1000 yard problems.

[shortpants]

I thought that was a good explanation except that if it were me I would take the 1/4" group load and the 5/8" load and test them again at long range to see if what you think is going to happen in theory actually does. I'm a believe it when I see it and stubborn sob.

 

[270winshort]

I thought that was a good explanation except that if it were me I would take the 1/4" group load and the 5/8" load and test them again at long range to see if what you think is going to happen in theory actually does. I'm a believe it when I see it and stubborn sob.

Thanks for the complement , I would agree that I would also want to go test and confirm at long range in the past I have had this situation come up and the load that shot a bigger group at 100 yrds actually shot better groups from 300 yrds on out, I have had this happen on several rifles, but I would agree the tighter group may work just fine, it is always good to go shoot and verify what will work the best

 

[bowhunthard88]

I would also agree with the heat issue, but I am also wondering how well does it shoot at a 100 yrds,and what kind of numbers are you getting out of your load, S.D. if your S.D. is not in the single digits this could also be part of your problem as well, if your 100 yard group throughs one low once in a while you could also have a load issue.I have a factory model 70 win that is a feather light and it will hold 1/2 moa at a 1000 shooting a 5 shot string then it needs to cool back down,

SD and ES could be a part of the issue, but should not affect the group consistently (unless velocity is changing that much as the barrel heats)... Also noted in a different post, cryo treating, I personally wouldn't recommend cryo treating unless your rifle has be been trued completely. You'd want to make sure all stress, such as it is, is as consistent as possible. If that makes any sense.

No offense meant to the ones that posted these.

 

[bigngreen]

When I first started shooting at a grand with my 270 WSM it would walk down a couple MOA also, it came to be two issues, the first was me and my shooting. I was holding and forcing the rifle then as I relaxed the shots ran down hill, the second issue was resolved by facing the action and installing a square recoil lug and truing the barrel nut (Savage) thus relieving the source of stress.

 

[Lancet]

Shot it at 1000 yesterday, lettin it cool done between shots and I didn't have an issue with it!!! Thanks guys!!

 

[Eaglet]

Extreme Velocity Spread and SD have always made me space out...

In the user's manual for the CED M2 chronograph, they say the following:

statistically, it has been proven that 68% of all things measured will fall between one
standard deviation above or below the average. Additionally, 95.4% will fall between two standard
deviations above or below, and 99.7% will fall between three standard deviations above or below the
average.

Let's look at an example.

2995 fps
3005 fps
2994 fps
3002 fps
3003 fps

Average = 3000 fps
Spread = 9 fps
SD = 5

Just about all would agree that's a pretty good load!

Let's say we shoot the rifle many times and over all it shoots with the above mentioned consistency.

Now, by definition,
68% of the shots would fall between 2995 fps and 3005 fps.
95.4% of shots fired would fall between 2990 and 3010 fps.
99.7% of shots would fall between 2985 and 3015 fps.

This would also mean that if we shoot a group of 10 shots and we know for a fact that our load has a SD=5 then:

About 6.8 shots would have a velocity between 2995 fps and 3005 fps.
9.5 shots would fall between 2990 and 3010 fps.
9.97 shots would fall between 2985 and 3015 fps.

This insures me that from my average velocity all shots would be somewhere between ±15 fps.

Bottom line, if I'm shooting my 300 RUM light load using 210 gr. Berger at 3000 fps muzzle velocity, when my mv=3015 it'd be 2.0" high and when mv=2985 fps it'd be 3.0" low.

My conclusion is that if we want to shoot ½ MOA at a 1000 yd, we'd need our load to be in the single digits for ES and SD.

What do you guys think?

 

[Lancet]

What does ES and SD stand for? That's where you lose me.

 

[bowhunthard88]

What does ES and SD stand for? That's where you lose me.

ES = extreme spread between velocities, and SD = the standard deviation of said velocity.

 

[Eaglet]

What does ES and SD stand for? That's where you lose me.

Lancet,

ES stands for Extreme Spread (speaking of the velocities)

Example:

2995 fps
3005 fps
2994 fps
3002 fps
3003 fps

The difference between the highest number and the lowest number is 9 fps
so your ES = 9 fps

The SD is a bit more complicated but it stands for "Standard Deviation".

In statistics and probability theory, standard deviation shows how much variation or "dispersion" exists from the average.

So in our example above, the average is 3000 fps, (The sum of all five values divided by 5)

Average = 3000 fps
ES = 9 fps
SD = 5 fps

I hope that helps.