Pressure issue with warm barrel???

[Wildwillalaska]

Shooting a new to me 308 today I had pressure signs arise mid-session while gun was warm and then went away when cool--with all ammo.

So gun is new to me. Heavy Krieger barrel, less than 850 rounds through the tube. Giving a general shake down, so was shooting a few different brands of match factory ammo, as well as a favorite loading of mine that seems to work in everything (43gr Varget with 175 Amax in Lapua brass) as well as a loading the grievous gentleman said worked for him.

Part way through my session, slow fire, but the barrel was warm, all the sudden the gun started having heavy lift and ejector swipe. I was shooting the slightly hotter recommended load, so immediately stepped down to my 43gr loading--same thing. Tried a couple of the factory rounds, same thing. Set the gun to the side while I shot another I had with me. Came back to it an hour later, and no pressure with any of the ammo after it had cooled.

Barrel was clean at the beginning of the session. Had about 25-28 rounds through it when pressure issue arose. Shot another 25 after it dolled without any issues. Gun shot ok, all one hole, but slight stringing.

Thoughts? gremlins?

Thanks,

Will

 

[MTyotehunter]

As your barrel warms up so does your chamber, you chamber a round and let it set there for a minute before you shoot and it warms to chamber temp 110* 120*F. This could be an explanation for your factory ammo. Good luck.

 

[-R-]

Ammo temps are more of an issue than actual barrel temp. Leaving ammo sitting out in the sun can cause fluctuations depending on the powder, Varget is usually pretty resilient to temperature swings.

How long were the rounds sitting in the chamber?

 

[Wildwillalaska]

My typical MO is to load 5 in mag, chamber, fire, open bolt, look at target, make any notes, etc, chamber round fire, open bolt, screw off, repeat. Once a round is in the chamber--it ain't long before the boom. Most my fiddlin around and stuff is between shots with bolt open.

Oh, and I'm in Alaska, so the ammo wasn't all too warm before it went into the mag. The factory rounds that also showed pressure were single loaded--so wouldn't think warming in the rifle is the cause--but possible.

I finally broke down and bought a bore scope--mostly for old lever guns--but guess I'll give this one a looksie when it comes in and see if there is anything apparent. Just strange how quickly it came on and how completely it went away. Shoot a fair amount, and various weapons and haven't experienced it before--why I'm scratching my head I guess.

 

[-R-]

You happen to have access to a chronograph to see if you're actually getting
an increase in MV?

 

[Wildwillalaska]

I had a magnetospeed with me--and had chrono"d several rounds a bit before. Reattaching and shooting through it would have made too much sense. Was curious after--and sense I had chrono'd what ammo I had with me, wish I had to see the difference. It was significant enough change I was very curious myself--but didn't check next time around if the issue repeats.

 

[KYpatriot]

Did you get any water or other foreign matter in the chamber, transferred there by the ammo?