I am having what I believe to be excessive gas problems in my AR.  16" barrel rims getting ripped off of cartridges, FTE problems, etc...  I am wanting to try a factory load that is would be the least "hot".  

Any recommendations?  

would a lower bullet weight produce less pressure?  

I am thinking along the lines of the Winchester 40gr Varmit packs.

I don't know if it is excessive gas problem with your 16", but the Winchester 40 gr varmint won't solve it.  It is catalogued at 3600 fps so probably has the same amount of powerder as the 55 gr. In my search for light practice ammo, or close range "hose 'em" match stages, I found that no one really make factory load (or reloads for that matter) less than 3000 fps, so I ended up reloading myself.  23.0 gr of H335 and 55 gr bullets make a nice/soft shooting 223 (chrono at about 2800 fps).

Yeah, I'm not sure that going to lighter ammo will solve the problem. The problem would be your rifle itself, something's wrong there, that's for sure.

However, I have found the Ultramax round loaded with the Nosler 40gr ballistic tip to be the lightest load in the market. I have chrono'ed that load right at 3000 fps (20" barrel), which for a 40-gr load is real mild.

What kind of gun is it?Is it chrome lined?Is it clean?Maybe there is a ring in the chamber.Is it a .223 chamber or a 5.56 have you been shooting nato spec ammo out of a .223 chamber?Give these guys more info if you expect answers

I bought the upper used.  Unknown manufacturer.

It is more of a project to see if I can get it running reliably.  So I dont want to sink alot of money into it.  I have 2 other ARs that run flawlessly.

The gas tube looked well worn and I have replaced it.  It has not been shot since the replacement.

I have run some scotchbrite-on-a-dowel in the chamber with a drill to make sure it is smooth.  

Maybe the gas port in the barrel is too large?

If you’re looking for low pressure, a commercial softpoint or hollowpoint round is probably your best bet since it was designed for a .223 chamber.

Also, check ballistic tables of ammo manufacturers and look for rounds with a low velocity (staying with the same bullet weight, of course).

Incidentally, PMC ammo has always struck me as pretty mild.