I was wondering if anybody could tell me how much of an effect if any shooting a load developed in 70 degrees in 35 degrees will have? I guess what I'm really wondering is,if I'm going to show up at the match and my groups are going to go from less than .5 moa to something way bigger? I'm using varget in a 223 with 80 smk's. Thanks in advance
varget, temp effect
- Thread starter boltman223
- Start date
The problem of shooting at a significant different temperature vs. load development is it might move you out of your accuracy node.
This is the reason why when you do load development, you find a node of significant “width†in terms of powder range and ideally you pick a powder charge that does not sit at either extremes of the node. This way, when shooting temp is significantly higher or lower, you are still in the node and not outside of it. In your specific case, since you developed your load, you are the only one who will be able to tell whether you are going to have a problem.
This is the reason why when you do load development, you find a node of significant “width†in terms of powder range and ideally you pick a powder charge that does not sit at either extremes of the node. This way, when shooting temp is significantly higher or lower, you are still in the node and not outside of it. In your specific case, since you developed your load, you are the only one who will be able to tell whether you are going to have a problem.
jlow said:
Yeah, I was wondering if a 35 degree temp change would have this kind of effect with varget.
jlow gave you good advice.
338 Mollett said:
Yes, I know it's is good advise but, I have not had time to do complete load development and do not have time to do anymore before Saturday. I just wanted to know what peoples experiences have been.
Jlow, thank you for the advise. you are right, we'll see and I think I will be alright.
My experience with Varget and current rifle is it performed horribly with a 17 degree temperature difference going from cooler to warmer. From sub MOA to + 2 at 100 yds!!! I get much better performance using other powders in roughly the same situation.
So much for Varget's "insensitivity to hot/cold temperatures"
Here is a VARGET example from a rifle I no longer have.
.308 Winchester
46.0 grains VARGET w/ Sierra 168 w/ 21" barrel
Zero degrees Fahrenheit -- pressure: 42983 PSI -- velocity: 2359 FPS
Fifty degrees Fahrenheit -- pressure: 46804 PSI -- velocity: 2426 FPS
Ninety-five degrees Fahrenheit -- pressure: 50518 PSI -- velocity: 2483 FPS
So, about 8% change in velocity, and about 9% change in pressure when going from zero degrees to ninety-five degrees.
Only thing for sure is hot ammo gets hotter when its hot, and weak ammo is weaker when its cold.
Probably didn't need a slide-rule to figure that one.
Well, that's usually the case but not always. The reverse can also happen.
AA4350 findings in .30-06.
70* weather the measured pressure was 47,100 CUP.
125* weather the measured pressure dropped to 45,100 CUP.
0* weather the measured pressure rose to 51,900 CUP.
Best thing to do is to simply test it and keep excellent records. Only time will tell.
So much for Varget's "insensitivity to hot/cold temperatures"
Here is a VARGET example from a rifle I no longer have.
.308 Winchester
46.0 grains VARGET w/ Sierra 168 w/ 21" barrel
Zero degrees Fahrenheit -- pressure: 42983 PSI -- velocity: 2359 FPS
Fifty degrees Fahrenheit -- pressure: 46804 PSI -- velocity: 2426 FPS
Ninety-five degrees Fahrenheit -- pressure: 50518 PSI -- velocity: 2483 FPS
So, about 8% change in velocity, and about 9% change in pressure when going from zero degrees to ninety-five degrees.
Only thing for sure is hot ammo gets hotter when its hot, and weak ammo is weaker when its cold.
Probably didn't need a slide-rule to figure that one.
Well, that's usually the case but not always. The reverse can also happen.
AA4350 findings in .30-06.
70* weather the measured pressure was 47,100 CUP.
125* weather the measured pressure dropped to 45,100 CUP.
0* weather the measured pressure rose to 51,900 CUP.
Best thing to do is to simply test it and keep excellent records. Only time will tell.
40 grs or Varget for a 168 gr bullet in a .308? It's a wonder the bullet ever got out of the barrel.
Varget is one of those powders that perform best when the case is full or nearly full; yours probably sounded like a cocktail shaker at the neighborhood bar.
I have been using Varget exclusively for the last 8+ years in .223 and .308. I shot the same loads in F-TR competitions year round. From around 35-40 degrees in winter to 100+ in summer. I'm happy with the performance, year round.
Varget is one of those powders that perform best when the case is full or nearly full; yours probably sounded like a cocktail shaker at the neighborhood bar.
I have been using Varget exclusively for the last 8+ years in .223 and .308. I shot the same loads in F-TR competitions year round. From around 35-40 degrees in winter to 100+ in summer. I'm happy with the performance, year round.
That was a typo.
Should be 46.0
Should be 46.0
I have run my Palma load (46.5 gr. Varget/BR4/Lapua case/155 2156 SMK) from 30 deg. to 90 deg. with less than three minute elevation change at 1000 yds. and I could not see any real world fall off in accuracy. Not that I am a great sling shooter but all seemed right with the world with the exception of a very cold trigger finger...
Humidity at the warmer temp was about 60% while more like 35% for the colder one.
Humidity at the warmer temp was about 60% while more like 35% for the colder one.
Actually, most of the difference in elevation is due to atmospheric conditions, not the powder.
At JBM, I used 3000FPS as the muzzle velocity for 30 degrees and 10% humidity and 90 degrees and 60% humidity. I used 1000 as elevation.
From a 100 yard zero, at 30 degrees, the drop is 30.5MOA. It's 28.1 MOA at 90 degrees. If the temperature differential of the powder had any effect it was about .5 MOA at 1000 yards; I would say that's pretty much negligible.
At JBM, I used 3000FPS as the muzzle velocity for 30 degrees and 10% humidity and 90 degrees and 60% humidity. I used 1000 as elevation.
From a 100 yard zero, at 30 degrees, the drop is 30.5MOA. It's 28.1 MOA at 90 degrees. If the temperature differential of the powder had any effect it was about .5 MOA at 1000 yards; I would say that's pretty much negligible.
Looking over my logbook I see I had 15-20 FPS difference from 25 and 102 degrees with Varget, a good ballistics program like Ballistic AE allows one to input the DA when the weapon was zeroed and current when DA when shooting
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