Velocity Ranges in Colder weather using VV N320

[SubZer0]

After having trouble getting consistant flow through my powder measure, I switched to VV N320 using 180 gr bullets, at the recommendation of several people I shoot USPSA with.

I am trying to make major with a Glock 35 and after working up several loads starting at 3.9 grains and ending at 4.3 grains, the max listed, I ran them through my chronograph. Now in my experience I do not expect to get published velocities but these were way off. In fact, at 4.3 grains, the max velocity was off by 200 fps and didn't make major.

I was wondering if the weather would have this much of an affect? It was approximately 47 degrees and overcast.

On a side note, when I chrono'd my previous load they were within range of my previous documented velocities.

I like the VV powder since it measures so nicely, almost no variation between drops, and wondered what loads will make major? Would VV N340 work better?

Any help will be appreciated.

[G-ManBart]

The Sierra manual shows data for a 180gr JHP, 1.124" oal and a max of 5.2gr of N320 (1000fps). Based off that alone, you should be safe in working up in maybe .2gr steps to see if you can make major with it.

From my experience I've found that N320 tends to be pretty temp stable, but will increase velocity with an increase in temp and vice-versa...but not a large amount. R,

[olp73]

I am loading short length 40sw myself, but 5,3gr with an OAL of 1.124’’ sounds hot to me!! Set the bullet out as far as you can. Like 1.14(5). Expect to reach major some where between 4.5-4.8 gr. Work up 0.2gr at the time. Be careful, at some point the pressure will increase very fast. I don't think you will have any problems making major in a glock but look for pressure signs. Particularly bulges in the case heads if you are using a factory barrel. The barrel is not fully supported and the glocks have a tendency to lock up to early with hot 40 loads. (drag marks from the firing pin on the primer.)

340 will work better in the sense that you will make major easier, without the pressure spikes, but there is a reason why everybody are using fast powder in the 40. It will give less perceived recoil, at least that’s how the theory goes. I use 320 and have no problems, but if you want a little more margin you can use 330.

Good luck- and take care.

Edited November 27, 2008 by olp73

[SubZer0]

Thank you very much. I think I will start working up from 4.3 grains until I make major with a bit of wiggle room.

[G-ManBart]

Particularly bulges in the case heads if you are using a factory barrel. The barrel is not fully supported

Not really true. Take a Glock factory barrel for a G22, 23, 27, 35, put a case in it. Now do the same thing with a quality aftermarket barrel for something like a 1911 and see what difference there is in case support....very little difference at all. Only a small bit of case isn't supported on both and it's only marginally more in the Glock....and I am NOT a big Glock fan as they beat the heck out of my hands/fingers. Sure, there is a slight difference, but on either, it's supporting well into the web area and if one is going to blow out, it would in the other as well.

Glocks bulge the case because the chamber is larger in diameter for reliability, but when the round goes off, the case is touching the chamber all the way around...it's supported just fine, but is allowed to expand a couple thousandths more than a tight match chamber.

Here's a pic of a Schuemann Classic AET and a G22 barrel side-by-side for comparison. The glare from the flash makes it harder to see the exact line on the Schuemann, but it's enough to give the general idea:

[RegRob]

I was wondering if the weather would have this much of an affect? It was approximately 47 degrees and overcast.

I have been curious about the actual effect of temperature myself. One evening I took 20 rounds of major loads, N330 for my Glock 35, and put half of them in the freezer at the range, and the rest in my pocket. Waited two hours and quickly shot them over the crono. The freezer-group was about -18 centigrades, and the pocket-group was ab. + 30 centigrades. Average variation between the groups was a pf of 9,5, the freezer-loads barely making 170, the pocket-loads making just under 180. The freezer-loads showed slightly more variation than the pocket-loads, possibly because they gained temperature fast as I was trying to discharge them.

Anyone else with documented results from something similar?

Rob

Edited November 27, 2008 by RegRob

[SubZer0]

Excellent info! Thanks alot.

I loaded up VV N320 at 4.5, 4.7 & 4.9 grs with a 180 SXT and, as predicted, I hit 166 power factor with 4.5 grs and 170ish power factor with 4.7 grs.

I also bought some VV N340 and at 5.6 grains I was way into major with power factors in the 180's. Also, I see what everyone means with the "felt" or "perceived" recoil; N320 feels alot nicer and isn't as jerky. I'll definately us the N320.

I'm thinking 3.9 grains behind a 180 grain bullet for IDPA and 4.7grs for USPSA. Has anyone had any cycle problems at 3.9 grains, with a glock 22 or 35? My daughter shoots IDPA with me and a 11 years old it would be nice to hand her something with almost no recoil but that won't cause too many malfunctions, in a G22.

[JimInFL]

FWIW. I see the same as Bart. I loaded my sons minor with N320 and and chronoed them at 131PF, on an 86 degree day here in FL. On the chrono at Ga State (you that were there know what I mean) at 8AM (using handwarmers, it was so cold) they chronoed at 131 PF.

JimInFL