Inconsistent groups

[49ereric]

Its not heat. The rifle has a heavy barrel contour and I let the barrel cool between shot strings.

I dont think its the scope or rings. I have the same set up on a different rifle and its shooting half moa groups consistently.

Is it possible to have that good of numbers but just have bad results on paper?

This same rifle and scope set up has shot sub moa groups with a different load. But I changed bullets because I didn't like the terminal performance. Now I thought I had a great load because it was grouping good at first and the numbers are awesome but the inconsistencies are killing me. At the same time it might be fine because the cold bore shots are in the same place everyday and within 5 fps of each other. On a hunting rifle thats really what matters.

Must be shooting ok with the cold bore shot doing well and that is all that matters hunting.

 

[EdP]

Is it possible to have that good of numbers but just have bad results on paper?

Yes, it certainly is, but that's not what you described. You said you get good groups one time and bad groups another. Apparently with the same POI since your cold bore shots are going to the same place. That suggests it is NOT a scope, mounting, or action screw issue as they would all cause the POI to change. I realize you checked these and concluded they were not the issue. I'm just pointing out that your results confirm your conclusion.

What does your sd and es look like if you combine good and bad group data so that you have 20 data points?

 

[tom338]

How many times have you reloaded the brass?? Do you anneal it?? Might be neck tension is different between pieces of brass. When you resize is the should bump consistent from piece to piece of brass. I found that most of my brass was very inconsistent. Started to anneal and a lot of issues started to disappear

 

[Vern400]

I've got a really picky rifle that I can't figure out, my groups from the same load on different days are sometimes sub moa and other days around 2 moa. The SD and ES is always really good though. Like 6 fps sd and under 15 extreme spread. Its not shooter error because I am shooting another rifle and printing sub .5 moa groups on the same session.

Its making me think there is something wrong in my handloading process. And I dont understand how the numbers are so good but the groups open up

Three and even five shot groups can prove you're bad. But they CANNOT prove you're good. I don't know how many YouTube videos I've seen where people say, "OH that's just a flyer. I musta pulled it". Don't be that guy.

To you, does a 1 MOA rifle shoot moa if you printed a single 5 shot group 0.8 inches and a bunch of bigger groups?

I worked many years with reliability engineers and found going from 50% confidence to 80% confidence of test success required about twice the precision. The work was in a manufacturing environment with many variables, just like handholding. They are two different things, true. But the mathematics and statistics of hitting a goal is essentially identical.

So if I wanted to be pretty confident that I had a one MOA rifle, I'd have to shoot a lot of groups that were under half inch. I would rarely get a 1-in group under good conditions.

Right now your sample size doesn't allow you to really identify a problem. Sling out a few 10 shot groups, and call no flyers. 30 samples is what most statistics guys would consider the least they would give an opinion on.

Then, if you have 30 samples below 1 MOA, and later on you shoot a three shot group that is three MOA you'll know for sure something changed. For me, that happens EVERY time I clean my 308 barrel. It takes three to five shots to come back in. I've shot lots of 0.4's and 0.6s. 5 shots. But occasionally I'll bust out a 0.98. It's a 1 MOA gun as best I can tell. If somebody bets me a $20 bill on a clay pigeon at 300 yd I have an excellent chance of taking his money. Sadly my eyes aren't 30 or 40 years old any more and some days I'm not a 1 MOA shooter.

Hornady has a couple of very good podcasts on group sizes on YouTube. They're a good watch. And I hope you'll be able to narrow down your issue and get confidence in your system. Unless you're shooting F class, confidence matters more than a sub MOA gun.