So I was hoping one of you may be able to help me, I'm wondering how many FPS I could expect to gain going from 70# limbs to 80# limbs?

Thanks In advance

All things being equal, about 15-20fps. But you would probably now need to raise minimal arrow wieght from 350gr to 400gr.

In reality you might not gain anything or very little in the way of speed. Depending on the spine of your arrows you might have to bump up to a stiffer shaft which would mean a proprtionally heavier arrow. The thing you would gain would be kinetic energy and penetration, but just how much is necessary? A 70# bow will blow thru anything and put 10" of arrow in the ground. The arrow from an 80# bow will pass thru and put 14" in the ground. So what's the point unless you're planning a trip to Africa?

Thanks man, unfortunately they don't offer 80 pound limbs for my bowtech captain , do you kmow of anybody that makes limbs?
You have some great points , I am very new to bow shooting, just bought this bow about 3 weeks ago. My reasoning ( which may be dumb to you all) to want to make my bow faster , is to make it shoot the same spot on the target from 0-35 yards, so I was thinking hoping by making it faster, the arrow would fly the same path for a little longer before it started to drop off. Before i took it to the shop last week it was shooting 67 pounds, arrows were 5575s with 100 grain tips, I can't remember who they were made by though. The guy put more twists in my string and got the poundage up to 71,which changed the fps from 289 to 295, then I changed to the Easton flatline arrows with 85 grain tips and it chronod at 311fps. Before I could shoot out to about 27 yards before It started dropping, Now around 30-31 yards , so 4 more yards would be swell to make up for if you all kmow of anybody that could make or makes some heavier limbs could you tell me or link me? I'm shooting 3d targets all this summer to try and get to be a egret shot for next hunting season, thanks for all of your help so far it's really appreciated as I'm a real beginner to this

You have a slight misconception here. There is not a bow made that doesn't shoot an arrow that does not arc. The laws of physics are what they are and nothing can change them. An arrow is dropping from the time it leaves the bow till it hits something to stop it.

Yes, adding speed will diminish the drop to some extent, but not as much as you'd think. I've done my own shooting tests years ago to prove it to myself. I had a bow shooting 290 fps and sighted in at 35 yards. I bumped up the draw weight and shot the same arrow at 304 fps. Shooting the same 35 yards the difference in point of impact was just about 1 1/2" higher. Not enough to make much difference at any wild game animal or 3D target, and the toll on my shoulders told me it wasn't worth it either.

Also, I've tested several bows shooting a measely 264 fps that when sighted in for 25 yards placed an arrow into an area the size of a deer's vitals anywhere out to about 32 yards without holding high or low. Roughly 4" low at 32 yards. In practical terms I figured 30 yards to be acceptable at 3" low. So if I wanted to extend that to 35 yards I'd just sight the bow in at about 28 yards and have to hold about 3" low for short distances of 15 to 20 yards.

There are a lot of ways to bump up the speed. Cleaning any junk off the bowstring can help as can shooting a lighter arrow. If you're hunting mostly deer then arrow weight should not be an issue shooting at 70#. IMO jumping up to 80# is not the best solution.

thanks man! you have been a huge help!Ill just leave it alone and just practice practice practice.I have a 3d shoot this sunday so i gotta get it dialed in for the new arrows,I think ive got it pretty close though.I need to buy a good pair of binoculars for sighting the rings on the 3d targets because without them its impossible.Also the only thing i have left that i can think of is I need to get a stabilizer.Im going to be using this bow for hunting and competing so i dont want it so long that it gets hung up on stuff while walking thru the woods,but good enough to actually provide a difference ya know?

Thanks again,your help is greatly appreciated!