20:43
ive been looing for the perfect buis and thanks to you i think i just did!!!!!!

5 July 2010, 20:51
I'm still as impressed and enthusiastic today as I was when I wrote this - no warts have turned up.

22 July 2010, 14:04
Good review. Interesting product that merits some personal research.

Specialized Armament
1 October 2010, 18:28
We just picked up a couple and Mark put one on an MK18 that he dressed up a bit with a Magpul CTR buttstock, Aimpoint T-1 and some throwback single heat shield handguards. It is a well built unit and fit the Colt rail like a glove. The simplicity of A1 windage knob and flat spring operation is what attracted us to the unit.

http://i808.photobucket.com/albums/zz2/Specialized_Armament/MK18%20Limited/th_Raw154.jpg (http://s808.photobucket.com/albums/zz2/Specialized_Armament/MK18%20Limited/?action=view&current=Raw154.jpg)
http://i808.photobucket.com/albums/zz2/Specialized_Armament/MK18%20Limited/th_Raw153.jpg (http://s808.photobucket.com/albums/zz2/Specialized_Armament/MK18%20Limited/?action=view&current=Raw153.jpg)
http://i808.photobucket.com/albums/zz2/Specialized_Armament/MK18%20Limited/th_Raw152.jpg (http://s808.photobucket.com/albums/zz2/Specialized_Armament/MK18%20Limited/?action=view&current=Raw152.jpg)