Pressure increases with hot chamber?

haisardao

haisardao

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Jul 15, 2022
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McAllen, TX
Hi all, I was shooting a load I developed for a 6.5 PRC, Lapua virgin brass, RL26 (57.0 gr), CCI BR2. Shooting suppressed at 3250 fps. I'm at least 1 gr below pressure according to the ladder test I did before.
Now the problem, firsts 3 shots all great, consistent velocity, 4-5 shot velocity spikes 40 fps more, 6 shot got an ejector mark and bolt lift.
I let the rifle cool off, and tried again, first shots perfect, then pressure spikes.
Have you seen this before? Never had an issue with Hogdons powders, I'm guessing RL26 doesn't like hot chambers.
Thanks
 
It's unlikely chamber temp is spiking the pressure. The chamber walls don't get the heat. I can fire strings of 25 by 1 shot per every 15 seconds and don't get pressure/velocity spikes. What will spike pressures/velocity is direct sunlight on the rounds if sitting directly in it. Then it's primer blowing time.
 
Brathany said:
It's unlikely chamber temp is spiking the pressure. The chamber walls don't get the heat. I can fire strings of 25 by 1 shot per every 15 seconds and don't get pressure/velocity spikes. What will spike pressures/velocity is direct sunlight on the rounds if sitting directly in it. Then it's primer blowing time.
Click to expand...
String of 25 in what chambering? 6.5PRC with RL26 pushing 3200+ is a warm load to begin with. And chamber heat ABSOLUTELY can cause rounds sitting in a very hot chamber to build pressure, same exact way rounds sitting in the sun heat up, but faster. Heat is heat. You ever feel a barrel after 5 shots vs one just sitting in the sun?
 
lancetkenyon said:
String of 25 in what chambering? 6.5PRC with RL26 pushing 3200+ is a warm load to begin with. And chamber heat ABSOLUTELY can cause rounds sitting in a very hot chamber to build pressure, same exact way rounds sitting in the sun heat up, but faster. Heat is heat. You ever feel a barrel after 5 shots vs one just sitting in the sun?
Click to expand...
Nope
 

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