Josef,
The 8,81 is the proofing measurement of your barrel's inside diameter in milimeters, from top of land to top of opposing land. The Germans used/use a comma instead of a decimal point, as we do here in the States...
The accepted measurements are usually in the 8.81 to 8.84 range...(if I remember this correctly...).
Too small a measurement would probably pose safety concerns. Too large a measurement might lead to bullet/target inaccuracies...
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />