Varget vs Benchmark

[urbanrifleman]

As a former airframe mechanic and having flown aircraft, you're right . . . that's pretty obvious to us. With a gun the air density has very little, if any, effect on actual MV's of a projectile as it doe on the the projectile's velocity somewhere down range. Isn't that why one has to account for the actual MV when measured velocity using a chronograph that's set up 10 or 12 ft from the muzzle (when one wants to be really technical )?

The same air is in the barrel. I guess I would have to respectfully disagree. It does change. Pressure, humidity, etc etc effect the combustion and the forces on the bullet from the very beginning of the process.

There are changes even when the powder has zero temperature instability. Which there are powders now that are essentially near zero. Still velocity changes with weather.

But on the other end, claiming all powders are temp sensitive because velocity changes through the seasons, would also be incorrect. Which some have done.

 

[Straightshooter1]

The same air is in the barrel. I guess I would have to respectfully disagree. It does change. Pressure, humidity, etc etc effect the combustion and the forces on the bullet from the very beginning of the process.

Hmmm??? OK, let's look at the air in the barrel. First, if we look at the air involved with combustion, isn't it only the air trapped inside the cartridge when being loaded that's involved with the combustion process? Then, is the air inside the barrel really the same as the air outside the barrel . . . especially after firing a round or two (like, same temperature, humidity . . . density)?

There are changes even when the powder has zero temperature instability. Which there are powders now that are essentially near zero. Still velocity changes with weather.

But on the other end, claiming all powders are temp sensitive because velocity changes through the seasons, would also be incorrect. Which some have done.

Agree!

 

[urbanrifleman]

Hmmm??? OK, let's look at the air in the barrel. First, if we look at the air involved with combustion, isn't it only the air trapped inside the cartridge when being loaded that's involved with the combustion process? Then, is the air inside the barrel really the same as the air outside the barrel . . . especially after firing a round or two (like, same temperature, humidity . . . density)?


Agree!

The number of air molecules in the air as a whole are the same inside and outside of the barrel. The amount of molecules specifically create a pressure against the nose of the bullet. More air in the air makes the bullet go slower at a higher pressure

 

[jelenko]

The same air is in the barrel.

Right, through 24-30 inches but what effect is that going to have on MV?

 

[Straightshooter1]

The number of air molecules in the air as a whole are the same inside and outside of the barrel. The amount of molecules specifically create a pressure against the nose of the bullet. More air in the air makes the bullet go slower at a higher pressure

As I see it, as a barrel heats up, the air inside the bore is heated and becomes dryer. Hot dry air has low density therefore that air is less dense inside the bore than the air outside the barrel, even though air pressure inside and out is in equilibrium, . . . this density is especially divergent in humid climates. If one circulates the air through the bore, like using a barrel fan, then one can bring the bore's air density into equilibrium with the outside air.

Hmmm??? I guess if one could measure the humidity inside the bore and compare it to the outside humidity, then we'd know for sure.

This issue of heated air being less dense is a big deal for pilots . . . as we all too often see here at Phoenix Sky Harbor Airport during high heat of our summers.

 

[johara1]

You test under real world conditions and you will find is all hype.. Varget, H4895,and H4350 below 60 degrees down to 40 degrees drop at 1fps. per degree...... jim

 

[Dub]

You test under real world conditions and you will find is all hype.. Varget, H4895,and H4350 below 60 degrees down to 40 degrees drop at 1fps. per degree...... jim

that seems somewhat insignificant?

 

[johara1]

that seems somewhat insignificant?

Really?...... jim

 

[Dub]

yes

 

[johara1]

That insignificant amount as call it will take you out of the node..... jim

 

[urbanrifleman]

Here is some data from the old Hodgdon website. Data is old now but shows that clearly not all powders are the same.

For 308 with 168 match bullet:
POWDER TYPE/0-125* F EXTREME VELOCITY SPREAD (FPS)

1. H4350/4
2. Varget/8
3. H4831C/10
4. RL12/26
5. AA4350/29
6. AA2460/36
7. IMR4064/46
8. VV N550/49
9. RL15/50
10. VV N140/50
11. AA2520/63
12. IMR4350/ 67
13. RL22/75
14. RL19/94
15. AA3100/113
16. W748/114
17. VV N560/121
18. IMR4831/127
19. IMR4895/166

 

[urbanrifleman]

Independent testing. Clearly they are not "all the same"

 

[urbanrifleman]

I had another graph that I'm trying to find but I think I deleted it off my phone. It was the independent test done between reloader 15 and ar-comp. It showed reloader 15 changing something to the order of 120 ft per second over a hundred and twenty degrees and the ar-comp change something like eight feet per second. So they are not all the same

 

[johara1]

those are NOT real world condition test..... try it with in 60 degree day with. the rifle and ammo at the same temperature. then do it again at 40 degrees and you will see the the difference between laboratory bull shite and the real thing..... I did my test on a barrel that was shooting in a .1 and with the same loads in 80, 60 and 40 degrees and watched the accuracy deteriorate at 40 degrees because these powders fell off in velocity way more from 60 to 40 degrees. .... You can't do it right with it at 70 degrees and a gun that is at the same temperature and pulling shells out of a freezer at an other temperature ..... jim

 

[urbanrifleman]

those are NOT real world condition test..... try it with in 60 degree day with. the rifle and ammo at the same temperature. then do it again at 40 degrees and you will see the the difference between laboratory bull shite and the real thing..... I did my test on a barrel that was shooting in a .1 and with the same loads in 80, 60 and 40 degrees and watched the accuracy deteriorate at 40 degrees because these powders fell off in velocity way more from 60 to 40 degrees. .... You can't do it right with it at 70 degrees and a gun that is at the same temperature and pulling shells out of a freezer at an other temperature ..... jim

That's the air density. Not the powder. I'm sorry, it's not the powder doing that.

You can easily prove it too. Put your ammo on your heater vent on the way to the range. Or better yet, put it in a cooler at room temp from your house and go shoot in other conditions and it will still change.

Because it's not the powder.... air density is reducing the velocity.

When you TEST things you have to have CONSTANTS to do what we call "isolating the variables". And that isn't shite.

Like Ron Burgandy says.... "its science".

 

[johara1]

You tell that to someone that doesn't test any thing. So if its the air density it still makes drop velocity at 1 FPS. per degree not the bs. numbers you posted.... Had to go up in the load too get the same velocity..... jim

 

[kyreloader]

Still struggling to figure out how air density has anything to do with muzzle velocity.

What evidence do you have to back the conclusion?

 

[urbanrifleman]

Still struggling to figure out how air density has anything to do with muzzle velocity.

What evidence do you have to back the conclusion?

It doesn't. The only thing that matters is the temperature of the powder which immediately changes itself to whatever the ambient temperature is that day. And all powders are temperature sensitive the same amount. There are no other factors to bullet speed.

 

[johara1]

For us simple laymen that shoot all I know is what I test and find out for a fact is that the accuracy does drop off as the speed drops or increases with a given load due to temperature. You can term it any way you want it happens, and you need to adjust your load to get in to the node and back into shooting small. Everyone's favorite statement is you have to see it on the targeted at a 1000 it is easy to see zeroing in at Reade Range, the dirt flies when it gets cold, for those who believe their powder is insensitive to the temperature drop......jim

 

[jelenko]

It doesn't. The only thing that matters is the temperature of the powder which immediately changes itself to whatever the ambient temperature is that day. And all powders are temperature sensitive the same amount. There are no other factors to bullet speed.

Wait. In post 35, you said, "That's the air density. Not the powder. I'm sorry, it's not the powder doing that."