Velocity, copper tensile strength and fouling

[GetReal]

So, here's the deal....barrel fouls and loses accuracy in about 20 rounds .

Rds 1-10 groups about 1.25" (@ 100 yd, 5-shot grps)

Rds 10-20 groups 0.3 - 0.5" ( 2 grps of 5 rds)

Rds 20-25+ groups about 1.25"

Details:

6 Dasher F-class gun ... 32.0 +/- gr Varget... CCI 450 primers ... 2980-3000 fps... 105 Berger H.T.... Douglas 28" bbl 1: 7.5. I fl size, with neck bushings, anneal brass each time, careful brass prep, careful powder measure, LE Wilson chamber type seater dies etc etc etc


So, I'm wondering if my velocity is above the copper tensile strength and if I dropped my laod charge to 30.6 and 2850 fps (another accuracy node) if I'd get a wider accuracy "window"??

 

[Rat Rifle]

How many rounds on the barrel ?

 

[Sandstorm]

Are you using a bore scope to confirm a clean barrel.?

 

[GetReal]

500 rounds on bbl.

Yes, bore scoping bbl.

 

[GetReal]

UPDATE:

After talking to both Berger (shoot well in all my guns but this 6 Dasher ) and Compass Lake (built / spun bbls for my two others guns consistently under half moa) the consensus of both was either:


1. A tomato stake bbl, replace it or

2. Clean / lap bbl with JB bore paste. At this point....NOTHING to lose.

 

[mikecr]

A treatment of Tubb's FinalFinish, and WS2 coating of bullets plus WS2 dry prefouling.
You won't have to prefoul at all, much less with 10 wasted shots.
More shots before copper fouling out, if ever.