Deception of 100 yard Groups - appreciate some wisdom

[frankinaustin]

Howdy everyone - so I'm new to hand loading. Over that past 3 months I had developed about 6 or so "good enough" loads for my 7mm-08. ("Good enough = less than .8 MOA at 100 yards in a 3 shot group.). However, I went to a 300 yard test and determined that in fact only 2 of my loads actually shoot under MOA at 300 yrds in a 10 shot group. My ask us this: what gives? Why doe a sweet 3 shot sub MOA load at 100 turn into a 3+ MOa group at 300? What truth have I discovered ? Any wisdom would be very much appreciated.

((Btw the 2 loads that I have that shoot sub MOA at 300, I now have a whole lot more confidence in...))

 

[EddieHarren]

3 shots vs 10 shots? Think about it. Shoot 10 shot groups at 100 and then 10 shot groups at 300.

 

[MudRunner2005]

3 shots vs 10 shots? Think about it. Shoot 10 shot groups at 100 and then 10 shot groups at 300.

Bingo! Why would you shoot 3-shot groups at 100, then 10-shot groups at 300?

 

[gohring3006]

Eddie and mudd are right 10 shots will heat any barrel up but you said you had two of your loads shoot sub moa 10 shots they are in that sweet spot in your load and barrel combo the one load that shot great at 100 then fell apart at longer range is close to the sweet spot but not quite, its barrel vibration, harmonics more than likely I would scratch that load and use the other two

 

[Rick Richard]

I can't explain it, but I no longer shoot at 100 yards to determine load accuracy. I now shoot no less than 200 yards and much prefer longer. Like you said, longer distances that exhibit excellent accuracy builds confidence.

 

[cowboy]

I can't explain it, but I no longer shoot at 100 yards to determine load accuracy. I now shoot no less than 200 yards and much prefer longer. Like you said, longer distances that exhibit excellent accuracy builds confidence.

Agree with the above. I see no reason to shoot at 100 yds to test for accuracy on a LR rifle. I don't have a rifle, other than my small varmint rifles, that I could tell you what they shoot at 100 yds. I test my loads at a minimum of what I want that rifle zeroed at - which is mainly 200 yds.