Me and a buddy of mine were talking and he asked how come I always shoot at 100 yards to determine a load for rifle and I told him I had always done it this way and he asked why not 200 or 300yrds and I could not give him a answer other than I had always done it this way, so I got to thinking and now I am wondering why not ? does it need to be at 100 ?

If 100 yards gives you group sizes where you can readily tell the difference between loads then 100 is fine. If not, move farther out. That's always been my practice...

I have always set up multiple targets and shot say 43.5 on one 44.0 on another and so on but can you do the same at say 200 yrds instead of 100 ?

1. At 100 yds, 1 inch POI shift equals approx. 1 minute of arc.
2. Beyond 100 yds, I start skipping into my neighbors yard (already had to replace one propane tank and a cat)
3. The europeans started it by shooting 100 meters.
4. Just a convenient reference distance.

200 can be better because it gives the bullet more time to settle down (not all loads benefit).

I usually do my testing at 100, because I can see the .224 holes at 100.  They're a lot harder to see at 200 or 300.  .30 cal holes I can see at 200 or sometimes at 300.

1
You sure that was a skip?
'Borg

Plus one on the "see the holes" issue.  At 200-300 yards you often need a spotting scope to see .223 holes depending on the optics you have on the rifle.

You can argue the "time for the bullet to settle down" issue eoither way, but if it has to settle at all you need to consider your rifling versus bullet weight/lenght.   More practically speaking, a light fish tail wind at 100 yards is not going to have a significant impact while a light fishtail wind at 200-300 yards will introduce far more variation than you ever gain from having more distnace for the bullet to "settle down". The same thing is true with a steady cross wind - the longer the range the more variability will be introduced by changes in wind speed and direction.

That leaves 100 yards as more or less the sweet spot for getting a realistic picture of how the round will perform at enough rnage to begine to show dispersion patterns while still being close enough to easily see the holes and not causing issues with the wind or severly limiting the days you can shoot for minimum group size and have the difference be due solely to the load.

So I do my load development at 100 yards.  In really calm conditions, it does make sense to shoot at 200, 300 yards and beyond to confirm how a load and you rifle really perform, but those days are a bit too rare to devote to load development.

There's also the factor of your shooting distances.  Some bullets perform very well at 100 yards and not well at all at 1000,
and vice versa.  If your primary shooting is going to be hunting at 100-200 yards then it makes sense to do your load development
there.  If you are going to be shooting 600-1000 yards then it makes sense to do your load development at 200 yards or greater
due to the factors other posters have mentioned.

Thanks for the info, I will stay at 100

For 223, I used to do everything at 100.....until I decided to shoot 300 !
Freaky stuff started happening and I realized I wasn't the "sharp-shooter" legend in my own mind !!!!

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Find a sheet of poly shipping foam, make a frame and hang it approx a 30 degree angle behind the target. It will reflect light back at you through the bullet hole in the target, and it is pretty much self sealing after the bullet goes through.

Linky
Try and find it locally, the above link is to show you the type of foam I'm talking about.

It is most often not the bullet that shoots proportionately better or worse at greater distances,but rather the rifle.  For example, the Lee Enfield Mk III was famous for shooting better groups at 1000 yards due to some peculiar barrel/rifle harmonics,

Checking the standard deviations of your loads will tell you a lot about the potential long range performance.  A load with a stnadard deviation of 15 fps will give you an extreme spread of velocity of about 45 fps.   In contrast you may also have a load that shoots exceptionally accurate groups at 100 yards, but has an SD of 50 fps.  A load like that will give an extreme spread of 150 fps and that will show up in greater vertical dispersion at longer ranges, and with any wind at all, will create more horizontal dispersion as well.

Conseqently, if shooting at long range, you will probably be better with a slightly less accurate load that has more consistent velocity than you are with one with a high SD but great short range accuracy.   In general loolking at the SD tends to take out most of the surprises when shooting at longer ranges.  

Where bullet issues come into play is usually a mismatch of the barrel and rifling. Using the right barrel twist and or the right weight bullet for your barrel twist tends to ensure consitency  at longer ranges.   The old argument is whether 55 gr shoots well in a 1-7 twist barrel.  It depends on how the quality of the bullets, how picky you are in terms of accuracy, how high the velocity happens to be,  and how far you are shooting, but in general bullets that are over stabilized tend to yaw and fly what amounts to barrel rolls through the air for a distance before they settle down.  

The yaw and precession effects from less than perfect bullets spun at excessive rpms increase dispersion slightly over short ranges but greatly increase dispersion over longer ranges as they don't consistently settle down pointing in identical directions with identical vecotors, so accuracy is much worse than expected at long ranges.  Bullets that are understabilized tend to yaw toward the end of their flight paths, so they may also shoot well at short range, but have poor accuracy at long range.

Sir, first I'll qualify my response by mentioning that for rifle loads I intend to use in competition I do all my load development testing at 200yd.  The range I use has overhead concrete baffles and is fairly well enclosed minimizing the effects of wind.  I chronograph all my loads as I shoot for groups and have found that it's easier to see the beginnings of shot dispersion at 200yd and combined with the chronograph data it becomes quite easy to pick out the best loads with SD and ES data immediately at hand.  With my Kowa scope it's generally possible to see shot holes in the aiming black given adequate ambient lighting but a reflective background behind the target is helpful as already mentioned.  I use nothing but SRC targets at 200yds as that's the shortest distance I normally shoot in competition.  Given a low SD and ES it's fairly easy to determine which will be the best at longer distances.  Generally speaking at longer distances wind conditions become more of a factor so it's only seldom that I do any testing at those distances.  HTH, 7zero1.