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7828ssc and an ever changing average velocity....

Mr.Knowit all

Hello,

It seems that every time I go to the range I get a different average in my FPS-like way different on the same loads. One day it will be 2954 with an SD of 8-12 fps, another day it will be 2929 with a similar SD. Then one day it was 2974 fps. 5 shot groups, same load, same box of ammo on some days. Double weighed every round and no other problems with other powders like H1000.
I know about the temp. sensitivity so I have been keeping track of the differences it temp. when I go shoot. Most days they are within 10 degrees or less of the prior shooting day so I have no idea why it would vary so much.
Does anyone else have a issue with 7828 like this? You think I should change my powder?

74 gr. 7828
CCI 250
ELDM 208s
Norma brass (new and shot before-same issue)


Thank you.
 
Mr.Knowit all said:
Hello,

It seems that every time I go to the range I get a different average in my FPS-like way different on the same loads. One day it will be 2954 with an SD of 8-12 fps, another day it will be 2929 with a similar SD. Then one day it was 2974 fps. 5 shot groups, same load, same box of ammo on some days. Double weighed every round and no other problems with other powders like H1000.
I know about the temp. sensitivity so I have been keeping track of the differences it temp. when I go shoot. Most days they are within 10 degrees or less of the prior shooting day so I have no idea why it would vary so much.
Does anyone else have a issue with 7828 like this? You think I should change my powder?

74 gr. 7828
CCI 250
ELDM 208s
Norma brass (new and shot before-same issue)


Thank you.
Click to expand...
I'm assuming you are loading 300 Win Mag. How much air space is in the case?
This can impact the performance characteristics of some powders.
Some powders other people claim is hugely temp sensitive (RL25, RL33) I run at 100% case capacity and have not had any issues.
 
So the bullet changes 1 fps per degree from density.

Then you add the powder change to that. Say this powder has a temp sensitivity of 1. That means it changes 1 fps per degree f.

So for 10 degrees you have 10 (density) plus 10 (powder) equal 20 fps.

Ar comp and r16 have a .1 rating. H1000 is like .2. Varget is .25, r15 is 1.25, and n160 is 1.5

But there are two factors happening at once.
received_397024841224765.png

So even with a totally temp stable powder you will see the change from density. But with a temp unstable powder you will see a big change as the two couple together.
 
Imr 7828 is one of the most temp sensitive powders on the whole chart Btw

It is 1.36
Compared to h1000 which is .21
 
Last edited:
Dusty Stevens said:
Powder adsorbs (not absorb) moisture and changes its volume and burn rate. Now your username fits a bit better :p
Click to expand...
Terry said:
Are you claiming this happens in loaded ammo.
Click to expand...
Okay @Dusty Stevens does the inside of a brass case do the same as the inside of your car's windshield when exposed to a rapid change in temps?
Will moisture build on the inside the case even when it is totally sealed? If I took a 300Win Mag case, primed it and seated a bullet (no powder), exposed it to temperature extremes over several days or weeks and then pulled the bullet would I find water droplets in the bullet puller?
I am pretty sure carbon acts as an adsobent but my thinking is the "damage" would be done (as far as the OP's concern) in the reloading process instead of at the range.
Care to expound?
 
Terry said:
Are you claiming this happens in loaded ammo.
Click to expand...
Yes
shoot4fun said:
Okay @Dusty Stevens does the inside of a brass case do the same as the inside of your car's windshield when exposed to a rapid change in temps?
Will moisture build on the inside the case even when it is totally sealed? If I took a 300Win Mag case, primed it and seated a bullet (no powder), exposed it to temperature extremes over several days or weeks and then pulled the bullet would I find water droplets in the bullet puller?
I am pretty sure carbon acts as an adsobent but my thinking is the "damage" would be done (as far as the OP's concern) in the reloading process instead of at the range.
Care to expound?
Click to expand...
Cases are not sealed. If they were there would be no need for sealant on bullets and primers where a life depended on it.
 
Dusty Stevens said:
Cases are not sealed. If they were there would be no need for sealant on bullets and primers where a life depended on it.
Click to expand...

So then, are powder manufacturers' (Hodgdon that I've seen most recently) warnings about leaving powder in a dispenser or powder measure without merit? I'm guilty of leaving 1/4 full chargemaster for more than a day between opportunities to test loads.
 
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