9mm Subsonic w/ 124gr and N340 possible?

[O_Blade_O]

Hi there,
I just got all my reloading equipment and making first batches of MY Ammo, what a satisfaction, after monthsworth of wait for a damn set of dies.

By the way, i'm on the other side of the pond and have all RCBS branded equipment, i like this stuff.
Here's my very first, all by me made ammo:

You can notice that is 9x21mm, not 9mm Luger, but it makes no differences for loads.
Now, these are made with a 124 grain RN FMJ Copper plated (100um plating, 0,004 inches), 4,7 grains of VithaVuori N340 as their loading manual (as for 9x21mm) says about as the starting load... and it is rated for 1140 fps.

I'd like to make a subsonic round with these components, as a beginner, i purchased a bulk of these.
I read on their manual that with a 4,5 grain of N340 powder should stay at 1186 fps...
How could i tweak it? 4,4 grains should go under the 1180 FPS barrier?

Thanks and sorry for all the questions! Thanks again.

 

[Walkalong]

Their on line data I have printed out for N340 shows a start charge of 4.7 for 1077 and a max of 5.1 for 1152 FPS with a Ranier 124 Gr RN.

You should be able to get what you want with N340, but N320 (or even N330) would be a better choice for lower velocities with that bullet, IMHO.

 

[ants]

My personal experience with 9x19, N340 can easily go down subsonic, but isn't very accurate. N320 is excellent when pushing 124g plated bullets to 1000 fps, and the velocities are very, very consistent. N310 is also very good at reduced velocities.

More importantly: The listed velocity in the manual is what they measured in the lab from a universal receiver, not a pistol. Your velocity will undoubtedly vary from the published data. In fact, you may already be below the 1180 barrier. You'll need a chronograph to test it. No other way to know your actual velocity, since the published data isn't an accurate predictor.

 

[O_Blade_O]

That's interesting.
A quicker powder for subsonic loads... i know there are your experiences but, what's the theory about that? I mean, how should be more accurate? Quicker powder has chanche to burn better before bullet leaves barrel, thus resulting in more uniform exit pressure while slower powders could have problems burning completely?

Sorry for the question but now it is in my mind

 

[Walkalong]

how should be more accurate?

It just is what it is. Sort of like math class. You did not have to understand the formula, just use it.

In general, powders will perform better at closer to max loads than really light loads. Not always, but it's good generality.

 

[rfwobbly]

Senor Blade -

Sometimes the minimum load shown is simply the energy it takes to operate the mechanism and has nothing to do with the bullet/powder combination. You didn't say what gun you shoot, but most guns come setup for +P self-defense ammo. If you'll install a lower spring weight on the recoil (slide) spring, you can shoot low power loads without fear of failure-to-feeds and stove-pipes. This may allow you to shoot VV's minimum load, or just a grain or 2 under that, with utter reliability. You can get such springs from numerous places, but one that comes to mind is Wolff Spring.

Let me also encourage you to look at N320 when shooting lower speeds. I regularly shoot 9x19 with 124gr on top of 3.8-4.0 gr of N320, with my CZ sprung at 12 pounds. Save the N330 and N340 for the 147gr bullets.

Hope this helps!

 

[O_Blade_O]

Thanks,
i have a CZ as in signature. It also comes with a softer spring, i'd use that. For now i made a batch with minimum load from VV and the 124 grain bullet.

I'd take in consideration taking some quicker powder... but it was just a curiosity if that was obtainable with the equipment that I already have, because as i said i purchased a good bulk of it, 3000 bullets and 1 KG of powder... may seem little but for me and my shooting frequency it's more than plenty.