FPC 9mm back-up iron sight question

[BadTeethNoBar]

Howdy,

The FPC has just a top picatinny rail, and after market sights are required. I've installed a 25mm red dot sight on it, and zeroed it over several range visits to a 20-1/2 to 85 yard zero.

I think red dots are probably reliable enough these days that the majority of pistol caliber carbine shooters are OK with just the red dot sight or optic by itself. I tend to over-think things, and so I wanted to have back up iron sights too. So I've installed a set of Magpul MBUS 3 flip-up sights at the longest possible sight relief. They stay folded down and reasonably unobtrusive until I need them, which is hopefully never. But now I've got to go ahead and zero the aperture windage and front post elevation.

Is there a quick and dirty method for getting this in the "ball park" using the red dot sight? I mean, as a sort of "co-witness" can I switch on the red dot, and then align the front post with it as a rough equivalent before the switching it off and zeroing things at short range on a target and the walk it up at progressively longer ranges? I've got plenty of ammo, it's just the time issue.

Thanks for any insights you might have on how to proceed.

 

[McChemist]

Howdy,

The FPC has just a top picatinny rail, and after market sights are required. I've installed a 25mm red dot sight on it, and zeroed it over several range visits to a 20-1/2 to 85 yard zero.

I think red dots are probably reliable enough these days that the majority of pistol caliber carbine shooters are OK with just the red dot sight or optic by itself. I tend to over-think things, and so I wanted to have back up iron sights too. So I've installed a set of Magpul MBUS 3 flip-up sights at the longest possible sight relief. They stay folded down and reasonably unobtrusive until I need them, which is hopefully never. But now I've got to go ahead and zero the aperture windage and front post elevation.

Is there a quick and dirty method for getting this in the "ball park" using the red dot sight? I mean, as a sort of "co-witness" can I switch on the red dot, and then align the front post with it as a rough equivalent before the switching it off and zeroing things at short range on a target and the walk it up at progressively longer ranges? I've got plenty of ammo, it's just the time issue.

Thanks for any insights you might have on how to proceed.

I zeroed my ARs and FPC using a laser bore sight (the long tailed version that inserts through the muzzle) projecting from my deck across the backyard to a wood fence. Then match up the two laser points. This is a preliminary rough zero at 51 ft. It is surprisingly accurate for what it is. That zero can be refined at range. As one thread put it. For HD, a one chest MOA is sufficient.

 

[JRD]

An FPC is really easy to bore sight to get a rough alignment for irons or an optic. Just partially fold the barrel and place your handguard on sandbags with the barrel pointing at the target and the receiver pointing off to the side. Look through the bore and align it with your target. Then have a buddy hold the barrel still on the sandbags while you adjust the sights to point at the target. Make sure you are occasionally looking down the bore as you fiddle with the sights because your buddy will probably change pressure and shift the barrel at some point.
Or use one of the laser boresighters you put in the muzzle.