From 8" groups to 1/2" groups

[bronxmurdock1]

Looking for your thoughts on this situation:

Recently took my rifle to a gunsmith to be stripped of DuraCoat and replaced with CeraKote. Also had the Smith mount a new Scope while he had the rifle (Steiner Tactical 3-12x56, Badger Ordnance Uni Mount).
Took my rifle out to the range today for the first time, and for the first 40 rounds I was shooting 5-8 inch groups all over the place. Then the groups got tighter and more responsive to corrections in the turrets. After about 50-60 rounds I was shooting 3/4 inch groups consistently and completed a successful tracking drill with the scope. After 140 rounds I feel my rifle is zeroed and consistently shooting 1/2 to 3/4 inch groups at 100 yards.

I would like to hear your thoughts as to what was going on with the rifle. The only two things I can come up with is: 1. Scope needed to settle in (Don't even know if that is possible, 2. The Smith didn't tighten the barrel all the way, and by shooting it the barrel fixed itself (Don't know if this is possible either).

Honestly, myself and the Range Officer were left scratching our heads. Any help would be appreciated.

 

[wareagle700]

Something wasn't tight. Go back over it and check mount cross bolts, ring cap screws, barrel nut, muzzle brake/FH. There should be no "settling in" that spans across 8".

 

[Trespasser]

Did he coat the barrel? I'm wondering if some of the overspray got into the bore or chamber of the barrel. It would explain why it improved over time as the coating was wearing away.

 

[bronxmurdock1]

So at the range and right now after cleaning I checked everything except for taking off the hand guard and checking the barrel nut. The Smith put the scope and mount on using blue locktite.

As for as the CeraKote, only the upper, lower, and hand guard were done. Everything else was left alone.

 

[17874]

I bet when he bead blasted it before Cerakote, the end of the bore wasn't plugged right and the end of the bore may have been blasted. By shooting it, you smoothed out and filled in the imperfections.

I may be wrong, but I have seen this happen before. Scope the end of the bore and see what you have.

 

[bronxmurdock1]

I bet when he bead blasted it before Cerakote, the end of the bore wasn't plugged right and the end of the bore may have been blasted. By shooting it, you smoothed out and filled in the imperfections.

I may be wrong, but I have seen this happen before. Scope the end of the bore and see what you have.

That might have happened.
I have a Titan comp indexed on and i don't think he took it off for bead blasting.

 

[Bill Larson]

yesterday my buddy went from 3" MOA TO .300" IN 6 SHOTS...... CLEAN BARREL TO DIRTY BARREL

 

[samnev]

yesterday my buddy went from 3" MOA TO .300" IN 6 SHOTS...... CLEAN BARREL TO DIRTY
BARREL

Had a similar problem. My 308 AIAW went from shooting 0.35 moa groups at one rage visit to 0.75 moa at best the next time. I had about 300 rounds on the rifle. Cleaned it and the next range visit back to 0.35 moa. I guess it does help to clean the bore once in a while.