Can a high temperature grease (axle grease, automotive grease, bearing grease, etc.) be used as a substitute for the normal oils we use in our guns?  Or possibly a combination of grease and oil?  Are there any negatives to using it?  I am just wondering if it could cause any chemical damage or premature wear.  I put a little on the hammer/trigger contact point and I swear the pull is smoother.  I'm wondering if it could be used to put a super light coat on the Carrier to make the cycle smoother.  I noticed the 2 BCGs I have came with some sort of grease on the gas rings. It looked like Royal Purple, I know RP makes a gun oil but I don't know if they make a specific grease.

For the temperatures and stresses a firearm puts on grease you'll be fine.  Military Grease, Automotive and Armaments is growing into obsolescence for high-speed vehicle operations but is fine for small arms.

absolutely.  I use the red lithium stuff from walmart on a ruger mini and some pistol slides..  Its the ol' Garand rule: "If it rotates,oil. If it slides, grease.  I use to use it on my AR's, on the slides of the carrier, but i stopped using petrol based. I wouldnt use it on the bolt. Grease can really collect the carbon.
A  dab will do ya.

i tried grease on my LWRC and it didnt like it one bit. had many short stroking issues. this was on a shorty 12.5" though that was cut back from 16" and over gassed with a huge port size. it shot fine with normal oils though.

havent ever tried on in a DI rifle, maybe i will but mobile 1 has been working so well its hard to justify changing because cleaning out carboned up grease it a pain in the ass.

I lube my BCG per this guy's method, using the same grease.  Few hundred rounds through it without a single hiccup.  https://www.youtube.com/watch?v=rzVr7JXVxH4

I use a weapons specific grease (XF-7) in my ARs, but mostly Slip EWL.

Both of those are pretty expensive, around $12 for 2oz. I got 9oz of multi purpose grease for $6.

That's a pretty good video. Been lubricating my AR like that for a while now.

Yeah, he's posted a bunch of good videos, and he is a firearm instructor - from what I've dug up on him, a pretty good one too.  I've been cleaning my rifle more thoroughly after shooting, mostly because I can usually find the time to get real intimate with it, lol.

I use red aircraft grade grease on my Garand bold and op-rod tabs, and on my ARs bolt slides.
Oil and a mixture of oil and ATF on rotating or reciprocating parts. I still use CPL on the AR bolt itself because it repels carbon better in my experience.

Geissele sells some good trigger lube. I believe it is an aircraft grade grease of some type.

Has anyone heard about heating the BCG in Z-Max up to 150 degrees engine lubricant for it to soak into the metal and semi-permanently lube it?.

In my 10 years working on high performance engines, additives like Z-max don't do anything beyond the placebo effect.  Clever marketing and people's desire to spend less $$ and time maintaining and fixing the machines they own are the reason additives (among other useless automotive products) sell.  Funny thing is- most of the time the "peace of mind" people get after using said products ends up costing them more in the long run.  

I'd imagine at best the same results would be seen with a BCG.  However, the heavy wheel bearing grease does a great job not flinging around everywhere when the bolt cycles, and does a great job preserving it's lubricating ability as it get's dirty.  Because it doesn't fling around everywhere, I've noticed that after hundreds of rounds fired, my bolt is very easy to clean, and I have yet to experience any malfunction of any kind with my newest rifle.

When it comes to grease for firearms, I use only Militech 1. 1 oz. will last the average gun owner for years. You don't slather it on, but apply it in a thin coat over just the friction areas. I also found out it I like it as a general purpose grease, like for bicycle ball-bearings, etc., so I bought a grease gun tube of it.

i am new to ar's but i have used lithium grease from walmart on my stag that i sold and it worked fine i used it like this guy  https://www.youtube.com/watch?v=ed9oU8V7-Uk

Mobil 1 synthetic oil. I collected and combined the leftover from 4 qts from an old change many years ago.

I put that $#/+ on everything!