Sticky bolt lift & extraction w/ very sooty necks

[Bulldog Firearms]

Had my rifle go down in a match a week ago where the rifle began to have sticky extraction & bolt lift. Ended up have to drive two cases out with a cleaning rod. I've had over pressure issues before where I've blown primers but I've never had issues with stuck cases or really belligerent bolt lift. Some cartridges bolt lift is totally normal and the sootiness is minimal, but when they're sooty they can be really hard.

Primers are fine. Went up to 45.5 grains on load development before started having pressure signs.

Load I'm using is
6mm Creed Lapua SRP
annealed, sized .002, run expander mandrel through
FGMM205M
44grs H4831SC
2.84 OAL
110 SMK
3050 fps

SD of 5 ES of 11.



What's going on?

 

[spife7980]

Are they resisting chambering initially?
When you extract an unfired round does the bullet have marks like it could be hitting a carbon ring?

 

[Precision Underground]

Any moisture anywhere possible?

 

[AIAW]

How many loads on that brass? I know you said you are annealing, but a possibility too is simply work-hardended brass that isn't expanding to seal off the gas, as sign which in turn could mean that the case isn't expanding against the chamber walls, causing excessive bolt thrust after firing. Carbon ring is also higher suspect like spife mentioned.

 

[Bulldog Firearms]

3 or 4 on brass. No resistance chambering. I hate cleaning because I've had some issues getting rifles to shoot decently afterwards. I've also had my eyes opened to carbon rings with 6mm stuff. Anyway I put some foaming bore cleaner down bore. Going to let it sit, go by work in morning and patch bore and go and shoot.

 

[Herstal 12]

Anneal necks and let us know if it cured the problem
Cheers

 

[Bulldog Firearms]

Anneal necks and let us know if it cured the problem
Cheers

I anneal every firing.

 

[Jake the dog]

Just throwing things out to see what might stick. All same brand of brass, same number of firings, trimmed to length the same?

 

[Milo 2.5]

3 or 4 on brass. No resistance chambering. I hate cleaning because I've had some issues getting rifles to shoot decently afterwards. I've also had my eyes opened to carbon rings with 6mm stuff. Anyway I put some foaming bore cleaner down bore. Going to let it sit, go by work in morning and patch bore and go and shoot.

You are definitely not getting a seal off, if it was not running 3050, I'd also say you were under pressured, but I do not think that is the case. You only showed pic of carbon on the shoulder, does the case body feel gritty too? Carbon on the shoulder usually does not equate to stiff bolt, but if the whole chamber gets gassed, then it can.
I would find a 44 cal bronze brush, or a 50 cal nylon brush, and somehow chuck a rod up in a drill, clean the chamber good with your foam, or Boretech C4 if you have it. If the shoulders of brass has that much buildup, it is in the same spot in your chamber, get it out and see if you get a seal.

 

[Bulldog Firearms]

Cleaned up the gun, velocity dropped from 3050 to 3025, groups stayed the same, but no sticky bolt lift and no sooty necks. Looks like I was having a carbon ring. Never cleaned the gun from the guy I bought it from.