Vit N570 and 560 - temp sensitive?

[Archery1973]

Is anybody notice a huge speed variation with these powders between 30 degrees and 70 degrees? I'm getting a 100 fps difference between those temps.

 

[FEENIX]

Is anybody notice a huge speed variation with these powders between 30 degrees and 70 degrees? I'm getting a 100 fps difference between those temps.

Check out #2 of http://www.longrangehunting.com/forums/f28/powder-temperature-sensitivity-31096/

 

[Birdhunter1]

I have been using 560 in my .243 with an 87 gr Vmax for about 6 years and I have not noticed a huge difference in pressure signs. I've shot from -5* up to 100* in elevations from 380-7000, have mostly always used Federal 210 match primers and when I have shot across a chrono I have always averaged out 5 shots at 3382 fps regardless of if it was 65* or 25*.
These numbers are all fresh in my mind as I was reviewing notes on my 243 load last night in preparation for an upcoming hunt to Wyoming in October.

 

[Outlaw6.0]

I use N570. Two cold bore shots chronographed at ~38* & ~65* measured a velocity difference of exactly 0.00fps. I understand two shots is a poor measurement but for a hunting rifle, cold bore variation is fairly important.... at least from what i'm told


In the same rifle, I also noticed little to no difference in MV from 80* to a LR shoot hosted close to 100*. YMMV.



t

 

[Archery1973]

That's interesting that none of you are having any speed variance.

I'm using N560 in a 6.5 WBY. I range from 3100 to 3150 from March to August.

I'm not sure what to do.

 

[Outlaw6.0]

50fps? It shouldn't be very hard to map the difference, provided it still shoots good. You could very easily carry a different drop card.



t

 

[Birdhunter1]

That's interesting that none of you are having any speed variance.

I'm using N560 in a 6.5 WBY. I range from 3100 to 3150 from March to August.

I'm not sure what to do.

Did you weigh out and sort the cases? Same lot # that cases came from?

Lots of factors could come into play, when I said above I averaged 3382 the range was 3412 on one shot that I remember and 3350 on another (possibly a different day, temp, case lot#, case brand case weight.... to be honest it has been quite a while). But 4 different times I have chrono'd that gun the average has come out to 3382 each time, if I had my notes in front of me or I would post them in the shot order.

With that 3382 average I have found to be a consistent group out to 700 yards, if there was a difference in the shots I fired at 700 yards it didn't cause enough difference to blow the group and I was still within minute of coyote kill zone at 700 yards.