Help with N340 for 9mm data discrepancy

[FJC]

I've been reloading 9mm for a while, and my favorite load has been a 124gr jacketed bullet (HP usually, RN sometimes) with 5.3gr of VV N340. I'm sure I've checked it against VV's data multiple times in the past. It runs great in my guns, and I've never seen any signs of overpressure.

I just downloaded their latest reloading guide, dated 2006. In it, they list 5 sets of data for 124gr 9mm loads. If I eliminate the lead bullet ones and another oddball bullet, there's this data:

124gr Hornady FMJ/FP, N340 min:5.3 max: 5.7
124gr Lapua FMJ-RN, N340 min: 4.5 max: 5.1 (huh?)
124gr Rainier RN, N340 min: 4.7 max: 5.1 (ok, it's a plated bullet)

So, why is the min and max powder level so much higher for a Hornady FMJ/FP than it is for a Lapua FMJ-RN? My current favorite load is OVER the max for two of those examples, and at the minimum for the third! I'm mostly using a Montana Gold jacketed HP...now I'm wondering if I'm at the top end (or exceeding) what I should be using...

 

[CZ57]

The length of the bullet shank, jacket mat'l and OACL are the prime factors. From an e-mail I received from V-Vs ballistician on another 9mm topic last year, he informed me that their then current load data is held to 32,000 PSI, but that's in the CIP (European) test method. In our SAAMI PSI system that would put it around 34,000 PSI, 1000 PSI less than the max for standard pressure. V-V does this because they are using minimum dimension barrels. That way if a pistolmaker is using tighter tolerances, or short chambers, you won't experience a significant pressure increase over their test pressure. You didn't mention what pistol/s you are using, but if they don't have extremely tight chambers/rifling, you don't have anything to worry about so long as you follow their recommendation for OACL which is 1.142"/29mm with the 124 gr. Hornady FMJFP. At one time the max load for this bullet with N-340 was significantly higher than the current max of 5.7. You've probably noticed that the European philosophy for loading the 9 X 19mm is quite different from American load manuals. I started using V-V 3N37 for 9mm in the early 90s and since then I tend to load performance type ammo with the longer OACL recommended by V-V and other European powder companies. Early V-V data was very close to the original pressure spec of the 9 X 19mm at 35,700 C.U.P. (36,300 PSI C.I.P.) which by todays SAAMI limit for +P is very close to the max of 38,500 PSI.

 

[FJC]

Thanks, good info. I guess as long as I'm happy with the round, and see no high-pressure indications, I'm good to go. It "feels" a little softer than WWB 115gr, but that doesn't really mean much.

I'm mostly shooting these out of Glock barrels, but do also fire them through a P226 and other 9mm pistols. It's just a bit frustrating trying to match up bullets to the right load data, with these variations. Montana Gold bullets do have a thicker jacket than many other bullets, but I have no idea if the core is harder or softer.

 

[CZ57]

FJC: The maximum loads I worked up with 3N37 were for my P-226 and my shooting partners Glock 19. Neither pistol has a short throat and if you want, you can work up to the current max load without any problem so long as you keep the 1.142" OACL. I used the 124 gr. XTP like V-V did, but I also used the Rem. 124 gr. JHP bulk bullet as well as the 124 gr. Golden Saber. These loads came from the #2 load guide and would be +P by SAAMI guidelines. 340 won't take you to velocities of 3N37 or N-350, but it's pretty close. 340 is also a great powder for high end .45 ACP loads. One load that I also worked up was the 147 gr. XTP with a max. charge of 3N37 for almost 1150 FPS in the P-226. V-V now has 3N38 that is probably better suited for the 147 gr. XTP. Their load takes the 147 gr. to over 1200 FPS at under 32,000 PSI (C.I.P.) and will work better if you use a longer OACL than the 1.142" recommended. 1.161" is the recommended OACL for the 9 X 21mm and you can use it in the SIG when building supersonic 147 gr. JHP loads. I'm not much of a fan of the subsonic loads. The W-W 115 gr. JHP load is rated at 1225 FPS last I checked, so your 115 gr. load is probably a bit slower.

 

[Ares45]

OT, but I've got to ask...Where did you get the 2006 VV guide? The Vihtavuori Lapua website still has the 2004 version. I've been looking for a more current one and would love to know where you found it.

TIA,

A45.

 

[FJC]

I got the 2006 guide from here:

http://www.lapua.com/vihtavuorinews.html

 

[Ares45]

Awesome! Thanks.