Suppressors Condensation causing pressure spikes?

[5RWill]

Was shooting a mild load of 40.5gr of 4451 with 123gr scenars in my 18" 6.5x47 yesterday and it was cold. Shot groups the day before with no issues in rapid succession. Shooting quickly here though i had some stiff bolt lifts. Is it possible that heat from the chamber/barrel is causing condensation and some pressure spikes? Maybe i've overdone the CLP and it's found it's way into the chamber? It might be a dumb question but i've been googling to no avail. Let it cool/dry and i can shoot 4/5 rounds with no issue got to the 6th and 7th, fired and got a heavy bolt lift.

 

[OKbow87]

I had something similar to this happen to me the other day. I have a new 22 creed I did some ladder tests to find pressure with a couple powders the other day, then loaded some test loads. The loads and rifle had been in my garage where the lows at night had been getting into the teens and it was only getting up around freezing for highs during the day. I grabbed them and went out to shoot the test loads. My first 5 round group to get warmed up shots 1,2, and 3, were fine, 4 and 5 had slight sticky bolt. Every load I tested after that had sticky bolt even though they were 1.5 grains below where I found pressure during the ladder test. The gun sat for a bit and then I had 2 rounds left to check a zero after I took off the magneto speed and they had no pressure at all even though they were the same load I had been testing.

Only thing I could figure out was the extremely cold ammo was forming condensation on the outside when it went into the warm chamber. No other reason I could come up with for them to have pressure.

 

[SDet]

Temp sensativity of the powder. Powder at 20 degrees is fine, load it into a chamber at 100 degrees, let it sit for a second, boom higher pressure.
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[5RWill]

I'm 100% positive it's condensation. I pulled a fired case that had two beads of water on it the other day whilst shooting.

 

[MtnCreek]

I thought condensation was caused by lowering temp, not raising it.

 

[5RWill]

I thought condensation was caused by lowering temp, not raising it.

I thought it was just the interaction of water vapor between two different temperatures. Idk what else to call it though it sure isn't evaporation.. liquid in the chamber i guess? I wiped the bolt down and made sure there was no way a round was picking up lube off the bolt.

https://water.usgs.gov/edu/watercyclecondensation.html

The article references going from a cold environment with glasses in a car or something outside in the summer. Same premise i guess between the rounds in the chamber going from ambient temp which is cold to much warmer.

 

[supercorndogs]

Maybe a little frost on the case? Water would raise your pressure, being an incompressible liquid, it would effectively make your chamber smaller.

 

[5RWill]

Maybe a little frost on the case? Water would raise your pressure, being an incompressible liquid, it would effectively make your chamber smaller.

Exactly, though i've not noticed any frost at all. I mean they're pulled straight from the box to the mag into the chamber.

 

[j-huskey]

Moisture or oil in the chamber or case lube left on the case can cause pressure spikes in that it diminishes the chamber size but it also creates "bolt face thrust" in that it keeps the case from gripping the chamber wall, and the case slams back into the bolt face hard enough to cause ejector marks, some times case flow into the ejector hole (hard bolt lift and brass smear), and really flattened primers.
Mic 'ing fired case dimensions will tell you raised pressures or thrust.
Hope u find the cause and report back.