ORIGINAL: Wyvern Crossbow
I think it's important to the image to Excalibur that they not miss lead hunters or shooters and I have never known them to miss lead customers with speeds that can't be obtained with normal hunting arrows. Some compamies use arrows that you can't hunt with or shoot on a regular basis to get their speeds, not Excalibur.
I hate to say it, but you are wrong here...Excal does not make, or sell a 350grain arrow. You cannot buy their bow, and their arrows, and achieve their "advertized" speeds. Will they get those speeds? yes, but I have to explain to my customers that the "305fps" listed on a Pheonix will really be 285ish with a "hunting weight arrow" even if they buy a "right stuff" package and use an "excalibur" arrow. I just pulled out another manufactures bow and came within 6fps of advertized speed with a slightly heavier than factory arrow. You cannot do that with an Excal. Though a great bow with many fine features and a great performer, their advertising is deceptive to the novice archer and TenPoint to be "competitive" did the same missleading advertising. I would sell more Excals and TenPoint recurves if the speeds listed could be achieved with the factory arrows and not some custom built arrow that is on the ragged edge of causing a dry fire...
Wyvern
I think that you need to rethink what you said above. In my statement I said that Excalibur uses Regular Hunting Arrows in their speed readings. As a regular hunting arrow,
That is an arrow which can be safely used and not under their recomended safety standards. The fact that they do not personally sell an arrow at that weight does not really matter, the fact is there are plenty of people that can build and sell them all the time. I bet I could contact more then a few different people on the internet and in a very short while have that weight arrow on the way to me if I want it. I bet if you even searched well enough you could find a store or two that sold arrows like that.
Now there are bow companies that use arrows to achieve arrow speeds that are under their min. safety weight restrictions. I can remember reading that these companies would actually print that if they used those arrows for hunting, not only would they risk injury and damage to their bows, but their warranty would be void.
Now this is totally deceiving!
As the dude said above, there are many variables in achieving arrow speeds. Now only does the string (type of) matter, it's brace height, arrow weight, type of fletch and most importantly the crono itself could be reading wrong. And I do like a company that sells their products with the safety in mind of the bow and purchaser. The standard string will not get those speeds, but they are more safe for the first timer or novice. If a mistake occures with these strings (more stretch in this string), there are likly less dammage to the bow or the shooter. A dryfire with this string and more then likely there will be no damage. If my memory is correct, it was reported that they dry fired, on purpose, over 30 times with this string and no damage (I believe with the 175 or 200lb bow).They have always stated that the shooter will need the faster strings to obtain the faster speeds.
Now I am not telling you how to do business but if your statement of that you could sell more Ten Points & Excaliburs if they sold that weight arrow, then I would be either building my own at that weight or getting them from someone else to include with the bows. It would probually raise the profit margin as well

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BTW, that weight of arrow with an Excalibur is not on the ragged edge of a dry fire. They can be shot and shot and shot because they are within their safety margin, put forth by them. With your thinking, I believe that your confusing them with the companies that use arrows which are under the safety margins for their speed tests.