Hole spacing of Aridus Remington CROM

Howdy, folks. I would appreciate it if someone who owns one of these mounts would measure and let me know the hole spacing.

I need to put an optic on my VCS 870 that I bought from Hans back in '97. The ghost ring was great back then, but not so much for my eyes now. Even so, I like the Aridus just to have the GR as backup.

The hole spacing on the current MMC rear sight base is about 1 13/16 (1.812). I am hoping that the Aridus holes either side of the GR match this, so that I need only one new hole to be drilled and tapped. I'd rather not buy the mount and then find out the holes do not match.

I did search the forum and the Web for the spacing, without success. Aridus has no specs that I could find on their site. My searching might be weak; I also could not find the Remington OEM spacing, which surely must be somewhere online.

thanks, bws

Paging @SpyderMan2k4 to the white courtesy phone please.

If he doesn’t answer, I’ll try to remember to get mine and measure the spacing. IIRC though the spacing is based off the “new Remington” receivers which is different from the original Remington receivers. I don’t believe the spacing matches my early-00s 870 but I’m not 100 percent sure right now.

Offered on the off chance that the info might be useful to someone else who has an 870 without factory holes and is curious about mount placement.

I purchased both an Aridus Remington/RMR CROM and a GG&G 3035 Remington RMR mount. Kudos to Scalarworks for providing a drill/tap engineering drawing online.

I measured with vintage Goodell-Pratt calipers, matched against a steel rule 32nds scale and converted to decimal. LOL. I understand there is ample opportunity for error in measuring (especially with my crooked eyes) and converting the values, but it's what I have. I know the decimal places are silly, no need to tell me. No one is going to use these values to drill.

Rear means closer to the butt; front means closer to the muzzle.

MMC OEM rear GR mount hole spacing:
front and rear is approx 1.8125"

Aridus Remington/RMR CROM hole spacing:
rear and middle is approx 1 13/32 or 1.40625 "
middle and front is approx 2 28/32 or 2.875"
rear and front is approx 4 9/32 or 4.28125"


GG&G 3035 Remington RMR mount hole spacing:
rear and front is approx 1 15/32 or 1.46875"

Scalarworks Sync4 Remington/RMR mount specified hole spacing:
rear and front is 4.28"


I know people will use the actual mount as their guide for drilling, but I am used to being able find specs for just about everything where specs might matter or be useful. I'd buy the Scalarworks just because they put the drill/tap guide with spacing numbers online; not everyone's 870 has factory holes. However, I want to have the GR and their mount doesn't have one and leaves little room to put one in separately (a Trak-Lock might work, as they install back on the curved area of the receiver).

I thought I might find the Aridus (OEM Remington) spacing in the patent for the CROM, but I could not find a patent online. Maybe it's pending and private. The Scalarworks mount patent is interesting. The Aridus Q-DC mount patent is really interesting; so much thought and effort went into getting that product right. BTW, Aridus shipped my CROM almost instantly after the order went through and I got it in 2 days. Kudos!

bws