I'm putting together a fun/utility gun and wanted to use a Burris Fast Fire III sight. After looking at available mounting options I chose the Allchin mount because it was the cleanest looking and got the sight closer to the bore centerline than anything else.

The underside of this mount is machined to fit in the channel that the rear sight normally rides in. I couldn't get it to fit in the channel. I measured the protrusion on the sight base in several places along its length and came up with a width of .284" - .2845". I then measured the width of the channel, again at several points, and found it to be a consistent .280". I happen to have an EGW Picatinny rail, also machined to fit in the rear sight channel. It went in with no problem. I measured the protrusion on that and found it to be .279" - .2795".

I contacted John Allchin and he stated that all his sights measure .283" - .2835" and are supposed to be a "press-fit" - he suggested I use a rubber mallet. I don't think I want to do that. He further assured me that he has sold upward of a thousand of these mounts and has had no complaints on any of the pre-drilled guns (mine is a 25-13). I find it hard to believe that my gun is an anomaly - or that a difference of .003" will press fit.

Has anybody out there run into this? If anybody is in the process of replacing a rear sight on a pre-drilled gun, I'd love to know the width of your sight channel. Fortunately I have a friend with a CNC lathe/mill that will thin this mount out for me, so that it fits like the EGW rail.

Thanks for any input.

Adios,

Pizza Bob

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NRA Benefactor Member

Allchin mount fit perfectly for me on a pre-drilled 686.

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-jwk-
US Army '72-'95

I mounted one on a 617 yesterday and it fit fine also.