cherokee_outfitters

What happens to a hunters rifle and load when he leaves 1000ft elevation and travels to 10000 feet on a deer or elk hunt? Well after playing with this for years I've learned there is major effects on bullets and loads from lower elevation to higher elevations. Here is just an example of what happens to a mediocre factory load in the high country.

30-06 165gr Interbond load: 10,000 ft elevation

yards velocity energy ftlbs drop
0 2900 3081 -1.50
100 2747 2765 1.56
200 2600 2477 0.00
300 2457 2212 -6.65
400 2319 1970 -19.06
500 2185 1750 -38.69

30-06 165gr Interbond load: 1000 ft elevation

yards velocity energy ftlbs drop
0 2900 3081 -1.50
100 2691 2654 1.66
200 2492 2276 0.00
300 2302 1941 -7.21
400 2120 1646 -21.12
500 1945 1386 -42.53

Now being these are the same exact loads at different elevations you can see alot of change in all three factors between the two loads. You can expect a higher level of preformance from the same load at higher elevations say a elk hunt at 10,000 ft or more. Given this information some substandard elk and deer calibers become more than adequate in retained energy at longer ranges. This is just information that most hunting magazine writers over look when they talk about preformance in calibers adequate for medium size game. Of course you have to be hunting around the 10,000 elevation to obtain these bonuses to your calibers.

Check out the difference between a 30-06 165gr interbond at 10,000 ft and a 300 win mag 165gr interbond at 1000ft elevation. I think you will be amazed at the results when the bullet reaches the 400 and 500yd mark. 300yds being the leveling off point of the two where they come close to the same three factors.

300win mag 165gr interbond: 1000ft

yards velocity energy ftlbs drop
0 3100 3521 -1.50
100 2895 3071 1.34
200 2700 2670 0.00
300 2512 2312 -6.08
400 2333 1993 -17.65
500 2161 1710 -35.76

Now beings the 30-06 was shot at 10,000ft and the 300winmag at 1000ft of elevation is seems not a fair comparison. Shooting the 300winmag at 10,000ft will have tremendous gains in all three factors. But that's not the point. Using a standard factory load from a 30-06 at 10,000ft elevation gives you a 300winmag preformance out of a non-belted cartridge. Which gives the hunter an added bonus on their deer or elk hunt at higher elevations. You can research this information for any elevation your hunting at. With this data it pushes the envelope of a standard 30-06 factory load to a higher level of range and retained energy while hunting at the higher elevations. Same results with all calibers in the starting class of elk calibers like 270,280, and 7mm mag. Loads like my 300win mag handload and ultramag loads are absolutely amazing compared to what you will find in the back of a hornady reloading manuel. Truly optimizing the calibers potiential to the max.

In the past hunting at lower elevations brought about my curiosity on bullet drop vs. higher elevations. Taking my rifle to lower elevations of 4000ft and lower the bullet would drop 2 to 3 inches lower than my 200 zero from the higher elevation. So years of curiosity brought on the research of elevation effect on bullets.

So is it necessary to check your zero when hunting at different elevations.(YOU BETTER BELIEVE IT) !!!!!!!!

justhuntitall

You are so right I live in IL where the elev. is around 500' to 600' and when we hit elev out west from 9000' to 12000' you are always shooting hire. I shoot a 270 win. 150 gran bullet and its alittle better then an inch at a hundred yards so we spend are first hour after we get camp up to check our rifles.

Also the hire elev. makes a diffrence on are bow equipment seems like we always shoot a touch hire .

James B

Good information. Thanks for going to the work posting it. I have noticed this difference even where less difference in elavation is concerned. Where I live we are at 1400 feet ASL. Where I hunt is from 3500-7000 ft elevation. I always fire a shot or to before the hunt when I get to my hunting destination just to be sure. I don't often hunt above 7000 feet anymore. I used to a lot though.

txhunter58

I can't think of anything that would make such a difference except thinner air (less resistence or drag on the bullet), which results in higher retained velocities.

Just out of curiosity, how did you come up with those velocity/energy figures? How would you chronograph the bullet at 300 yards?

James B

There are some good ballistic programs that can give you all the info you need. I think Sierra makes one of the better ones. I have seen it advertised in Rifle magazine and Rick Jameson uses it quite often in his writings.

cherokee_outfitters

txhunter58,

It is the factor of less air density and humidity that make up the factors in which make the bullet retain velocity which produces ft lbs of energy and the trajectory flatter. Theres also barometric pressure change factors. Which goes something like this 1" of change of barometric pressure equals somewhere around a 1000ft of elevation change. Also there's the hot and cold factors. But just for the sake of the rest of the readers of the column I won't bother describing those. You can find all that out through research.

I have several computer ballistics programs. Tons of reloading manuals. And many days at the range testing out stupid crap just because I read about it somewhere. lol Most of it you can through out the window. But not checking your zero when changing serious elevation could be a major factor on a longer shot.

I do chronograph at 300yds using a 1" steel plate cut out to shoot through that has a 6" hole in it. I also use 1/8 dowel rods inplace of the metal ones for the just in case opp's. I also shoot for groups upto 500yds every year no matter how many times I've loaded the same load or shot the same rifle I like to know exactly where the rifle shoots before taking off on my hunts.

PLB

Excellent post cherokee,

it is always best to check your zero at the altitude and temperature that you will be hunting.

As a rule that will get you close, for every 2000 feet in elevation that you go up, your bullet impact will be approximately 1 MOA high and it just the oposite for drops in elevation.

There is another rule for tempurature, if my memory is correct, for every 10 degrees drop in temp, your bullet impact will be 1 MOA low.

Among other things the air density/drag on the bullet causes the change in zero.

(those rules apply to the .308 win, I never used them/tested them on other caliburs, but I would guess it would be close)

CalNewbie

Thanks for the post, this is great information.

PLB - you raise a good point. I was amazed at how much my zero had changed between range trips. Early October trip, temp in the mid to upper 80's versus a January trip, temp in the low 60's. Same ammo, second half of the same box in fact, were several inches off. At first I thought my scope had been jostled, but the shots were "zeroed" horizontally, but were off vertically. Later, I thought about the temperature difference but wasn't aware that it would make such a difference in the point of impact.

remsal

If you get a program on CD-ROM Sierra bullets, you can plug in all kinds of different scenarios. One thing I noticed while planning a deer hunt to Canada last year was that an decrease in air density due to elevation increase is usually almost cancelled out exactly by the increase in density cause by decreasing temperature. I was comparing a sight-in at 100 MSL (mean sea level) at 80 degrees F to my expected hunting situation of 2000 ' MSL -10 F in Canada. The differences in the trajectories the program gave me wer negligible. Unfortunately, once I got to Canada and checked my rifle, it became apparent that my gun had been severly knocked around somewhere in the security process, so, I did not get a good idea of exactly how close it actually was. In any case it is a good idea to always re-zero your weaopon once you have the opportunity in the environment and altitude you will be hunting.;

windriverhunter

Neat post, cherokee. Thats pretty interesting. I live in Wyoming at about 5000 feet, but less than an hour drive into elk counrty takes me up much higher. I never thought about my bullet performance changing in just an hour, but you post made me wonder if my zero really will be affected. Good research and cool post!