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Literally. It was unusually hot for Southern CA yesterday. My favorite indoor range had HVAC problems, so the temperature was 95 F. This is the first time I was able to see the effects of high temperature.
I was there to tryout some loads for the premium 120 gr SS bullet from North Fork Technologies http://www.northforkbullets.com/mage...m-bonded-core/ Per the manufacturer's instructions, I backed off the typical load by 8% due to the bullet construction.
Using AA2520, I worked up to 28.5 gr and achieved a 3-shot average of 2575 fps with ES of 9. No signs of high pressure. So I will keep going to 29 gr in hopes of duplicating the commercial A-AMAX velocity (see below).
Also, I shot 5 of my 123 gr SST loads using AA2520 at 30.2 gr. These averaged 2667 fps with ES of 29. The high FPS in this group was 2708 ! I had ejector marks on the brass, but nothing that indicated extreme pressure.
I haven't recorded the 123 SST previously to compare, but 123 A-MAX on top of 30.0 gr AA2520 average 2609 when the AC is working.
As a control, and to sight in my new Vortex PST, I shot 6 commercial Hornady 123 A-MAX and recorded an average of 2600 fps with ES of 19. This compares to an average of 2567 fps when the AC is working.
So the ~20 F higher temperature accounted for an increase in about 30 fps.
Details:
24" Satern barrel (1:8.75) on Mega Billet receiver
Brass: Hornady (2x fired)
Primer: REM 7.5
Temp: 95 F
Wind: 0
Chronograph: Magnetospeed
I was there to tryout some loads for the premium 120 gr SS bullet from North Fork Technologies http://www.northforkbullets.com/mage...m-bonded-core/ Per the manufacturer's instructions, I backed off the typical load by 8% due to the bullet construction.
Using AA2520, I worked up to 28.5 gr and achieved a 3-shot average of 2575 fps with ES of 9. No signs of high pressure. So I will keep going to 29 gr in hopes of duplicating the commercial A-AMAX velocity (see below).
Also, I shot 5 of my 123 gr SST loads using AA2520 at 30.2 gr. These averaged 2667 fps with ES of 29. The high FPS in this group was 2708 ! I had ejector marks on the brass, but nothing that indicated extreme pressure.
I haven't recorded the 123 SST previously to compare, but 123 A-MAX on top of 30.0 gr AA2520 average 2609 when the AC is working.
As a control, and to sight in my new Vortex PST, I shot 6 commercial Hornady 123 A-MAX and recorded an average of 2600 fps with ES of 19. This compares to an average of 2567 fps when the AC is working.
So the ~20 F higher temperature accounted for an increase in about 30 fps.
Details:
24" Satern barrel (1:8.75) on Mega Billet receiver
Brass: Hornady (2x fired)
Primer: REM 7.5
Temp: 95 F
Wind: 0
Chronograph: Magnetospeed
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