Five days ago I was out putting some final touches on my 9.3x62 CZ 550 American w/ 286 gr partitions @ 2500 fps. Zero'd at 217 yds the groups were running 1.5-2". Fired about 30 rounds.

This am I decided to run out again and check it's POI at further distances. First thing I did, as usual was check it's zero at 217 yes. Groups were all over the place and continued to get worse. I immediatly stopped, checked all the screws in the stock and scope; all tight. The only thing I can figure is a dirty bore increased groups to 5.5". Really threw my confidence in this rifle and now's not the time for that 'cause I leave for Nome in 20 days for a Grizzly hunt. I'd say I've got about 55 rounds through it and my last 3-shot group went 2-1/2". Ran out of ammo. Have to go back on Monday, buy some more Partitions and Big Game propellant and load up 'cause i'm not touching my picked over hunting loads I've set aside for the hunt.

If everything is tight as you say I would suspect a bedding problem.A proper glass bedding would be a good idea.

I think I discovered the culprit but won't know for sure until next time I take it out to shoot.

I bought this rifle used and the ownder told me he had run about 400 rounds through it but I didn't ask how or if he broke in the barrel.

In the past I dought I'd never run more than 30 rounds through it before ending my shooting session, then cleaning it at home. In the process of leaving a fouled bore before I hunt, I left it dirty this time after getting home. Adding the extra 25 rounds this am really added a ton of copper fouling.

Once I got home this am, I looked down the bore after a good scrubing w/ Hoppes #9 and I could see that every land was a golden color w/ copper. So I pull out my Barnes Copper remover and now I have shiny, silver, lands again. I've never seen white patches come out so blue before. In the beginning, they were dripping blue cleaner off the patches.

Wish me luck.

GSSP

I would also recommend that you clean the barrel with J&B bore paste.

That will get all the copper and carbon out of the barrel.

I hate to hunt in wet conditions with a fouled barrel as I feel the fouled bbl is much more susceptable to rust.

Lately I have been using a product called Prolix. It is a cleaner/lubricator.

After I clean my barrel I put a few wet patches of prolix in the bbl, let isset for a few minutes and then dry out the chamber and barrel.

So far on severfal different rifles the first shot out has been right on with the rest of the group.

Also, testing this concept at the range, I have cleaned several dirty bbls with only Prolix, drying them out, ads again the first round out is right in the main group.

This shows me that I can clean with prolix while on a hunt and not change my first round out.

Prolix is a Utah company:
ProChemCo

800-248-LUBE

You can get it from Heritage Arms in SLC.
[Well Midvale actually]

My CZ 9.3 has 508 rds. through it. It likes to be cleaned about every 40 rds. Mine shoots to the same point of impact clean or fouled so I hunt with it clean with a light coat of Eezox in the bore. Eezox is a great rust protectant that leaves a dry surface and doesn't change the point of impact. Good luck in Alaska and let us know how your 9.3 works on big bears.

Depands on the rifle I have some 223s that shoot hundreds of arounds and I never see a differants.

But then I have a 243 that one can besure that the 39th or 40th round. The group size opens way up. Run a brush and a couple of patchs with hoppes on it it rt back down to a .5 rifle. Not much fun fora p dog rifle but a great yote gun.

Yep! Copper fouling! Got the powder fouling out with Hoppes #9 and the copper fouling was quite evident. Ran the Barnes CR10 per the instructions. Took the copper right out. Back to the range where the accuracy went right back to sub MOA.

Breathing alot easier now with my Grizzly hunt in 4 days.