338 Lapua... clean cold vs fouled...

[highcountry2013]

So this may not be the correct section to ask this but...

I was breaking in my new Savage .338 LAP this week end and noticed quite a variation between the clean cold bore shots and the fouled shots...I know on all my rifles theres always a difference but this just seemed dramatic...

The load was a 300 gr Accubond with 83 gr of 7828...

The fouled shots were grouping 3.5-5 inches away from the cold clean bore group... both groups were .5" - .75" groups but landing on completely diff ends of the target...

Anybody else have this much of a defference between clean and fouled?

 

[supercrossbmx69]

Describe your cleaning process. Did you clean carbon and strip all the copper out as well or just clean the carbon fouling?

 

[highcountry2013]

For my break in i was using sweets then patches then bore gel then patches... cleaning every shot for first 20...

 

[Boss Hoss]

I use Krieger tubes and have several 338 Lapua based rifles and there is almost no change from clean or cold to warm.

 

[Deleted member 46119]

CCB = Clean Cold Bore
FCB = Fouled Cold Bore
FWB = Fouled Warm Bore
FHB = Fouled Hot Bore

So far my limited experience:

My factory barreled rifles seem to have a larger difference between CCB, FCB and FWB. Since the factory barrels are hunting rifles, just need to know what the POI shift is.

The 'custom' barrels seem to have less POI shift but most of these are pure target use so the first shot is to warm the barrel. My Krieger and Pac-Nors are pretty small shift.

Standard engineering stuff AIUI (anyone correct me if I get this wrong)

Of course it's all metallurgy. Slight variations in crystalline structure from one part of the barrel to another affect expansion under temperature shift which will change POI as the barrel warms. The premium barrels, by nature should be more consistent, it's what you are paying for.

When I get to the point that I am shooting a FHB, I believe the barrel is distorting rapidly as the barrel heats and cools between shots. We all know it's bad for the barrel. Sucks for accuracy. Why do I do it? I'm sometimes in a time limited competition format or I'm out shooting for fun and these are usually rifles I am waiting to rebarrel.

 

[Deleted member 46119]

Oh and for hunting I was taught to use FCB