Pressure increases with hot chamber?

[haisardao]

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

 

[Eric H]

Bingo. If this is a hunting load, go for it as you should only need 2 shot max.

 

[haisardao]

Bingo. If this is a hunting load, go for it as you should only need 2 shot max.

Awesome, yes, it is x hunting. Funny never had that issue before.
Appreciate your input.

 

[cajun]

What weight bullet are you shooting?

 

[haisardao]

125 gr HHT

 

[Eric H]

That should be a crime what that will do to an animal. At least it'll be quick.

 

[haisardao]

That should be a crime what that will do to an animal. At least it'll be quick.

, the mesquite in TX is thick and thorny, I hate tracking deer!

 

[lancetkenyon]

RL26 is notorious for spiking pressure over 84°F.

Shoot 3, let it cool. Shouldn't be shooting 6 in a row at 3200+ anyway.

 

[haisardao]

RL26 is notorious for spiking pressure over 84°F.

Shoot 3, let it cool. Shouldn't be shooting 6 in a row at 3200+ anyway.

Oh I agree!, got carried away , trying to test this your groups are too small deal. Appreciate your input Lance.

 

[Brathany]

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.

 

[lancetkenyon]

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.

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?

 

[Brathany]

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?

Nope