Home Forums Hunting & Shooting Ask The Gunwriters Group shape, does it matter?

I know trying to read anything definite into the shape of a group is up there with reading Tea leaves and bone oracles, but what if they are consistently something other than round or triangular?

Is it significant if the group itself is reasonably small? Stringing usually indicates a bedding or scope problem but what else is revealed by the group shape?

On higher magnification scopes and light kicking or varmint guns, I can see on paper where my heart beat comes into play.

This topic is valuable and has never been covered by a writer to my knowledge. Group shape tells you everything, but you need a lot of bench time with super accurate rifles that have reliable and repeatble accuracy levels to learn this:

If the the groups are equilateral triangles in shape, the bullet needs to be seated out. I turn the seating die out a 1/4 turn and retry until the group closes.

If the group has 2 together and the 3rd out further, the bullets needs to be seated deeper by the same method. Bedding issues, loose action screws or scope mounts will generate erratic groups with no pattern to them.

The fly in the ointment with my comments is if you find you have to seat a bullet out, internal magazine length becomes a consideration and some compromise may have to be made for hunting loads.

That does not mean you canot put a few loads aside for single loading that are super accurate and over max length for your magazine box. For a shot or two at pronghorn on the plains, take advantage of the better load and OAL.

JW

AussieGunWriter
I've never heard that one before,I'll have to try it or use it for an excuse.
Of course stringing shots is often bad technique.I have no excuse,I'll just have to shoot more.

The book "Ultimate Rifle Accuracy" touched on the subject. But it is in the Deep Voodoo category so it makes it hard to come to any firm conclusions. I think most Hunting rifles don't even qualify for consideration.

I think another article could be written on the myth of the consistent quarter inch groups in hunting rifles, although plenty of varmint rifles could do it.

Hence my comments that this topic has never been covered by a writer before. It is not voodoo, it is a subject beyond the experience of most writers thats all. And, the very reason why writer's are generally not respected by the benchrest fraternity. Not a criticism, just a reality, as most writers tend to photograph a single best group for their articles and that will not represent the accuracy of the rifle tested.

You are also correct that 1/4 minute sporting rifles are generaly not common but they do exist, so it is not a myth, and obviously more common, is the half inch rifle depending on your criteria for accuracy. Most rifles will generate MOA performance out of the box with good ammo and a good rifleman which is the rarer of the two.


JW

I would add to AGW's comments (and he is a VERY good source of knowledge) that powder charge can cause both stringing up and down and sideways.

Also, if you're getting 2-3 shots close and one slightly out--especially consistently high left or right--and the barrel is free-floated, then the free-floating isn't enough. The barrel is probably touching the forend during some shots and not others. The fliers are coming from when the forend "taps" the barrel.

But there are a number of reasons for fliers. I recently tested a rifle that would consistently put the LAST four shots into less than 1/2" with any load, but the first shot was always slightly high. This was due to the scope. It was slightly loose internally and took one shot to settle down.

Some barrels will shift POI when heated up, even when of quite heavy contour.

In other words, there are a bunch of different "patterns" but it takes a whole lot of shooting to experience them--and I suspect that a lifetime isn't enough to experience all!

Which is the reason I have written some about this but will write some more....

It isn't Voodoo or magic dust. It is shooting thousands of rounds in a multitude of weather conditions and keeping meticulous records of what worked and what didn't for a give combination of barrel, bullet and powder. Then it's still a guessing game of which way to move the seating depth or change the powder weight to bring the rifle into tune. Just not something you can read in a book and be sucessful at.

Good call John. I thought about covering scopes but did not want to complicate the answer so am glad you covered it. The fact is you are dead right, scopes problems can play havock with grouping.

JW

You bet it does, it can tell you exactly why your gun is performing in the way that it does, if also tells you how to correct the situation. You show me a picture of your group with the holes number as they were shot and I can tell you how to correct it, if its in the bedding. It's as basic as Ned in the First Reader!

'Extreme Rifle Accuracy' by Mike Rattigan goes into quite a bit of detail on tuning loads and diagnosing groups for benchrest shooters. The thing with tuning loads once you get under the 1/2 moa @ 100 yds is that you have to be able to deduce whether it is the load that is causing irregularities or patterns in the group or wind, mirage, minute parallax problems, bedding, or gunhandling while shooting. To do this you have to have windflags and understand how to read what they are telling you or shoot in a tunnel. You also have to have a gun and components that are capable of the accuracy required to tune to these levels.

I guess my big question is when do you stop the load juggling and tinkering? I am thinking primarily of light to medium weight hunting rifles. A solid shooter for me is anything around an inch that is consistent, hot, cold, fouled, clean or any normal condition.

The rifle that is bugging me is doing around 3/4" but with erratic groups that I think can be better. I probably should be thrilled with it as it's a meat maker already.