7mm rem magnum accuracy issue

Afternoon all. So my son has a Tikka 7mm rem magnum. Pretty much over short time it has gone from same hole almost groups to 1.5 inch groups , same ammunition he’s used all along. Ive given the rifle a good clean, retorqued scope rings , mounts and action( 35lb on action).
It runs an older gunworks suppressor. Scope is a Vx5.
I found in the chamber a small “lump” of what I think was carbon , right on the edge of the shoulder. Ive cleaned that out.
Would that cause the accuracy issue? Or is is something ive missed. Any thoughts appreciated before I start changing scopes .Cheers in advance .

Are you sure you have all the carbon and COPPER out of the barrel ?

Make sure it hasn't developed a carbon ring

Well I think Ive cleaned it well. I did concentrate on the throat again after firing a few through it this morning. Is the carbon ring a common issue ?

Yeah and they are way more stubborn than you'd think. Difficult to get rid of without the right solvent and elbow grease.

I have a borescope if you want to chuck that down it and have a look.

Same factory ammunition, or the same batch of factory ammunition ? i

It can vary a lot from batch to batch

Can recommend bore bright for quickly and easily removing stubborn copper and carbon :thumbsup:

Its the same factory ammo Kiwi Greg ( Hornady prescision hunter )Ive used Boretech eliminator . I do have Boretech C2 copper cleaner as well in the shed. Should I try that or dare I say it Autosol metal polish.?
Ill see what happens tomorrow re grouping. If it persists I will look at borescoping it. Then I suppose it will be scope swaps.
Ill let you know , cheers so far.

Quote:

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Originally Posted by Chunk

Its the same factory ammo Kiwi Greg ( Hornady prescision hunter )Ive used Boretech eliminator . I do have Boretech C2 copper cleaner as well in the shed. Should I try that or dare I say it Autosol metal polish.?
Ill see what happens tomorrow re grouping. If it persists I will look at borescoping it. Then I suppose it will be scope swaps.
Ill let you know , cheers so far.

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I had stubborn copper a couple weeks back, 4 treatments with boretech copper cleaner barely touched it, 2 minutes with bore bright had it back to new.

Boretech eliminator will cause a clean patch to go bright blue when copper has fouled a barrel

Don’t forget to let it sit in the barrel for a good 30 mins before pushing the clean patch through

Check to make sure there is not pitting at the muzzle crown. Very common these days from leaving a suppressor on (even for just a multi day hunt if wet conditions)