Obtaining more information from your groups - overlaying groups

Ok here's this morning effort.

First up I tried @Tentmans challenge... And failed on the last shot.

https://i.postimg.cc/5NwwzKXX/First-five-group.avif

I gave the rifle and myself a little time to rest from the heat and the walk, and fired another five shot for @gimp.

https://i.postimg.cc/zXmCVYGm/10shot-group.avif

There was a pattern. In both case the first 3 were in the intended 1MOA bull for the first group the first 4, and then the last 1 or 2 shots from each were out too left.

Any explanations?

Next I did a very rough sight in of the 280AI with the ammo I had remaining, which was 3 rounds of 150gr LRAB. Which I used to get on the paper. Ive marked them with a line through the two that can be seen.

And then I used the 8 160gr Accubonds I had to shoot a group for gimp. To be honest Im not sure if any info can be gained from this. These are the first shots fired from this rifle in 3 years so the first 4 grouped left and from past experience its a reasonable group for this gun. But on reloading the mag and firing the second 4, they made a complete seperate group too the right? No adjustment made by me.

https://i.postimg.cc/8zNLmdvt/280.avif

@ANTSMAN @Tentman Here's the latest version.

https://filebin.net/jl76ne6g2ypd3q3g

Quote:

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Originally Posted by whanahuia

Ok here's this morning effort.

First up I tried @Tentmans challenge... And failed on the last shot.

https://i.postimg.cc/5NwwzKXX/First-five-group.avif

I gave the rifle and myself a little time to rest from the heat and the walk, and fired another five shot for @gimp.

https://i.postimg.cc/zXmCVYGm/10shot-group.avif

There was a pattern. In both case the first 3 were in the intended 1MOA bull for the first group the first 4, and then the last 1 or 2 shots from each were out too left.

Any explanations?

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To me it's just the random variation you get in groups - more shots is just filling it out. There is the possibility that you have a bad barrel and it does warp with the heat from 3 shots, I have never actually seen one that does. The only way to test that is to fire a lot of cold bore shots and see if they do anything different vs a few fired at the same time. A handful of shots really isn't enough to robustly understand a trend, it is very easy to falsely ascribe a trend to a few shots - but you can easily get even 10 that happen to fall to one portion of the true cone of fire just by chance.

Quote:

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Next I did a very rough sight in of the 280AI with the ammo I had remaining, which was 3 rounds of 150gr LRAB. Which I used to get on the paper. Ive marked them with a line through the two that can be seen.

And then I used the 8 160gr Accubonds I had to shoot a group for gimp. To be honest Im not sure if any info can be gained from this. These are the first shots fired from this rifle in 3 years so the first 4 grouped left and from past experience its a reasonable group for this gun. But on reloading the mag and firing the second 4, they made a complete seperate group too the right? No adjustment made by me.

https://i.postimg.cc/8zNLmdvt/280.avif

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It's hard to say here, either it's a really imprecise rifle and the "split group" is just what you happened to get - this happens sometimes, you just pull out random bits of the cone that look weird, even with 10rd groups - e.g. this is a group from a rifle that usually shoots a reasonably round group but this time it just threw a weird distribution - mean radius and group size are normal enough but it looks weird

Attachment 268694

OR it's got a broken scope, poor bedding, loose mounts, etc and the actual POI is changing. Not enough information to say but it's worth checking all those things.

The group circled in red is the group above vs all the other 10rd groups I have on file for that rifle - it's very much in line with what that rifle does as far as representative extreme spread and mean radius, but just ended up a weird shape.

Attachment 268696

I'll do it again in a couple of weeks. There is another option too. I didn't feel particularly comfortable in my Shooting and controlling my heart rate today. It could well have just been me as well.

Your 10shot group from the
.270 looks about as good as you can expect from any good hunting rifle, so there's little to be concerned about there with regards to shooter error I think. 0.43 inch at 100Y (assumptions) means about 0.12MRAD mean radius. That's on the better end.

Attachment 268700


Slightly difficult to see where your actual impacts are

You got it pretty close. 9 is a bit further out more in line between 7 and 8 and the 10 is where the circles of the white x and red x intersect.

Is the small white x the true centre? With an MRAD scope one click right would over adjust by a similar amount I think?

Yes the white X is the true centre - It's not quite clear that the image is totally square with the top circle directly above your black dot, so the alignment of the zero might be a little off 1 way or the other 1 - but it looks like it's within 1 click at this stage


at 100Y a 0.1MRAD scope click is 9.1mm; a 0.25MOA click is about 6.6mm
At 100m it is 10mm and 7.3mm

shit it's a lot of juggling going between units - let's just go 100% metric

Yeah. I actually shot that group at 100m because I feel it makes things easier with my scope with adjustments being 1cm per click. And will end up doing my entire range in meters I think.

Just bear in mind Part 6 of the Act

It's an area you sometimes use for private sighting in .... not a range ....

Yep.Thanks. But frustrating that we have to clarify that.

Here's my go. Tikka Strata 243 1/8twist , Targex 95g projs x 10 shots with small Burris 2-7 scope. I actually thought the group would be bigger than this , cos I had had enough and sorta didn't take the time I would normally take.
Had a mare before this, with as yet unexplained phenomena.

I've got to get it suppressed, cos muzzle brake on a 243 is stupid and very LOUD, and then Ill shoot another 2 x 10 shot strings and overlay them.

Attachment 268742

Attachment 268745

A test to see if I've got the Hornardy app Sussed. From my 223 with Sierra TMK 69s. Still getting this rifle sorted, it's up past 200 rounds but is bullet fussy. Wish it was like Gimps haha

4 words Foster - cut rifled match barrel

Outing to the range (proper range) 18” Tikka 300wsm shooting 168gr AMAX, Re17

Attachment 268812