What is chronograph speed compared too ibo from manufacturer. Mathews Bowtec any kind? Bowtec blackKnight 342-350 feet per second ibo vs chrono. What is actual speed ?

Ibo speed is when they take an arrow 30 inches long, weighing 5 grains per inch, and shoot it out of a 30 inch bow pulling 70 pounds. This is the lightest possible weight it can shoot. And normally, the fastest speed the bow will produce. Now, the more arrow weight you have and the more stuff you have on your string, as well as if you let down your poundage, youre going to loose some of that speed. So, the speed your actually shooting depends on your setup.

My Patriot lists IBO speed between 320-328. My birth certificate said 320 fps. That is with a brass nock installed and the strings silencers and vibra blocks installed.

This is incorrect. The common IBO spec is a 70 pound bow, 30" draw length (generally, some manufacturers cheat since there actually is no such thing as an official IBO spec unlike the AMO/ATA spec), and an arrow weighing 5 grains per pound of draw weight..i.e. 350 grains.

Jeff, isnt that what i said? 70 pounds, 30 inch draw, 5 grains, 30 inch arrow. Not starting anything, just tryin to figure out what i put as wrong.

You had said 5 grains per inch not per pound. That is what he was saying is incorrect. I'm sure it was just a typo.

Just to further add to the discussion, generally speaking, most bows shot through a chronograph at "IBO specs" do not normally achieve their IBO speeds. There are many little tricks that manufacturers use to get any given model to shoot an impressive speed once or twice...or with just one unit of the model but rarely do the production bows shoot the actual listed IBO speeds.....with a few noteable exceptions.

ooooo, whoops, my bad.