I see several used Matech sights on Gunbroker for around $30 a pop.

Pics indicate a goodly amount of external wear.
Are these things trashed mechanically, or is the only main issue cosmetic?

Are you talking about some like these?
http://www.gunbroker.com/Auction/ViewItem.asp?Item=139664743

They do look well used, but I'm only aware of one inherent problem with the design, and that is that it's easy to over torque the mounting screw and put a crack in the mount. A year or two back there was someone here on the ee who was selling a beefier replacement piece. You might be able to do a search and find it (maybe in the archives). Or someone might pop in here and be able to tell you who it was that was selling them.

If you keep it as is though, just use a little locktite on the screw instead of really cranking down on it and it should be fine.



Edited to add: These don't lock in the up position, so I suppose if the spring was _really_ worn out it could allow some forward/backward play in the sight.

Thanks.

I was given a free one and I don't want to use that, it's on a rifle I rarely shoot.

It works well enough, on top of the weak mounting bracket and screw, it's bulky.  On a rifle with a 4x32 ACOG, that means having to mount the ACOG further forward than if the BUIS was lower and took up less rail space.  On a rifle with variable magnification optics, the height of the MaTech might not clear the ocular lens.   The detent that holds the sight stalk down can be worn, causing the sight stalk to pop up when it should be held down while shooting.

I got one back when it was kind of rare in 2003 or 2004, didn't read the manual and duly over torqued it

The hole is too small, the mount is too large, the gripper breaks if too tight....all when new.  Why the hell would you want a used one?  With a used one add to those other 3 vices the fact that the sight will not stay down when worn in some.

I have one I fond on a range minus the mounting bracket, if anyone knows who was selling replacements let me know.

It was Mongo001 who was making them. That said, I don't know if he still is but here is his user info page....





http://www.ar15.com/member/member.html?id=35058
ETA:








They beefed up that mounting bracket two years ago. Do you think there could possibly be any  on the market by now?



 
 

I would snag one for $30 bucks..

and since I READ directions, I tighten the screw until it stops and then add 1/4 turn more....
as for the aperature... I drilled it out to a larger size

and if the detent gets worn, I can displace a little metal on the frame with a punch and it's as good as new....

There not the best nor are they the worst... know there limitations and adjust accordingly....like most gear....