Recently I have bought HS Precision rifle in 338 Lapua Magnum caliber thinking that HS will give me better combination then Blazer R93 with 7 Rem Mag which I normally use for longer than usual shots. Unfortunately with 4 different types of bullets and different types of loads first 7-10 shots make very nice groups but after that groups start to go loose. I cooled the barrel obviously, try different loads and cartridges types but it is still the same result. I decided to clean the barrel after 7-10 shots but broke the extractor and have to wait to get a new one. Are anybody has the same experience? What it could be? Is it supposed to be like that?
Thanks

I didn't have any such experiences with mine. It shot well with several different loads. The extractor breaking begs the question of how hot the loads were.
You might try the fire one shot, clean, one shot, clean for 10 shots and see if you can get a better barrel break in..........................DJ

Thanks but what do you think what might be the reason? Extractor beeng broken obviously because I made a load a bit tough. Actualy Mauser 98 I have seems to be stronger because of its claw extractor.

My Remington 700 in 338 Lapua was a bit sensitive to being kept clean for the first 30 or so rounds, after that it settled down quite well.
As for the extractor breaking? No idea other than hot loads. What brass are you using?

Norma brass. You mean keep cleaning it until it gets better?

Brush "lapping" with J-B Bore Compound will accelerate the break-in process.

If the extractor is a Remington cir-clip type, the breaking is more likely due to poor heat-treating than abuse.

I have shot around 100 rounds already. Do you think it is not enough for breaking in the barrel?