I'm not quite sure I understand what is going on there. You were shooting 200's, which I assume are a weaker arrow? I am not that familiar with PSE arrows. And now you are shooting a 300, which is the next size up. How are you thinking the 200 and the 300 are going to the spine the same for that bow at that draw weight?
From the sounds of it you shortened your arrows to 24 inches to compensate? What were they before? If I have time I will run the numbers in Ontarget and see what it says you should be shooting.
What type of rest are you shooting that it lets you shoot that short of an arrow, you must be shooting with some overdraw in order to shoot 24 inch arrow with a 26 inch draw.
73lbs with a 26 inch draw lenght, crap dude! I draw like 55-60 lbs at that draw length. Are you sure your draw length isn't a bit short for you? You seem bigger than that to me.
Out of curiosity why did you change from the 200's to the 300's if it meant you had to shoot a shorter arrow?
As far as will it hurt your bow, no I highly doubt it. People keep forgetting to take into account the draw length. The minimum grains per pound rule is for a 30 inch draw length. You have a 26 inch draw length which means you are putting out way less energy. It would be the same thing as shooting less draw weight. You should technically be able to shoot whatever weight arrow that will give you what the bow is rated for IBO. If it is rated to handle the energy to push an arrow at 320 fps it should be able to handle it regardless of arrow weight. You are actually doing less harm to it because you are not using as much energy to get the lighter arrow to move that fast.
When people talk about shooting lighter arrows harming bows they normally mean shooting a lighter arrow to increase speeds beyond what the bow is supposed be rated for.
Using the AMO minimum weight chart I come up with around 350 grns for your minimum arrow weight. And this is AMO which is heavier than IBO.
So I think you are safe, especially if you have stuff on the string like silencers, nock and a peep sight. And using limb savers makes a big difference as well. I think with all the vibration reducing products we have now you could easily shoot a much ligher arrow than people think you can.
I think I shot some 200 some grn arrows out of my 350 dollar darton yukon when it was set at 68 lbs and 26.5 inches of draw. Didn't do a thing to it. I can't imagine what you are shooting will ruin your bow. Might not last as long if you shoot a lot though, and it's hell on strings so you might want to change those every season even if you think they don't need it. And if you use an STS type product I don't see them being great on your string either, so that's something to consider.
And your pro shop guy needs to buy a better calculator or take math again, because your arrows come out to 4 grns per pound and 4.5 grains per pound respectively. 344 divided by 73, it's not rocket science dude
. Maybe you can tutor him?
What is your set up? I will look and see if I can find it, but if I can't let me know what it is.
Make, model and year of bow.
Brace height
Axle to Axle
Type of cams
Rated IBO speed
Draw length
Measured Draw weight
Arrows
Shaft length
Tip weight
Type of fletching
Type of rest you are using and how far back it is set
What is on your string
I don't really need all of it though. I will search your posts and see if you list what you shoot somewhere though since you are not online right now.
Paul