Is there any reason to prefer 940 nm IR Illuminator over 850nm for hog hunting with digital night scope?  I was told 940nm will be less likely to be detected by hogs as 850nm will have more bleeding from lower nm light which hogs can/will see.  Is there any truth to this?  I was thinking 850nm would be better as it will give longer range over 940nm and will be cheaper to boot.

I've never had hogs spook from the faint red glow but have had deer see it and run, which made the hogs usually get jumpy but sometimes run.

Yes there is absolutely truth to this. Hogs are difficult to predict and one group may vary completely from another. Remember that probably still the most common method for hog hunting in the United States involves a red or green flashlight. When I had infrared light, both 850 and 940, I had some hogs they didn’t care and others that ran off immediately once I brought to light down.

You won’t know until you try. One important point is to be ready to shoot as soon as you get close to them with the light.

I'm beginning to have a few spook at the Game Camera's but that is probably closer than you will get before you open fire. Now I'm going to say a lot depends on how hard the hog's are pressured. I've killed some broad day light that just looked at me like they dared me to step across a line. Then I've had some that were so skittish that leafs blowing would set them off and then they'd come back and spook again. I often worry that the light reflection from the eye piece of my thermal will spook them but so far I've been lucky.

Me too.  I bought a 850nm IR bypass filter off ebay and cut it to fit over the 850 IR light source.  Problem solved.  It seems that it isn't the 850nm IR light, but the red lights just under.  The bypass filter blocked the red and let the IR through.  Stopped the deer from spooking the pigs for me.

Do you loose some range/penetration by putting the bypass filer in front?

I think all the illuminators I put the 850 bypass filters on were Streamlight products, which AFAIK are all rated at 850 output.  And, most of them have 30mm lenses that I replaced with the 30mm bypass filters.  WIth the SuperTac IR, I bought a 52mm filter and had to put the filter material into a Butler Creek scope cap since I couldn't get the damn lens out of the SuperTac.

But, to answer your question- no, not that I could tell.

Another upside is they're cheap.  30mm 850nm IR bypass for $10 delivered off eBay.  https://www.ebay.com/itm/30mm-850nm-IR-Filter-Infrared-Optical-Grade-IR85-Filter-for-Camera-Lens/182278640670?hash=item2a70a7541e:g:fHwAAMXQCgpRo4oR