Byron, +P+ suggests that pressure is higher than the max for +P at 38,500 PSI. To take this a step further, +P (38,500 PSI) is no higher in pressure than the original pressure spec for 9 X 19mm @ 35,700 Copper Units of Pressure, CUP. In my experience, the designation +P+ is usually used to indicate higher velocity, not necessarily higher pressure. Although I've seen 40,000 PSI mentioned as a suggested pressure limit for +P+, no actual limit exists. In the past, +P+ was also used as a designation for ammo restricted to LE Only. As an example, three of the best performing 115 gr. +P+ LE Only loads: Remington Secret Service load, Winchester Illinois Sate Police load and the Federal LE Only load, have velocity under 1300 FPS from service pistols. By handloading, you can achieve that without any need for even a +P designation. The ammomakers were pretty much trying to keep warmer 9mm loads away from those who might shoot them in their Antonio y Cleopatra 9mm made in Lowgradio Steelio, Spain. Powder and OACL are a couple of prime considerations. I would suspect that IMI would probably be one of the faster rounds available, but I'd have to see pressure data to believe it actually runs over 38,500 PSI, +P.
Personally, I like the Remington 124 gr. JHP. Its tougher jacket requires higher velocity for best performance. Your Uzi load may be FMJ and I have just never found a reason to buy FMJ when bulk JHPs run around the same price. The Rem JHP will work and function just as well as an FMJ and has a rounded ogive profile. Data is a critical aspect: you will need an older manual (i.e. SPEER #11) where 9 X 19mm pressure spec runs 35,700 CUP and no powder faster in burn rate than HS-6 should be contemplated, IMO. Vihta Vouri has 3 powders that are well suited for the purpose, N350, 3N37 and 3N38. If you can get ahold of their #2 load booklet, you won't have any problem building a load to match the IMI ammo. 3N38 was not available at that time. As far as American Powders, very few will push 9mm bullets faster than Alliant Blue Dot, Hodgdon HS-6, or AA#7 with bullets 124 grains and heavier. If you intend to continue using FMJ, you need to know what the maximum allowable Overall Cartridge Length is. A simpler approach would be to take the OACL from some IMI loads if you still have some on hand, and if you want to use their bullet, or something very similar in shape (Ogive). For the Remington 124 gr. JHP, I use an OACL of 1.142"/29mm, but you can go longer. I have loaded for a SIG P-226 using the OACL for 9 X 21mm @ 1.161"/29.5mm. I use several powders like V-V 3N37, HS-6, Blue Dot (If you like visual effects, aka muzzleflash) AA#7, Vectan SP-2 (not likely you'll find any) and Ramshot Silhouette. Hodgdon Longshot can be used, but I haven't used it. My suspicion is that IMI probably uses AA#7, but I can't confirm that. The slower burners will give you higher velocity in the longer tube of the Uzi.
I would recommend CCI-500 Primers and the only difference in quality 9mm and 9mm +P brass is the headstamp. I have reloaded +P+ brass, but I don't know a source other than factory ammo. I don't believe it is necessary unless you really want to exceed the original pressure spec of 9mm @ 35,700 PSI/38,500 PSI which is today's +P. Then you will find it very difficult to obtain data if, in fact, the case is constructed heavier as powder charges must be reduced for the lesser capacity. The same velocity can be achieved without exceeding actual +P pressure. You might also want to jump over to Brian Enos' Forum and look at how serious IPSC competitors load 9mm Major (definitely +P+), but very long OACLs are required because a good many of the loads go in to 1911 Race Guns and they load in standard brass. The powders I mentioned are top choices among IPSC competitors. Glocks are used as well; it and the SIG P-226 are only restricted in OACL by the magazine. Something the SEALs didn't inform the Army on when they selected the P-226, while the army chose the Beretta. Not bashing Berettas. I'm fond of the design and fired +P ammo in a Taurus PT 92 AF earlier today.
I can give you load data by PM if you give me some parameters: I like flash, I hate flash, FMJ, JHP etc.
