Lighten load with temp change

[Link]

Is there usually a need to lighten your load with a temp change from 70* to say 90* using 30.5gr of h4895 in a 6bra using a 105 class bullet?

ty Don

 

[butchlambert]

Well, I believe Jackie Schmidt upped his already hot ppc load when the temp rose.

 

[LHSmith]

From Gene Beggs ( Beggs tuner, shooting tunnel, 6mm and .22 Beggs cartridge fame) : For each 10* F rise adjust powder charge down by 0.3 grains, for each 10* drop adjust powder charge up by 0.3 grains. This is based on PPC/ BR capacity cases.

 

[butchlambert]

From Gene Beggs ( Beggs tuner, shooting tunnel, 6mm and .22 Beggs cartridge fame) : For each 10* F rise adjust powder charge down by 0.3 grains, for each 10* drop adjust powder charge up by 0.3 grains. This is based on PPC/ BR capacity cases.

I'm well aware of this and Gene is a good Buddy, but I'll defer to Jackie on this.

 

[savageshooter86]

Depends too on how wide of a “window” you have too

 

[paulT]

From Gene Beggs ( Beggs tuner, shooting tunnel, 6mm and .22 Beggs cartridge fame) : For each 10* F rise adjust powder charge down by 0.3 grains, for each 10* drop adjust powder charge up by 0.3 grains. This is based on PPC/ BR capacity cases.

Would .308 charge weight loads also be adjusted by 0.3 per 10 deg drop/rise
Thanks.

 

[CharlieNC]

Not if you work up the load when it's hot, might need to add when it becomes cooler.

 

[Link]

Depends too on how wide of a “window” you have too

Who can tell us how wide a ''average '' window is? I know it is dependent, but just a educated guess.

 

[CharlieNC]

Who can tell us how wide a ''average '' window is? I know it is dependent, but just a educated guess.

The node width refers to accuracy associated with barrel harmonics, but the pressure and therefore safety is still a function of temperature.

 

[dgeesaman]

Not if you work up the load when it's hot, might need to add when it becomes cooler.

I’ve struggled with this because of mirage on the hot days.

 

[JMayo]

I don't with varget & 6bra. Don't think 4895 is volatile on such a load ..

 

[Mulligan]

I am not a BRA shooter, so take this for what it is worth.

In my dashers, using H4895 with 103-108 gr bullets, a 20 degree change in temperature will require a change in powder charge to stay in tune.
CW

 

[JFrank]

I’ve struggled with this because of mirage on the hot days.

Yeah, been there.

 

[Bugs]

I am not a BRA shooter, so take this for what it is worth.

In my dashers, using H4895 with 103-108 gr bullets, a 20 degree change in temperature will require a change in powder charge to stay in tune.
CW

Good info. . . It would be interesting to know how much of a change in powder charge you had to make to stay in tune with such a temperature change.

Thanks in advance for the info.

 

[Ned Ludd]

The simplest way to determine how much powder charge should vary with respect to temperature is to record the velocity for a set load in different temperature conditions. It is usually not too difficult to find days in the spring/fall where it might be pretty cool in the morning or evening, or where the temperature is above average, so that you can collect velocity data over a sufficient range of temperatures in a relatively short period of time. Because we typically measure velocity using small samples sizes (i.e. n = 5), it is a generally good idea to collect velocity data often, so that a clear pattern will emerge that is minimally affected by the small sample sizes. From such collected data in my hands, the velocity/charge weight variance with powders such as Varget or H4895 usually falls in the range of about 0.1 gr per 10-20 degrees F in between around 40 to 90 degrees. However, such results can easily be different with other powders and/or cartridges and bullet weights.