I have a relative that passed away and they had  couple of ammo cans of 9mm ammo.  All the ammo was loose in the can (not boxed or bagged).  The sticker on the can says 115 grain 9mm factory loaded but when I look at the casing bottom some is marked +P and some is not.  I want to be sure what I am looking at is safe to use.  I have several pistols ( all purchased new within the last 5 years ) and one 9mm rifle (CX4).  Would you feel comfortable with it or should I take it to my local gun shop and let them look at it.  I looked at the manuals for my guns and the CX4 says +p is ok but should not be overused.  The pistols (sig p938, springfield xde and ruger sr9c) do not mention +p ammo.  Thanks

Separate the +P it’s definitely hotter than normal stuff. The guns manual will tell you yes or no. Some defense ammo is +P. It’s not something to shoot a lot of out of most pistols. It can beat them up, increase wear, etc. usually the Rugers will be ok, just not a steady diet of it

Some is marked +p and some has a mark which is a circle with a cross in it.  It sounds like this may be a NATO round which is similar to +p.  Does that sound right and if so should I just go thru it all and separate it out to be on the safe side?

Are the +P marked cases loaded with hollowpoints or FMJ? Typically +P rounds are HPs. If what you have all have the same projectiles, you might have reloads using mixed headstamp brass.

It seems odd that someone would dump +P and not +P ammo loose into the same can...

I have a can of hollow points and a can of FMJ.  Both cans have headstamps that are very different, some say +p, some regular 9mm, some have the cross inside a circle.  My first thought was the same as yours, that they were reloads with used cases.  I know absolutely nothing about reloads.  All of the projectiles match, that is, all the hollow points look the same and all the FMJ look the same.  The stickers on the ammo cans does not indicate +p or not.  For example , the FMJ says "9mm 115 Grain FmJ metal case, Factory loaded.  I want to believe that they are all "regular" 9mm.  My brother in law that owned them was a vet and knew a lot about guns.  I dont think he would have mixed them all together.

This is a great example of why one should not just dump ammo willy nilly into ammo cans. Who the hell can know what that ammo was. Ammo cans can have all sorts of old stickers on it so dont assume that's what's inside.  

The +P will typically be 50-100 FPS faster than regular ammo, assuming same bullet weight. You will be hard pressed to tell the difference in recoil but I would still separate them from the non +P. It's also possible that someone reloaded ammo using whatever brass they had. The + in a circle means NATO standard

If all the ammo looks identical, same head stamp especially if hollow point and/or the primers have sealant, then it's most likely factory ammo.

In terms of safety, its worth noting that almost no "+P" ammo is loaded to full +P pressure of 38,500psi; the vast majority is loaded to NATO pressure of ~36kpsi.

Case in point, Federals 9BPLE "+p+" is actually just a full pressure 38.5kpsi +P.

The point being, there is no real concern firing any manufacturers "+p" ammo; modern guns are plenty strong, while modern ammo is actually fairly weak.

Standard WWII era 9X19 regular pressure was 116gr @ 1250fps from a 4.5" barrel, as a point of reference to modern ammo.  

It’s probably bulk reloads.

This.

All the same projectiles but different head stamps strongly suggests reloads.

The previous owner might have meant reloads from a company vs. an individual's reloads, or may not have made the distinction between factory fresh and commercial reloads...

Update.  I was able to track down the company that did the reloading.  They specialize in this and assured me the rounds were safe to use.  I spoke to them and visited their website.  Thanks for all the help.

This is the answer