Never tried the Blazer, I tended to use CCI Mini mags, quite a clean round. After 500+ through the barrel everything use to get a clean.
If I still shot at the range I would still take the H&K rifles over anything else, but like I mentioned before they are really hard to get hold of due to them not being made anymore. I believe Walther, Umerex had a spat with H&K over some copyright issues. Have a look on Guntrader might be some on there but you will still be paying £800 for a 2nd hand rifle, still worth it because of the build quality.