jszymczyk wrote:

" I don't know exactly the reason why the manufacturers do that."

In regard to most mono lines breaking at higher test than that stated on the label.

What I was told by the folks at Pure Fishing, which own Berkely, Stren, and Spiderwire, is that they don't EVER want a fisherman to return a spool of line claiming it was 'weaker' than the test stated on the spool. This started with the folks at Stren, before they were acquired by the forerunner of Pure Fishing. Stren used to claim that they had the 'strongest' fishing line. This was true, because they put fifteen pound line on a spool labeled at ten pounds. Their primary market was the burgeoning bass fishing anglers, and the tactic worked. In the early days of tournament bass fishing, most anglers used Stren, because they thought it was stronger.

In any event, it became an industry wide practice. This allowed for the bad knots, poor storage, and other after wholesale delivery conditions beyond their control, to not compromise the stated breaking strength of their lines.

I've had fresh 10 pound mono break at 18 pounds, and four pound mono break at 8 pounds. I've noticed differences in brands, Stren is still way under rated as far as breaking strength is concerned, with Magnathin being the closest (I don't think they make it anymore). Trilene XL is closer to rated test as well, but still significantly stronger than it says on the box.

I was also told by companies that make fly fishing tippet that this was the primary reason that tippet seemed to be stronger per stated diameter than ordinary fishing line. Tippet is usually rated closer to it's actual breaking strength, thus the wide difference between it and the regular mono.

The bottom line is this. If you care about the actual breaking strength to diameter ratio of your lines, leaders, and tippets, buy a scale and TEST them. Scales are inexpensive. A couple of hours testing your lines and your knots will be invaluable to you. You'll learn a lot, and be more confident of your gear.

Good Luck!

Buddy