Ammo experts:

Just wondering if anyone else has noticed that for ammo with the same specs (weight, velocity, ...), sometimes a company will call it +P while others do not.

Example:
CCI Blazer .38 Special, 158 gr, TMJ, 850 FPS, 253 lbs energy = +P
S&B .38 Special, 158 gr, FMJ, 890 FPS, 278 lbs energy = not +P

What gives? Official SAAMI standard states 158 gr @ 900 FPS yeilds average of 17K PSI standard. (vs. +P @ 1050 FPS yeilding average of 20K PSI). How can 1 be +P with lighter specs and the other not +P?

S&B's website specifically states it is not +P nor is it printed on the box.

Reason I ask is that some of us are shooting older pistols where everyone says "don't shoot +P". I simply do not want to be in the grey area.

Thanks in advance!

+P is a reference to pressure NOT Velocity

Since loadings from different manufacturers use different powders, brass, primers and often projectiles (even if same weight) pressure curves are different. There is no direct correlation of velocity to pressure when none of the components are the same.

Trust the manufacturer's label, not the velocity of the projectile.

Using +P ammunition in quality firearms of good condition, though not recommended for +P, will accelerate wear on the firearm. Odds are the accidental use of +P in a firearm not rated for it will not cause a catastrophic failure provided it is in a firearm of good condition.

If the firearm is of questionable condition, it needs to be evaluated by a competent gunsmith to determine if it should stay in service or not no matter what the ammunition is.

Do Not use +P ammunition in firearms originally intended for black powder

BTW, I am not sure what your definition of an "older pistol" is, a few of the revolvers in my teaching inventory were made more than 60 years ago and still get several thousand rounds through them annually.

And if you run commercial ammo through your chronograph, you may find their advertised speed is obtained with a 10" test barrel, and does not match what you get in a real gun.
As a handloader, I can load a .38 +P with titegroup that is slower than the max non +P loaded with HS6. The specific powder matters in the pressure-MV relation. There is a SAAMI standard for PRESSURE, but not for what speed you get, since that depends on the specific powder used.

Editorial comment: If you buy the cheapest foreign ammo you can get without regard to where produced or to what standard, you may run into high variability in actual pressure, with a chance at a 'hot" batch. Also, US companies like Precision Delta and others offer .38 wadcutter ammo loaded light for target work, which is well below SAAMI max, if you want to be doubly safe.

__________________
Science plus Art

+1 to what the fine gentlemen responded.

Revolvers make their own ballistic laws - this is indisputable and well-known. If you want to know MV of some particular loading from your revolver, the only way is to buy yourself a chronograph. Regarding the supposed danger associated with shooting +P .38 Special, there isn't any. However, there is very little point in using anything other than standard velocity .38 Special loads 99% of the time. Do not confuse SAAMI chamber pressure with the actual chamber pressure of factory ammunition. SAAMI sets an upper limit, and manufacturers (at least the big ones) typically load to chamber pressures somewhat below the SAAMI limit.