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Temp sensitivity N320?


jstagn

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I was digging for exactly the same info mid-winter. The VV manual states their powders have a 1% velocity increase and 3% case pressure increase with each 18 degree (f) temperature increase. They don't specify a specific powder with this but rather leave it as a generalized statement -- perhaps because all of their powders share the same chemical basis.

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I always see people say that N320 is not temp sensitive. i disagree 100% with my own first hand experience.

In my CZ SP01, every year, when the temp drops to about 30-40 degrees, I lose about 20-30 fps. ( compared to 70-80 degrees ).

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my experience...

I live in central FL. A couple years ago I loaded my sons 9 minor loads with N320 at 129 PF (love that powder). I loaded my 9 major loads with Silhouette at 169-170 pf. Was at least in the 80's here temp-wise.

We went to the GA State match, and the morning we chrono'd, you could see your breath. He was 129 PF, I was 176. I'm a believer in the temp stability of N320 - at least for the areas I shoot in.

JimInFL

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The VV manual states their powders have a 1% velocity increase and 3% case pressure increase with each 18 degree (f) temperature increase.

In my CZ SP01, every year, when the temp drops to about 30-40 degrees, I lose about 20-30 fps. ( compared to 70-80 degrees ).

Which is approximately the 1% velocity decrease every 18 degree decrease noted above.

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The VV manual states their powders have a 1% velocity increase and 3% case pressure increase with each 18 degree (f) temperature increase.

In my CZ SP01, every year, when the temp drops to about 30-40 degrees, I lose about 20-30 fps. ( compared to 70-80 degrees ).

Which is approximately the 1% velocity decrease every 18 degree decrease noted above.

No change in my experience that would put me in a bind, but then again I don't load to 125.9 PF. Maybe the change in temp affects your barrel too, slowing down the bullet.

Edited by Red Ryder
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My personal experience with N320, shooting ten shot strings, is that the first rounds are always the slowest and the later rounds the fastest. I have always thought that the increase in velocity was related to the chamber and barrel heating up, and increased temperature due to heating of the subsequently chambered rounds.

I explained that to somebody who told me I was wrong, that the barrel heating caused expansion and therefore less friction to retard the bullet, but I would think you'd lose velocity because of gas blow by, but what do I know. I'll stick with round heating. ;^)

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  • 11 months later...

I always see people say that N320 is not temp sensitive. i disagree 100% with my own first hand experience.

In my CZ SP01, every year, when the temp drops to about 30-40 degrees, I lose about 20-30 fps. ( compared to 70-80 degrees ).

My experience has been similar.... n310 is a bit better, but not enough to make me change.

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