So I took I took my rifle to the range for the first time in a while. I zeroed a new red dot for my rifle. I would like to loctite the sight down, but I don’t know when I will get the chance to zero it again. Should I just leave it mounted as is, or if I put it back on like it is with loctite.
OR do I really need to use loctite to keep it mounted securely.
If you have a quality Red Dot and mounting rail it should retain zero or very close to zero.
Your screws for the mounting rail should have Lock Tight.
So no, I wouldn’t lock the Dot down but check the screws on the Dot once in a while as you shoot it more. 
This is what I was looking for . I’m assuming if I remove the rail mount and then put it back on in the same place, I should be really close to zero right?
Should be. 
Just be sure you use the right Loctite as one is supposed to be basically forever and the other just locks in place and can be loosened if needed. Just please don’t ask how I found this gem out.
There should be a couple of threads exposed that the nut would have to screw over to come out, you could put a drop on them rather than removing and reinstalling. Orient the firearm so the Loctite wicks down to the nut.
I love this stuff, but I hate that it comes in a red container even though it’s loctite blue.
Maybe I’m not understanding the question. Why would you zero your rifle, remove the sight and try and zero again? Once zeroed, you should be good no matter when you shoot again.
My rifle is set up at a 50 yard zero with an EOTECH 512 w/3x magnifier, I’ve zeroed my rifle and sights maybe three times in 10 years. Once due to weather, once due to distance and once after changing ammo. Even after removing sights for cleaning and maintenance and placed in the same location, locked down, zero holds true. Slight adjustments for full value wind, but otherwise cold bore shots always within 1/8 - 1/4” Rock River Arms LAR-15 now w/30,000 rounds and still within 1/4” not a big fan of loctite on sights
Not every one can afford the good stuff. I am the same way, if I drop it or move it I always recheck zero. That way I have one less excuse for a miss. LOL.
So the reason I asked is I have a functional rifle right now. I can grab it and be confident with it. It’s a good quality sight (Sig Romeo 5). I wasn’t sure if I took the site off the rail and put it back on if it would be 100%. I know it should be, but I know any degree of change could make a difference.
I think I’ll leave it for now, and the next time I take it for a run I’ll loctite it the day before. OR I’ll just do it one of these days. It’s not zeroed out as far as I’d like, so as long as it’s really close it won’t matter. It’s more about mentally being able to trust it 
Part of that might depend on how you originally installed it. I’m probably telling you something you already know, but just in case, when you fire the rifle the sight inertia is going to try to hold it in place. Of course the rifle is recoiling backwards and the sight will eventually end up forward in the Picatinny rail (if that is your mounting method). Therefore, the sight should be pressed towards the front of the rifle when installing. If that is what you did originally, you should be able to 100% replicate zero if you remove it and reinstall the same way.
@Scoutbob Yes, mental trust in your equipment is important. I have left a firearm home because I wasn’t 100% sure it would work.
Is this the base that comes with the Romeo5 or did you get an aftermarket one?
If its the standard one, you should be well within a margin of error where any differences are just as likely user induced. This is especially true if as @Gary_H said, you are consistent with how you mount (press it forward). Maybe its not exactly 100%, but its like 99.9999999999999% 
Once locked in there should be no wobble side to side, front to back, or up and down.
I think your plan of waiting until the next range trip before unmounting, loctiting (is that a word?), and remounting is solid. You are then just confirming zero, should only require a few rounds for peace of mind.
If it’s a 3rd party mount, then “it depends”. Some are really good about return-to-zero and others aren’t. Cheap QD mounts are notorious for losing zero. High-end QD mounts or non-QD mounts are usually pretty good about keeping zero.
How are you liking the Romeo5 so far?
