Wes, a lot of reloaders remark that they don't get V-V's advertised velocities. When V-V powders first arrived in America, their loads were measured in the CIP PSI system, and still are but at lower pressure. The max loads for 9mm were very close to the original pressure spec for 9mm @ 35,700 Copper Units of Pressure at 36,300 PSI/CIP. In other words, very close to what SAAMI was describing as +P at 38,500 PSI. Just a few years prior, SAAMI had reduced the pressure rating of 9 X 19mm to 35,000 PSI/33,000 CUP. Our measurement system for PSI is different from the PSI system used by Commissione Internationale Permanente, CIP. The pressures are recorded at different locations in the chamber and are looking for slightly different values for comparison.
The SPEER Gold Dot factory +P load, along with its Black Hills counterpart, are two of the warmer factory 124 gr. +P loads you'll run across. If you pulled a bullet from the 124 gr. +P Gold Dot load, I suspect that you'd find one of two powders in commercial counterpart form, but possibly very close to what we buy as cannister grade: either V-V 3N37, or Ramshot Silhouette (formerly Winchester WAP) as sold to SPEER by Primex. This is only my opinion, and in my experience, Silhouette has lower flash than 3N37, but I know that the Primex powder is used for a number of factory loads.
The 7.0 gr. charge of 3N37 is warm, but Vihta Vouri has listed slightly higher in the past. Since the early days, they also began using minimum dimension chambers in their test barrels around load booklet #4. I use the #2 load booklet to work up +P loads with V-V 3N37. Since then, velocity has been a bit inflated as it's measured from actual pistols. I'm trying not to veer off too much, and hopefully I can bring this all together for a conclusion.
You mentioned that the 7.0 gr. charge felt lighter in recoil than the 6.5 gr. charge. That is a bit of a paradox, but I can think of a couple of possible scenarios. Typically, this powder is too consistent to have a velocity drop at a higher chargeweight. I won't say it's impossible, but I am going to dismiss it in favor of the two I'm considering. One being that as you went from the 5.5 gr. load to the 6.5 gr. load, you built up a bit more immunity to subjective recoil, but that's still a bit of a reach for the 7.0 gr. load. Is it possible that you went to the 7.0 gr. charge that you also went to V-V's longer recommendation for OACL @ 1.142"? When possible, that's the OACL I use for 124 gr. +P JHP loads. I use the Rem. 124 gr. JHP sold in bulk. An excellent penetrator that expands better with higher than factory level velocity. For a factory load, I use the SPEER 124 gr. +P Gold Dot. I've also used the Rem. 124 gr. Golden Saber quite a lot for this. No bullet performs better in my experience, but I get slightly better accuracy with the standard JHP.
Now we'll get to pistol specifics. When I load a +P 9 X 19mm load, I load it
specifically for the pistol it is to be fired in. So everyone should be aware that you can't jump right to Vihta Vouri's longer OACL recommendation. The Gold Dot factory loads I've measured have an OACL of around 1.120" with a tolerance range of +/- .005", sometimes a bit greater. In other words, OACL will vary from about 1.115" to 1.125", and that OACL is to ensure safety across the board with different 9mm pistols. As an example, the CZ 9mm pistols have short chambers, as do S&W 39/59 series pistols. For the CZ's, my 124 gr. JHP gets loaded to 1.125".
So how can you tell what the proper OACL should be for a specific pistol with your favorite bullet? Using a fired case, place your bullet into the case but just enough for the case to grasp the bullet. If it seems too loose, select another fired case until you get one that holds the bullet firmly enough for this test. Remove the barrel from the slide and place the "dummy" round into the chamber, then push on the rim until the casemouth seats in the chamber. The bullet/cartridge will be at maximum OACL. Repeat the process several times to ensure that the Max OACL is consistent. If the case is too tight, you may have to use a plastic mallet, tapping on the case rim. Then, you want to establish the amount of freebore that you want for safety.
I use .005", but IT IS NOT Arbitrary! Some pistols like the Glocks and SIG P-226 will allow very long OACL that will only be restricted by the 1.169" maximum for magazine function. I load my 9mm +P on a REDDING SS press that has a Top-Dead-Center feature and I use the REDDING titanium carbide dies with their separate taper crimp die in the 4 step mode. The tolerance range of my loads are +/- .001", so, if I want 1.142" as an OACL, my loads will run from 1.141 - 1.143". To load an OACL of 1.142", I want my dummy round to measure no less than 1.147" from the barrel in consideration. Again, this will vary with the OACL tolerance you can produce with your press so you may have to measure a number of rounds as you are loading them now to see what the tolerance range is, as produced with your press. Some progressives are better than others here, so I'm not trying to say that it is mandatory to use a Single Stage, just be sure you know what the actual tolerance range is! The longest cartridges will still need to be .005" shorter than the maximum allowable from the "dummy" round test. My method anyway. I've seen people use shorter, and somtimes without consideration of their press' tolerance range.
When you do this with the right powder, you can get match grade accuracy with +P loads. And yes, I do test them from a bench at the same distance I shoot them from handheld. With a good barrel, good loads come for me at sub 1" five shot groups @ 50'. More than adequate for combat distance. I have used 3N37 for this, as well as a number of others that are suitable in burn rate/pressure characteristics. Ramshot True Blue, HS-6, AA#7, Power Pistol, Blue Dot and Vectan SP-2. If minimum flash is also a consideration, I'd skip extruded flake propellants like Power Pistol, Blue Dot. Some of my most accurate high velocity loads have come with Blue Dot. Unfortunately, foot long muzzle flash has come along for the ride. Right now, I'm working with Ramshot Silhouette and so far, it is the lowest flash propellant I've used for this. Vectan SP-2 was very good, but no longer available. AA#7 is outstanding also, particularly with bullets 124 grains and higher, and with very low flash. If one is inclined to develop +P 147 gr. JHP loads, I doubt you can do better than AA#7 as far as velocity to pressure with low flash in the balance.
If any further assistance is required, send a PM.
