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Load Check - N320 and 170 Precision Moly - MINOR Load


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I just bought my first 40 and need some help picking a safe starting load. I have N320 that I have been loading in 9 and 45 and just bought some 170 grain Precision moly coated bullets to try. This combo is not in the VV manual and I am having trouble coming up with a starting load. I have searched the site and there is a lot of data for N320 and even the Precision bullets, but it's all for major loads. I am looking to start with a MINOR load for IDPA and Steel Challenge. The VV manual shows a starting load of 3.5 grains for a 180 LTC for a PF of 158. I know the lighter bullet should require more powder to achieve the same velocity, but since I'm looking for a lighter load, would it be safe to start with the 3.5 gr load with a 10 gr lighter bullet? My only concern is that the VV manual shows a starting load of 4.9 for a 165 TC-FMJ? I know the 5 gr lighter bullet and the fact that it's FMJ should dictate more powder than the lead 170 I am loading, but 1.4 gr seems like a lot. I am loading for a stock STI which should be able to handle longer OAL's then in the VV manual. I am considering something in between the load data for the 180 lead and the 165 FMJ (closer to the 180 since it is lead seems logical) and am considering this as a starting load:

3.9-4.0 N320

170 Precision

1.17 OAL

I would appreciate any thoughts on my approach. I know I will have to chrono to see what the combination is actually doing, but at this point I want to come up with a safe starting point that will allow me to get some rounds through my new toy safely. Certainly if anyone has any experience with N320 and a 170 lead bullet at minor velocity that would be most helpful. Thanks!

Edited by IceDevil
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Start with 180 data and don't try to interpolate.

Bullet Weight Powder Weight Velocity Note Power Factor COL

Bayou Bullet 180 N320 4.3 956 Major 172 1.130

Precision moly 180 N320 4.4 Accurate 0

Bayou Bullet 180 N320 4.5 942 Major 170 1.190

L-FP 180 N320 5.3 0

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I know the lighter bullet should require more powder to achieve the same velocity,

umm. what? I don't know that much about reloading, but that seems to go entirely against newtonian physics. Perhaps you meant it needs more powder to achieve the same power factor.... or perhaps I just don't know very m uch.

At any rate, there's a whole chapter in the Lee manual regarding reduced loads. You can do lots of interpolation and guesswork if you feel like it. Since you're shooting for minor anyway, you shouldn't have any real safety worries. I've used data for the next lighter and the next heavier weight if I couldn't find the one I wanted, and sort of guesstimated between them. Obviously this would be less safe working at max pressures.

I personally use 4.2gr of n320 behind a 165 gr jacketed bullet. I haven't chrono'd it yet, but it shoots light, and cycles the gun reliably every time, and also conveniently fits in the .5cc scoop that came with my dies. I'm still doing the slow 150/hr single-stage loading routine for the rest of the year, and the scoop works easier than the powder measure I currently own.

Note that for steel challenge, you don't even need to make minor, just a velocity IIRC, so you can just keep going lower and lower until it stops cycling reliably, then go back up til it cycles every time again.

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