Vv 320 & 330 Temp Coeff

[TreblePlink]

Not all powders increase pressure when warmer ... do VV 320 & 330 have a positive temp coefficient? If so, how dramatic is it? In .40 if I'm at pf 166 at 40F, am I likely to be safe at 60 F ?

My load is 5.5 of vv 330 using a precision coated rnfp 170 gr, at 1.178" oal. This is for a para 5".

[Glk21C]

from what I have tested in my .40 major loads with vv320, yes, but I am sure you will get all kinds of answers

[DougCarden]

I sure hope you dont plan to shoot any match that costs any money and have to chrono shooting a 166PF......if it is practice ammo or for local matches you should be OK.....it sucks to go minor at the chrono....

DougC

[TreblePlink]

Right. A better example might have been PF 169 at 40F. There IS an expectation that when warmer it will be stronger?

Reason I ask is I'm new to VV and I've heard that some powders have a negative temp factor, and I dont want to load up a big batch that chronos say, 169 at 40 F (like it is now) only to get worse during the warmer season.

I sure hope you dont plan to shoot any match that costs any money and have to chrono shooting a 166PF......if it is practice ammo or for local matches you should be OK.....it sucks to go minor at the chrono....

DougC

[DougCarden]

I know a lot of people that load VV powder and I havent experienced that as well. MY 175 PF load with VV320 is the same, whether it is 20 degrees now or 100 degrees in the summer, FWIW.

I understand your caution and applaud you!

Get ahold of Don Golembeski, he is a VV rep here in the US for more info.

DougC

Edited January 25, 2007 by DougC

[TCK]

I load vv320 in my .40 as well and I have not noticed any change thats climate related.

[kevin c]

I load N320 to about 170 PF with 180gr JHP's. Shooting 10 shot strings over my chrono, starting with a cold barrel, I consistently get lower velocity out of the first shot. I have not seen any progressive rise in velocity later in the string, though.

The change is so predictable that I routinely throw out the first shot value when calculating for average/SD/AD, but definitely take it into account for chrono'ing those three lonely little rounds at a major match, starting with a presumably cold gun.

I'll get the data from my log tonight, if you'd like the numbers.

[TreblePlink]

I guess I'm really asking about Winter / Summer differences, if any with VV. My previous experience with W231 leads me to expect higher pf with higher air temperature, but not all powders are this way ... I don't want to work up VV loads now that its cold without knowing what to expect in the spring and summer. I'm hearing most say that they really don't notice much change.

I load N320 to about 170 PF with 180gr JHP's. Shooting 10 shot strings over my chrono, starting with a cold barrel, I consistently get lower velocity out of the first shot. I have not seen any progressive rise in velocity later in the string, though.

The change is so predictable that I routinely throw out the first shot value when calculating for average/SD/AD, but definitely take it into account for chrono'ing those three lonely little rounds at a major match, starting with a presumably cold gun.

I'll get the data from my log tonight, if you'd like the numbers.

[kevin c]

If you're asking if the hotter temps in summer will make the ammo dangerously overpressure just from heating up in the sun, I don't think so (anybody with first hand knowlege to the contrary, please speak up).

A chambered round cooking in a hot barrel after shooting most of a long field course could get pretty hot, hotter than a round sitting in the sun, I'd guess. I haven't heard of guns blowing up from literally too hot ammo, so I don't think there is dangerously high pressure there. I also don't get shots late in a long string getting any faster (higher pressure) than the second or third shots. And for me those differences were only a couple per cent (10 to 20 fps).

The main consequence is not ammo that might blow up in hot weather, but more that an N320 load developed in the summer might shoot just a tad slower in the winter, so that those skirting the power factor floor might have trouble making declared PF unless they give themselves enough leeway (and most do, not just because of a possible positive temp coefficient, but because changes in altitude, chrono electronics, distance from the chrono - the dreaded chrono "voodoo" - can all affect recorded velocity, safe ammo or not).

That's my take on it, anyway.

kevin c

[Chuck Merriam]

From what I know from asking many more acomplished shooters is that the VV powders do not have a big flux with the temp, altitude, or weather. I have personally shot my 320 load in 80 and sunny on the coast, and 60 and rainy at 2000ft and neither had any difference. I will tell you that powders like Clays for example, have a big flux with altitude and temp. The higher price chases many away from VV powders, but for me the extreme predictability and performance keep me coming back every time. The VV powders also drop great in almost any loading machine.

[Mick]

I've been shooting N320 under a 180 @ 1.160" for about 10 years. A tech at the VV factory tested our load of 5.0 under the above load and found the loading density really good, the temperature great and it was a good all around load for pressure as well. I got that email back in the 90's and don't have it anymore. I've got one pistol with 114,000 rounds through it (two Scuemann barrels) and virtually all of that has been the N320 load. The load has never failed to make major or lose velocity like 231 did no matter what the temperature. In the summer it works as well as in the winter. My brass makes numerous loads and seems to last forever as long as it's shot in a good chamber. I tried Titegroup and it's OK but I think there just isn't a better powder for the long IPSC .40 loads. I've used it with 155 through 220s. I went through 20 or more pounds last year, the price just keeps going up but I'm not switching!

[Paradox]

In East Texas, I make 168-169PF with 4.3gr N320 @ 1.180" (~100+ deg.F). This time of year it takes about .5gr more to make the same PF (~35 deg.F). If I anticipate shooting a big match in colder weather, I bump the charge accordingly. I am pretty sure David Re shoots the same combo and has similar experiences - he has mentioned it in several threads.

From the voice of experience: Life at the chrono became easier once I kept a detailed spreadsheet of load data and ambient temperature / humidity when I chronograph.