Elevation accuracy

[dotman]

Has any one else noticed they need to fine tune their bow when going from 1000ft to 11000ft? I agree that it sounds crazy and everything tells me it is too short of a shooting distance in archery to see any change but seems like every year I have to adjust for a few inchs in drop from what my bow is set at here in KC to the high country of CO.

When I return home I have to adjust back. So am I just crazy or has anyone else noticed this, I want to point out it isn't a huge adj and if left alone would still be in the kill zone.

 

[Maxhunter]

I live in Utah and I've never had to change anything. I had a buddy thought come from a state below 1000ft in elevation and he had to adjust his sights.

 

[Backpack Hunter]

Never had to change at that elevation, but when I come from 2,000 to 10,000ft I have to change.

 

[dotman]

Ok so i'm not crazy

 

[RosinBag]

So I may have spurred Dotman to start this thread....

This is a widely debated subject with many different results for individuals. Here is what I have read, experimented and learned from world class archers and hunters.

For 95% of most archers shooting modern equipment the difference in elevation is minute and this is why. If you take into account elevation, you also must take into account temperature. Lower elevations are usually warmer than higher elevations, so some of the elevation difference is negated by the temperature change. The time of flight, time the arrow is in the air, on shots say under 50 yards is so short there isn't enough time for the differences in elevation and air temperature to effect the arrow significantly. That is the simple explanation, there are more wordy scientific explanations out there, but this should work.

Remember I said 95% of archers. Recurve, longbow or archers shooting slower bows, say 250 FPS or slower could actually see differences at longer ranges due to longer time of flight and their slower speeds.

An archer would need to be able to shoot groups in the 3" range at about 60 yards to even see the effect of elevation and it wouldn't be much, probably somewhere around an inch or two at 60 yards. For 95% of us, we can't see that difference as we can't shoot that well. At 60 yards, shooting a 5" spot, I may have a couple in the top of the spot, a couple in the bottom, one a little left and one in the middle. Say a 6" group, how would I tell which one the elevation was effecting with that type of grouping? I can't, but I know the animal I am shooting at is hit in the lungs and will die.

I shoot at 130' elevation for most of my practice. When hunting, the trailheads I hunt from to start my hunts are at 5000' and 8500'. I take my broad head target every year and send a few arrows downrange prior to heading out into the wilderness. At 40 yards, I will shoot all of my arrows into the lungs on a deer target without any problems due to elevation. And at 40 yards with broadheads, I typically shoot about a 4" group if I shoot the arrows well. I also shoot my arrow at 294 FPS. I know I am not in any type of world class archer status, so I fall into the majority.

A few years back Randy Ulmer, who I do consider a world class archer wrote an article on this very subject. I don't have it, but maybe someone can track it down and post it up. I don't remember it word for word, but this is what stood out to me. He made an adjustment in his set up due to significant elevation change. That adjustment was a half turn out of his limb bolts on a Hoyt shooting 300 FPS. That would equate to 1 to 1.5 pounds off of his draw weight or about 3 to 4 FPS reduction in arrow speed. Randy is an archer who can shoot well enough to see that difference at longer yardages.

Try that out. Go to say 40 yards and shoot a group of arrows, take a half turn out of your limb bolts, and shoot another group without pulling your arrows or marking them. When you went down to your target, I would say that 95% of us wouldn't know which ones were which.

I am not saying your crazy either about your arrows shooting a little high when you get into higher elevations on a hunt. But it may not be the elevation. It could be excitement, nerves, anticipation or you could be a 5% that is an excellent archer.

This is not that dissimilar to exterior ballistics in rifles. Time of flight is critical elevation effect on the bullet. That is why bullets with higher speeds and better ballistic coefficients are less effected than slower bullets with lower ballistic coefficients. Most flat shooting rifles don't need to start taking into account elevation change until about the 450 to 500 yard range based on all the same information.

And like anything on a forum, just my opinion based on my experiences.

 

[dotman]

I would say I haven't ever seen a huge diff but I like to have my bow hit where I aim and a 3in diff at 50 or 60 bugs me. I agree that it doesn't change much and I do not notice it at short distances but past 50 it shows up more. I have no clue what speeds my bow is shooting, never got caught up in that but it is rated for 300+ from the mfg. My house where I practice is at just over 1000ft, humid and very hot before I head west where there is no humidity and temps are 30* less on avg plus. I also shoot an arrow weight of 439.

You do notice the diff if you practice a lot because your grouping changes from where you usually would group. yup Rosin you spurred it on and it is a good topic to consider.

 

[RosinBag]

Hopefully Dotman you meant 3 inches high and not "drop" at 50 or 60. I would think coming from 1k to 11k you would be high with point of impact compared to your pins.

This topic is always a good thread. We can get 100's of different outcomes as everyone shoots differently and each of those are their own little experiment.

 

[dotman]

Haha yeah, I corrected

Also it wasn't just me my buddy went out with me on his first western hunt and his bow did the exact same thing.

 

[dotman]

So do you think humidity would play into this at all?

 

[RosinBag]

I think it could be a factor....humidity is how much water vapor is in the air, so that could effect speed. That is why you have to take into consideration all environmental factors. If sighted in absent of all of these other factors, you could see point of impact differences when you go someplace that has many. That is why I believe it just can't be elevation only that effects people, it is combination of all the environmental factors that have changed along with their excitedness, nervousness and other human factors.

 

[bohntr]

I live at exactly 13' above sea level. Without exception, when I travel to trail head in the high-country (11,000') and practice there before ascending, I find when I'm shooting at 3" orange dots I am consistently 1-1.5" high at 40 yards. While that's theoretically still a dead deer, I adjust my entire sight slightly until I'm in the spot and then check shorter and longer yardages. Reason being, is I usually plan on ascending an additional 1000' where the deer are and want to be as accurate and confident as I can.

 

[HellsCanyon]

I doubt humidity will have an effect on arrows. Going from 0 to 100% humidity only has an inch or two difference at 1000 yards for my rifle. Your two biggest environmental factors are elevation and temp for this subject....

Mike

 

[RosinBag]

I think Bohntr (Roy) has a pretty good practical experience in how elevation will effect point of impact. Roy went 11k feet and at 40 yards was 1 to 1.5" high. If memory serves me right, the last time I saw Roy cast an arrow it was going about 280 to 285 FPS. Pretty minimal change over 11k feet. Also pretty difficult to shoot 1 to 1.5" high at 40 and see it in your groups. I only shoot broad heads out of my hunting bow, so if I shot every arrow out of 10 a little high, I may look at adjusting, but what if I shoot one or two low. With enough arrows, I could see a 1 to 1.5" high pattern, but it would take me more than a couple strings of shooting to be comfortable enough to move my sight. And 1 to 1.5" at 40 yards is about 1 to 1.5 yards in distance. So the difference of shooting 40 or 41 to 41.5 yards, fairly small.

That is another reason to check your point of impact at medium to long yardages. There is no difference between 20 and 22 yards with my bow and probably most modern bows, so just checking your 20 may not show any difference.

 

[OR Archer]

I live at about 450ft. When I traveled to Colorado this past season and checked my sights at the trailhead(11,500ft) I was still dead on out to 50yrds consistently. Is this the norm? I don't know but it's just a good idea to always check it when you get to your destination. Leave nothing to chance!

 

[RosinBag]

OR Archer, I think more of the norm. I am in the same boat, but I agree people should check.

 

[Jared Bloomgren]

I turn my poundage down slightly in the high country to adjust for the change in arrow flight rather then changing my sights. At lower elevation I just crank it back up. Simple fix. With a significant gain in elevation the density of the air lessens. By reducing the draw weight, the arrow velocity remains the same which, in turn, keeps the point of impact the same. It only takes about a quarter turn, not enough to affect retuning my bow.

I shoot at the trailhead before packing in at distances out to 70 yards or as far as I can to check this. It has worked well for me.

 

[dotman]

I would say we all agree on always checking your bow over and shooting it when you arrive at your destination. I only shoot broad heads and shoot them year round, I have a very consistent group with a loose cannon everyonce in awhile. Every time i'm out in CO I have to adjust, I'm out there 2 or 3 times a year not always hunting but always with the bow.

 

[dotman]

Great idea Jared, I'll be in CO in a few weeks scouting/seeing family so i'll try that out.

 

[Ozz08]

Interesting stuff. I live and shoot my bow at around 300 ft. Last year before leaving the trail head at 9500ft. I shot groups from 20-60 yards as I was concerned with the elevation change and had absolutely no difference in point of impact.

 

[BuckSnort]

Roy, I believe you're thesis is flawed.. Please send me GPS coordinates to the trail head you mentioned so I can find the problem.. lol