Thread: Typical cold/clean bore effect?

My 7mm08 (20 inch barrel) seems to consistently shoot about three inches low at 100 metres with SST 139g with a cold/clean bore compared to subsequent shots. Does this sound about right, or is there another possible explanation?

Originally Posted by MB

My 7mm08 (20 inch barrel) seems to consistently shoot about three inches low at 100 metres with SST 139g with a cold/clean bore compared to subsequent shots. Does this sound about right, or is there another possible explanation?

My 260 AI with uncoated bullets does 3" low and 1 " left for 2 rounds with cold clean bore @200 so yup sounds familiar.

When I coat my projectiles with HBN she is bang on but around 50fps slower than when fouled.


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Most of the rifles I have owned would always throw a clean bore shot at least a inch, so only hunt with a fouled rifle, go to the range and put gun straight back in safe and it’s all good to go for my next trip. haven’t noticed any affect of cold bore.

I have noticed that with clean bore the first shot is away from the main group, this is not unusual. So I generally just swab out the barrel with some kroil and only very rarely give it a full clean with copper cutter etc.

I had a 243 that put the first bullet from a cold bore (but not clean) well away from the main group usually about 2", I no longer own that rifle.

When I first got a Mossberg .308, I'd take it out, zero it, practice, take home and clean the bore.

Next time:"How has it lost it's zero"?

Re zero, take home, clean.

Next time: "How has it lost it's zero, didn't I do I properly last time "?

Eventually I caught on to the fact that when you clean the bore, you disrupt the conditions inside, and bust your zero.

I seldom clean the bore now, but when I do, I always re zero afterwards.

I look after all my rifles, but cleaning my bore is not something I do a lot.

My logic: Why clean the bore and change the bore condition, if it's shoot 0.5moa groups consistently? If you start losing accuracy, yeah clean it and see if that helps, otherwise, don't try and fix something that's not broken.

Just my opinion.

Cold bore shots is usually the person behind the rifle (sometimes takes me time to settle in as well). If cold bore shots was really a problem people would've been way less successful at hunting I think

Unless you have a sewer pipe for a barrel I juts put a light coat of oil down it. And a few pull through before I go for a hunt. Seems to work fine.

That is why we need semi's, so we can throw some lead around before getting down to the business of nailing the target.

Originally Posted by Max Headroom

When I first got a Mossberg .308, I'd take it out, zero it, practice, take home and clean the bore.

Next time:"How has it lost it's zero"?

Re zero, take home, clean.

Next time: "How has it lost it's zero, didn't I do I properly last time "?

Eventually I caught on to the fact that when you clean the bore, you disrupt the conditions inside, and bust your zero.

I seldom clean the bore now, but when I do, I always re zero afterwards.

That sounds very familiar, so thanks for that! Thanks for all the other replies too. I'll have to work something out. Just need some time on a range.

Originally Posted by DavidGunn

That is why we need semi's, so we can throw some lead around before getting down to the business of nailing the target.

Hahaha. I really hope that was tounge in cheek Dave

Originally Posted by Pengy

Hahaha. I really hope that was tounge in cheek Dave

happiness is a hot barrel

So what kind of cleaning are we talking about? Is the recommendation to not remove any carbon fouling at all after a range session and just put the gun away as is "until next time"?

Curious as I don't seem to experience this cold clean bore effect in my rifles and I do my best to get the carbon out after a shoot. I read in an old NRA target shooting manual that your cold bore shot should be inside your rifles grouping, ie it shouldn't sit outside of say a 5 shot group at 100 yards.

I personally only do the whole copper cleaning really anul bore cleaning scub the crud thing about every 3-4 years.....at the rate my rifles get fired thats maybe 20-50 shots....in between that time it gats a rag on jag with light oil or break free down it till comes out not black and put away.used next time and same again. cant say Ive ever missed an animal I can put down to first shot being off target......I will be off target but not the rifle.

I clean everything out of my barrels after each outing. Both Carbon & Copper. Cleaning rods, jags, patches, brushes, and solvent. Whether I shoot 5 rounds or a hundred. Clean bore shot is usually about a cm to the left at 100m.

It should only take one round to foul the barrel from a stripped clean barrel. If it takes more than a couple shots to return to zero after cleaning then that speaks about the barrels quality.
I would suggest that people clean their barrels unless there is no possibility of a fouling shot prior to hunting. In which case id still be inclined to throw some oil down it - which may or may not mess with your first round POI.