** BROADHEADS ** Science & Math

[5MilesBack]

Yes, it absolutely does. That's the point. If you BH tune at 60 such that they hit dead on together at that range, broadheads will be higher at shorter ranges, lower at longer ranges. That's physics.

Of course, we know that. But living with and accepting a minor difference at 20 yards is much better than having BH's hitting several inches lower at our maximum distances. From my experience, after BH tuning at 60, those differences at closer distances don't even come into play. I would have to shoot several BH arrows at a horizontal line to come up with the difference at each yardage, but I already know they're pretty close as it is. But it's not worth it IMO since those arrows are always hitting the bullseye regardless whether they're a little tiny bit high.

 

[hobbes]

5miles sounds like you have significant experience shooting long range. I don't. As far as pins covering the target goes, I wear glasses for distance. They are relatively weak but enough to make the target clear and the pin have a halo. I hate it, but without them or any other option will do the reverse. I'm sure plenty of long range guys deal with it, but I've been considering smaller pins. You have any issues with blurry pins or Target at those ranges?

 

[dreamingWest]

No scientist but I do have a few documents that say I'm an engineer. However, if you don't use it you lose it, and I never do these calcs anymore and rarely think about them. This was stuff I survived back in the 90s. I don't think I'm off on my numbers based on velocity, but some of my reasoning may be off. A good student in college would eat my lunch on these calcs.

I love this comment. BS and MS in engineering here as well. Not quite as far removed from these equations so it's damned tempting to sharpen my pencil. I hate forgetting all the great aerodynamics I learned back in school. Those constant acceleration kinematic equations stick around though don't they!

I'm enjoying this conversation. I'm just getting into tuning bows and I wouldn't be able shoot good enough to verify any of these numbers. Dumbing it down for myself...this is like shooting two different bullets of the same weight with your scoped zeroed for one of them. They'll be really close for most "normal" hunting situations. But not adequate for real precision and will be dramatically different for long ranges.

 

[Beendare]

I've been able to get multiple bows to shoot BH's to the same POI at 50 yds through BH tuning. The reasoning behind this- the way it was described to me anyway- by some physics guys decades ago on the UC Berkeley archery team- friction from your BH is negligible at Bowhunting distances.

I've shot a fairly heavy arrow- 500 gr for many years. I do know that a lighter arrow is more affected by everything...and when we are talking a few % either way...that could also be a factor. In my case, it could be that my shooting wasn't good enough to discern a couple % variation in speed.

I've talked to Woody that did this ^ testing for Magnus above...he claims the friction on a 2 blade BH isn't enough to make a big difference. Personally I'm skeptical at very long distances.

Your test is interesting. I have no doubt there is more drag with some heads over others. I don't shoot BH's at an animal [-anymore-/grin] at longer distances. Years ago when I was testing this sort of long distance shooting I did see more drop at 80yd shots with my BH's.

The human factor must be considered as probably the biggest discrepancy in any result. Testing with a hooter shooter would be the ticket. First tuning with the hooter shooter to get both arrows hitting the same with BH's at a med distance, then let them fly at longer distances.

...

 

[5MilesBack]

I'm sure plenty of long range guys deal with it, but I've been considering smaller pins. You have any issues with blurry pins or Target at those ranges?

In lower light my pins blur up........the target is fine, unless my contacts blur up.......which does happen in our dry air and wind. At shoots sometimes I have to let down and try to clear my contact. I HATE letting down. Thankfully never have had to do that while hunting.....at least due to contacts.

I'm not a fan of small pins. I used to use the .010's for 3D but they never were bright enough for me in my Spot Hogg, even with the wrap. And if anything, I would be more inclined to use the smaller pins for up close......not far. I'm very good at spatial orientation, so being accurate with a larger pin at distance is pretty easy for me.

 

[5MilesBack]

Testing with a hooter shooter would be the ticket. First tuning with the hooter shooter to get both arrows hitting the same with BH's at a med distance, then let them fly at longer distances.

I would like to see the results of a perfectly BH tuned setup (at 100 yards) through a Hooter Shooter, and then see where that same BH hits at 20-90.

Every setup would be a little different, but would be interesting to see what different setups would show. I'm shooting a LH PSE Freak at 32 1/2" draw and 75lbs, with 520gr arrows at 296fps.......at least it used to be that. I've done a bunch of twisting/untwisting to get the bow close to where I want it now, and haven't put it on the scale or chrono since then.

 

[justin davis]

I would love to have a chronograph and a hooter shooter. Be fun to have those to mess around with.

 

[Tony Trietch]

Yes, it absolutely does. That's the point. If you BH tune at 60 such that they hit dead on together at that range, broadheads will be higher at shorter ranges, lower at longer ranges. That's physics.

But, based on your level of shooting, and your setup, you may not see the difference, especially at shorter ranges.

So, can you get broadheads and field points to hit together at your shooting ranges from a "practical" perspective? Yes, of course.

Can you get them to hit together exactly at all ranges? Not unless you're shooting in a vacuum.

Nailed it, this is exactly what I do. A couple inches high at 30 with bhs keeps both fps and bhs grouping together out to 100+. I would assume at 60-70 they are close to dead on in elevation and at 100 they might be an inch or two low. Both are within a limit that my shooting ability can't tell apart. This might not work for a top level tournament target shooter but for me, it flat out kills shit when I want it dead.

Thanks @RosinBag for the write up!

 

[RosinBag]

Rokslide is full of some smart people when I read through this. Those smart guys are sharpening pencils and talking in a way I have to read it two or three times to figure it out. That is good stuff.

My test was very crude in nature, and it had the human involved. But nonetheless, it showed what is happening.

If anyone wants to travel and spend a day with a shooting machine, let me know and we can figure out a time to make it happen. It is getting close to hunting season for most, but we have all winter, and winter in CA is not really a winter.

 

[Billy Goat]

I feel like we need a statistician.

I haven't gotten arrows to fly exactly the same at distance. Even culling and nock tuning you still have varible in spine to spine consistency between arrows. I would say typically 2" at 60 yards is about what I can get to. Point is trying to figure out what constitutes fly the same. I guess ultimately you unscrew the practice tip and put in a broadhead and see if that arrow hits the same hole. This is with a shooting machine of course.

 

[njyerg]

This makes sense now


Sent from my iPhone using Tapatalk

 

[sndmn11]

Who is going to test elevation and air density?!?

 

[justin davis]

Who is going to test elevation and air density?!?

It makes a difference. It makes a difference in my opinion. But it’s not a huge difference. I’ve tested it for my setup when I’m at 11,000 feet my arrow hits a few inches different at 70-80 yards than it does at 5,000 feet.

I think for the most part it’s not enough of a difference for the average guy to make a difference. The super accurate guys can tell a difference thou.

But it could definitely make a big difference I think for a guy coming from sea level and hunting high elevation.

Something to think about.

 

[Brendan]

Some elevation discussion from another thread referring to sight tapes pasted below...

Arrow flight and air density

All other variables being equal, what happens when someone has their arrow dialed in at 60/80/100 yards at sea level and then go to 14K feet? I figure at sea level, the higher air density would push the arrow around (and the vanes would have a lot to push against to keep flight corrected). I...

www.rokslide.com

You would also expect less difference between a broadhead and field point at Elevation and low humidity. Who knows if it'd be enough to tell though.

I remember reading this a long time ago, and as usual Randy Ulmer is thorough and easily understood. I found this on Archery Talk:

Here is Randy Ulmers take on the subject as well as a quick fix while in camp.​

​

At high elevation the air is thinner and gravity loses a small percentage of its pull. Every projectile slows more gradually and takes a flatter line. While baseball’s power hitters love the thin air of Denver’s Coors Field and professional golfers enjoy 10% more distance at Castle Pines just south of the city, this phenomenon is not a bowhunter’s friend. Sure, elevation flattens trajectory, reducing the effects of misjudged shot range, but all too often the knowledge comes as a surprise to the hunter at just the wrong time. If you hunt more than two thousand feet above the elevation where your bow was sighted in you will begin to notice that your arrows impact higher than normal. This can be a serious problem for bowhunters heading for the timberline from eastern states.​

​

The difference can be fairly large, several inches for arrows fletched with vanes and even more for arrows decked with feathers. Left unchecked, such a built-in accuracy bias can produce an outright miss, or worse.​

​

Of course the real key to remedying the problem is first understanding that it exists. After that, the physical solution is simple. Because the gap between the pins is affected, you can’t simply gang-adjust your entire sight head upward to account for the flatter trajectory. And, resetting every pin individually is too problematic in the constraints of most hunting camps. Instead, focus on one of your longest pin settings. Assuming it is 40 or 50 yards, set out a target at that distance and shoot until you are comfortable that you are executing good shots. Then simply turn your limb bolts out (reducing draw weight) in small increments until you are hitting dead-on at this range. Make sure to turn both bolts an equal amount in order to preserve the bow’s tiller setting.​

​

After making these adjustments move up and check your shorter-range pins just to be sure everything is still tracking. Your 20-yard impact point may be slightly below the intended target, but the difference will be so small that it is insignificant.​

​

Not only is elevation an important consideration when preparing yourself physically for the mountain hunt of a lifetime, it must also be considered when preparing your bow. Adjusting your draw weight is a​

step that can make a big difference in the outcome of the hunt.​

​

Caption: Hunting at altitude will affect your arrow’s point of impact. A small adjustment to your draw weight can quickly fix the problem.​

​

Tim Gillingham has talked about it before as well and changes his sight tapes accordingly.

 

[Brendan]

I haven't gotten arrows to fly exactly the same at distance. Even culling and nock tuning you still have varible in spine to spine consistency between arrows. I would say typically 2" at 60 yards is about what I can get to. Point is trying to figure out what constitutes fly the same. I guess ultimately you unscrew the practice tip and put in a broadhead and see if that arrow hits the same hole.

So, start with good arrows, .001 spine consistency. Check arrow specs in software like OnTarget2 or Archers Advantage, and make sure your arrow build shows ideal dynamic spine. Be meticulous building your arrows - cut from both ends, square both ends. Make sure inserts are square, field points and broadheads all spin true. I also spine check and spin test my arrows on a spine tester. I also have been known to test runout of each end of the arrow, broadheads and field points using a dial indicator. That's usually where I stop because at that point the arrows shoot better than I do, and all of this so far is easy to do in the basement if you have the tools.

Then, a couple things you can do. Number all your arrows, shoot bare shaft groups and nock tune every arrow. Easier out of a shooting machine, but doable at shorter ranges if you have good form. Then fletch based on results of nock tuning.

Also can do HIL testing (Look up Dudley's explanation). Again, easier with a shooting machine, but comes down to trying different dynamic spines (by varying rated arrow spine, point weight, arrow length, draw weight) and testing group size for your bow.

Another reason I need to make the time to build my own shooting machine. Found some good ideas recently I may finally follow up on.

 

[5MilesBack]

Who is going to test elevation and air density?!?

I test 6300 feet every day.

One year I took some really light arrows (for me anyway.......400gr) and at 11k feet there was a pretty sizeable difference between that and at home at 6300 feet. My heavier arrows don't show as much. But at 60-70 yards those light arrows were hitting 5-6" higher than at home.......consistently. That's huge IMO.

 

[Billy Goat]

So, start with good arrows, .001 spine consistency. Check arrow specs in software like OnTarget2 or Archers Advantage, and make sure your arrow build shows ideal dynamic spine. Be meticulous building your arrows - cut from both ends, square both ends. Make sure inserts are square, field points and broadheads all spin true. I also spine check and spin test my arrows on a spine tester. I also have been known to test runout of each end of the arrow, broadheads and field points using a dial indicator. That's usually where I stop because at that point the arrows shoot better than I do, and all of this so far is easy to do in the basement if you have the tools.

Then, a couple things you can do. Number all your arrows, shoot bare shaft groups and nock tune every arrow. Easier out of a shooting machine, but doable at shorter ranges if you have good form. Then fletch based on results of nock tuning.

Also can do HIL testing (Look up Dudley's explanation). Again, easier with a shooting machine, but comes down to trying different dynamic spines (by varying rated arrow spine, point weight, arrow length, draw weight) and testing group size for your bow.

Another reason I need to make the time to build my own shooting machine. Found some good ideas recently I may finally follow up on.

I already do everything you are saying. I used to spine align, but have stopped doing that. I run the shafts across the spine tester to check to see if any are terribly far out but then stop. I found I still had to rotate the nocks after spine alignment, so decided it was a step I wasn't benefiting from. I haven't found any arrows that have .001 spine consistency in a batch. I have .001 straightness. Aluminum arrows seem to be the most consistent on spine, but they still aren't identical. Now I think I could buy 3-4 dozen shafts, go through those and find 9-12 that are very close.

I do use the HIL testing method while setting up a bow.

Point is there are still inconsistencies in the arrows. They don't all shoot to the exact same point. In my experience. I have some a/c/c laying around that I'm thinking I'll play with a little. Maybe they will change my mind. But I'm not expecting it.

 

[elkstabber]

Excellent study by RosinBag and good analysis by hobbes. Rokslide is full of great info.

 

[hobbes]

It makes a difference. It makes a difference in my opinion. But it’s not a huge difference. I’ve tested it for my setup when I’m at 11,000 feet my arrow hits a few inches different at 70-80 yards than it does at 5,000 feet.

I think for the most part it’s not enough of a difference for the average guy to make a difference. The super accurate guys can tell a difference thou.

But it could definitely make a difference I think for a guy coming from sea level and hunting high elevation.

Justin, you may recall from back in my Bowsite days, but I used to live at 10,000 ft there in Leadville, CO. Sure made hunting higher elevation easier. I didn't do much testing of difference of arrow impact from 10,000 to 300 feet above sea level when I'd travel back to the Midwest (back home), but my shots there on whitetails were close.

However, one thing that I noticed at high elevation (completely apart from bowhunting) was that my turkey shotgun shot insanely good patterns that I'd never achieved with lead before or since. I'm convinced that it was related to the elevation.

 

[sndmn11]

I test 6300 feet every day.

One year I took some really light arrows (for me anyway.......400gr) and at 11k feet there was a pretty sizeable difference between that and at home at 6300 feet. My heavier arrows don't show as much. But at 60-70 yards those light arrows were hitting 5-6" higher than at home.......consistently. That's huge IMO.

I am wondering if there is a point where the additional drop with broadheads at range is compensated for with air densities at elevation?

IOW if one's pins sighted for field points at X elevation (I suppose a certain velocity would be needed as well) would be accurate with broadheads at Y elevation because the air resistance is less and ends up at a zero sum. Basically more surface area BH but thinner air = less surface area FP and denser air.