How Much Extra Powder Constitutes +P Loads in these?

I know it is specific to calibers and weights of the bullets...and barrel lengths.
So, with "average barrel lengths" of pistols using these calibers, with these gr cast lead boolits, using WIN231 or near equivalent powders...how many extra (%?) .1, or .01 of powder would I need to add to make +P loads?

.32 acp 75gr..(max load per Lyman 48th is 2.5grs)
380 acp 102gr..........(max per Lyman's Cast Bullet Handbook 4th is 3.1grs)
9x18 Makarov 100gr...( " LCBH 4th is 3.7 )
9mm Luger 124gr.....( " Lyman's 48th is 4.3 )
40 S&W 180gr.........( " LCBH is 5.2)
.45 acp 200gr...........( " " is 6.0)

Too many variables in your question to give you a valid answer. One would need to use a pressure barrel and measure each load to have any kind of accuracy. "+P" is a pressure issue, which can be changed drastically by changing the cartridge overall length. Powder is only one of the factors. Case capacity affects pressure, and even that varies between cases from the same manufacturer in the same lots. Most, if not all, loading manuals will indicate pressure for each load they list. That would be the best place to begin to find the answers you are looking for. Bullets (or "boolits", sigh :smt011) also vary in weight and shape and will impact pressure levels. It's not just a matter of increasing the powder to make something +P. Check the manuals.

Sounds like you need a lot more experience prior to aiming for higher power loads.

Read the manuals and select powders that yield maximum velocity for a given bullet. Start at mid range or below. Use a chronograph to see where you are at relative to published data. Never exceed maximum charge.

Load light for the old military and antiques.

Yes,too many variables.Your posted 45 load is going to give a little over 900fps-in most guns,some may dip below that.While that load may work in my gun,in yours it could show signs of over pressure.That's why you start low and work up,your gun may not even let you get to a max load.If you want to go +P,you may have to go a little slower than 231,it isn't real fast burning but it is on the fast side,and fast means a quicker pressure curve.

At 1911Forum.com there's a guy named Nick and The Gerk that really know powders and reloading well,I don't know if they work in the industry but they know enough to.Ask them,they will know the answers for sure.

Also,if you're going to run a max load,have bulk of supplies,especially cases and powder.Rem brass is thin and Fed,Starline is thicker.A max load on the edge in Rem brass will have slightly higher pressure in the other.Powder also varries slightly from lot to lot,so if you get a different lot drop back a little and rework it back up to verify it's OK.Make damn sure you're not getting bullet setback also,a few thou isn't a big deal but any more can skyrocket pressure on fast powders.Don't change primers either,CCI can slightly increase pressure on some rounds.

All good advice, also WW231 may not be the best powder for some of the cartridges you asked about. My feeling is that if you need to go to +P, you may want to think about going up in caliber. +P in a .32 or .380 can be unpleasant to shoot in little guns, while a 9mm might give you more oomph with less recoil and better accuracy in a slightly bigger gun. You may also want to factor in things such as muzzle flash and blast.

I just found a short article in the July 2012 edition of Shooting Times Magazine entitled The +P Price by Allan Jones. This article gives information comparing standard loads with +P loads and the differences in pressure. It's an older edition but can probably be accessed by searching the title of the article or the author on the internet.

Another thing to consider is,is +P worth it? A 45 gains 2000 units of pressure (I don't recall if it was psi or cup) and about 200fps.

On a FMJ that can lead to more penetration that could be bad.On a HP it can mean under penetration.Self defense HPs have a velocity window they opperate in,and some are narrow.Too slow and it won't expand reliably (one of the Hornady HPs are known for it),and too fast gets shallow penetration because it opens fast.Where +P really comes into play is in short barreled guns like snubs and 3" autos in 9 and 45.While it's better than years ago,that velocity drop compared to a 5" barrel can make a HP not open or be unreliable.Most new bullet designs have a handle on this but a few are still borderline.

+P is also harder on the gun obviously.Just because a gun is rated for it doesn't mean it will live on it.Target guns run target loads for a reason,they last.1911s have run over 200K rounds as a target piece,that can be had with standard ball if the gun is built right,but I'd hazzard a guess you won't see near 100K with +P.HK USPs have eaten at 300K of ammo and they don't like wimpy ammo,but even though they are a tank I don't believe that would happen wlth +P.

As Sgt45 pointed out,the mouse calibers in a blowback operated gun won't be pleasant to shoot,and in this country I see no use for anything between a 22 and 380.

I personally wouldn't shoot +P in most of my guns. I might shoot +P .38 Spl. in my .357 but really see no need. If I wanted more power I'd just switch to .357 or another caliber. Some of the guns rated for +P (small revolvers, etc.) will handle some but a steady diet, in my opinion, would not be good for the gun. Again, just my two bits.

Thanks Guys,
My question was hypothetical in my quest for more knowledge~
(I've been shooting my reloads for "only" 3 years now)