Bob,
Looking forward to a discussion, and not an argument. More than fine on my end.
First of all, I agree with you on momentum and penetration being highly important in bowhunting. Back in the "bad ol' days" (1980s and early 90s) when everyone was chasing the last possible fps, those 4-5" overdraws and soda straw arrows were "fast" (for then) but they sucked on game. The trajectory got flattened, no doubt, but at the expense of momentum and thus penetration.
Fortunately, that's changed. For me, hunting arrows need to be at least 400 grains and preferably heavier. I call it my "one ounce rule"; the hunting arrow needs to weigh about an ounce, maybe a bit more, before I'm comfortable trying to take game with it. 400 is also about the maximum distance I'm comfortable taking a shot with my long-range guns at unwounded game as well, but that's another discussion and seems to be another area where we agree. For comparison purposes, let's make it easy and set the standard arrow weight at 450 grains for later (much easier than 437.5
).
I also agree with you that a lot of the every year "newest/fastest/bestest" is marketing hype. There's no disagreement there. However, when you're talking differences over decades, it's not hype any longer. It's not that the older stuff doesn't work any more, it's that the stuff that much newer is so much more efficient.
That word, "efficient", is the key to the entire thing.
You're looking at the energy and speed issue as a 1:1 with no other factors. As with anything else in life, that's just not the case. Humans can't design machines that are perfectly efficient, and thus the losses in efficiency are where the "gains" in performance are made.
Now, I'll also say that I am NOT an engineer. However, I do know I can point back to certain changes that were big sea changes in the performance cycles of bows. One of the first was the use of FastFlite type strings/cables. The old steel cables and B50 strings were durable (and still are), but they are considerably more inefficient than the stings/cables of today. They were heavier, and that mass requires energy stored in the limbs to move it and thus robs it from moving the arrow, and they stretched more which robbed even more energy from being transferred.
A second was the change to the parallel and beyond parallel limb systems. The older bows, like what we saw in the 80s and early to mid 90s, had essentially the same profile design as recurves or long bows (some still had the recurve limbs; Golden Eagles and Hoyts were famous for this). When the design engineers started playing with the parallel limb designs, the efficiency increased. That, coupled with the weight-forward riser designs gave them the advantage of using longer limbs in the parallel design and reducing brace height (again increasing efficiency).
Add in the changes in limb materials and you get further increases in efficiency. Ditto that with the changes in cams. All that stuff adds up. In the mid-1980s, the AMO (60#, 30", 540 grain) speeds of bows were generally right at 210, with 220s being an absolute screamer (Darton was generally trying to push this envelope, along with PSE; often with a bit more than a grain of salt needed; the Hoyt "Rambo" was an honest 225 and that was one of the fastest of that era). The Martins and Bears I was shooting back then ran about 210 or so. Changing those speeds (210 fps) over to IBO (70#/30"/350) for comparison, you'd be looking at something like 290 fps. For comparison, and assuming that you were shooting a 350 grain arrow at 70# and a 30" draw on your Oneida for what would now be an IBO of 305, you had a bow that had an AMO rating of around 225 or so, which would have been about right for the Oneidas then.
The mid-1990s had AMO speeds at 220 and IBOs at 300 or a touch faster, and that wasn't uncommon at all as Bear and Golden Eagle and many others were honestly right in that range. That's not a huge difference, but that's largely before the new strings and parallel limb designs took over and before the dramatic changes in cams. Even still, if you took a 450 grain arrow and shot it from a 30", 70# 1980s bow with an AMO of 210 and an IBO of 290, and had that bow set up for hunting (string silencers, peep, etc.), you're going have it somewhere in the 240s; call it 245 fps. A 30", 70# 1990s bow set up the same but with an AMO of 220 and an IBO of 300 is going to give you that extra 10 fps (255 fps). 10 fps doesn't sound like much, but it's the difference between 60 ft.lbs and 0.49 lb/ft of momentum and 65-66 ft.lbs and 0.51 lb.ft. That's a pretty big difference on the receiving end with a roughly 10% increase in KE and a 5% increase in momentum. There was (and still is) a TON of game taken with bows set up just like that, so let's put the "1996 standard" at 65 ft.lbs, and .51 lbs/ft with a 450 grain arrow fired at 255 fps for comparison. Draw weight is irrelevant, but the delivered KE, momentum, and arrow weight, at shot velocity are not.
Now, you jump up to today's bows... IBO speeds are easily and honestly in the 340 fps range with more than a few beating that by a chunk. Take a 30", 70# bow with an IBO of 340, and you're going to fire that same 450 grain arrow at 300 fps pretty easily. Obviously, that's a huge difference in KE and momentum (90 ft.lbs and 0.6 lbs/ft, actually).
Just HOW LIGHT of a draw weight today is going to give you the same 255 fps with the 450 grain arrow to deliver the same KE and momentum that we "needed/had" in "1996", if the IBO rating of the bow is 340 fps? Honestly, it's not going to take more than 50#, maybe a touch less. Yes, really - 50#.
I'm shooting a 450 grain arrow right now from a bow with an IBO speed of 340, but at 29" draw length and 60#, and it's clocking 276 fps with 15 extra grains of weight on the string. That's a solid 20 fps advantage at 9# less draw weight an 1" less draw length than the "1996" bow. I also know that it's a very valid comparison because one of the old bows I'm shooting is from 1996 and it was a pretty high end, fast, bow for it's day. If I swapped out the limbs on this Prime for a set of 50-60# limbs and backed it down to target that 255 fps with a 450 grain arrow, I'd reach the lowest draw weight to do it, and maybe still be a touch faster.
340 IBO isn't even a screamer today. The bow that my local pro shop guy's wife is shooting has an IBO better than 350, and PSE (at least) makes a bow or two that go better than 360 fps IBO. You can drop way down in draw weight to get the same 450 grain, 255 fps, 65 ft.lbs, .51 lbs/ft performance that 70# of draw weight required 20 years ago. All of those newer bows do that more easily, and MUCH more quietly, because of the increases in efficiency over what we used to have.
One way you can very easily observe the changes in efficiency is just by listening. Take a bow from 20 years ago, take all the silencers and stuff off of it, and shoot it next to a "bare" bow of today (no silencers installed). The sound difference is dramatic. That noise you hear from the older bow is energy loss; energy stored by the limbs and released at the shot that does not get transferred to the arrow. That's speed that would otherwise have been there that just isn't because of the inefficiency of the design. The new bows are just better.
I talked to my friend Dan (dvdegeorge) here about this some months ago when I picked up the Prime I'm shooting now. I had been shooting that for about a week and had it dialed in pretty well. I got one of my older bows out and shot it during the same session. Now, the two bows are shooting almost identical arrow set-ups (less than 20 grains of weight difference). At the first shot with the old bow, the sound at the shot was so loud I pulled it down fast and looked it over because I thought something had broken. It was that much louder that it literally startled me. Dan laughed pretty good at that one because it took him some cajoling on his part to get me to try a new bow (I was in the "ain't broke, don't fix it; new stuff CAN'T be that much better" camp).
My neighbor was on his deck one afternoon when I was shooting in my yard. We got to talking afterward and he asked how I liked my new bow. He doesn't shoot and doesn't hunt and probably has never drawn a bow in his life, so the question surprised me. I asked him how he knew I got a new bow and he said he could here it when I practiced; "until a couple weeks ago, every time you shot, I could here the bow and then the arrow hit the target. Now, I just hear the arrow hit, so I figured you had to have gotten a new bow."
As for Oneidas; damn, they were fun and cool. They were, in their day, pretty quick (among the fastest). I think the fastest one that they ever produced was, logically, one of their last - the Stealth, or something like that. It was, IIRC, somewhere in the 320 IBO range and that's probably been 10-15 years ago at this point. One of my good friends from college is still shooting the Oneida he got back in the mid-1980s; same vintage as yours and shoots about where yours would have or did as far as speeds. Great bows; smooth (even today), but not very quiet or fast by today's standards. Still damned cool, though.
Now, WHY consider shooting a lighter draw weight bow today when obviously if you can shoot a 70# draw weight and get even MORE performance? Well, for me, it's several reasons. The game hasn't gotten arrow-proof over the years. In fact, with better broadheads (FIXED blades, thank you; still don't like mechanicals), they are less arrow-proof than they were. The ranges that I can honestly, ethically shoot game haven't really changed that much; 40 yards is about it and in most of the places I bowhunt 40 yards is a pretty long shot, so the extra fps isn't going to get me much more than a flatter trajectory and the arrow stuck further into the dirt or a tree on the offside.
Another big reason is wear-and-tear on the shoulders and elbows. Yes, I used to shoot heavy weight bows (considerably more than 70#), and yes, I still have bows that will go WAY higher than that. That stuff just hurts over time. A 60# bow puts less strain on my shoulders and elbow than does a 70# bow; 50# even less than that, etc. If I can draw it more easily, hold it more easily, and have it stress and strain my joints less, and STILL get equal or better performance than I got years back at a level that I KNOW kills stuff well, why wouldn't/shouldn't I?
