Thread: Variables affecting precision

Prompted by discussion on another thread, I got to pondering if there was a way to visually represent the primary variables we typically play with when it comes to reloading and precision. After input from a couple of members, I updated my first attempt and have posted below.

It's not intended as a flow-chart or 'how to' of reloading, but at least suggests where you might get the best 'bang for your buck' when trying to increase precision. I also acknowledge that there will be different perspectives on the relative importance of different variables, however I've based my thoughts on my understanding of the data coming out of large sample testing discussed by Hornady/Litz et.al.

More than happy to be corrected here - I just like diagrams to help me understand concepts, and maybe someone else will find it useful.

having done target shooting and trained a lot of new shooters its flinching- positioning -relaxing - timing and trigger control get that right first before looking at much else - useless having a rifle that shoots half inch at 100 only to have a muppet on driving end thats shutting their eyes to shoot - I watched one shooter who turned their head away on firing

Originally Posted by Barry the hunter

having done target shooting and trained a lot of new shooters its flinching- positioning -relaxing - timing and trigger control get that right first before looking at much else - useless having a rifle that shoots half inch at 100 only to have a muppet on driving end thats shutting their eyes to shoot - I watched one shooter who turned their head away on firing

Yes - good example. I tried to capture that with the circle around all the other bits - precision can't be any better than the capability of the shooter, and arguably is the area where one might see the most improvement.

Years ago I read a very interesting article where the authors started with a sample of Remington Model 700s IIRC.

They went through and validated the grouping on each one. Then they carried out specific upgrades on each one and re tested group sizes post upgrade.

From memory, the two most dramatic improvements were the trigger upgrade and polishing the barrel. I read it in a magazine in a hut I think, and haven’t been able to find it online.

Your diagram is a similar principle. I don’t know if it’s dimensions and weightings or listed factors could ever be perfect as these will vary from shooter to shooter and also from rifle to rifle, but it is an excellent visual for how to think about the factors affecting accuracy.

I think charge weight and seating depth should be swapped based on Hornady data. Apparently dispersion improvement does correlate with lower (larger increment) powder charge changes. They did recommend trying a larger incremental powder reduction prior to changing bullet or powder.

Originally Posted by McNotty

I think charge weight and seating depth should be swapped based on Hornady data. Apparently dispersion improvement does correlate with lower (larger increment) powder charge changes. They did recommend trying a larger incremental powder reduction prior to changing bullet or powder.

That's interesting. I originally had those factors clumped together (and then separated them out) which may have kept things simpler. I guess the important takeaway is that the big 'levers' to pull, aren't necessarily the ones we have been told about (e.g. small powder/seating depth changes, chasing 'nodes' etc).

As an aside, I haven't seen much in the way of research about what measurable improvement in precision can be achieved through simply more practice at the range!

practice at range I find now can only do do so much and then concentration goes and shooting falls off rapidly- at that stage I stop- could be age I guess - worse with bigger calibres 22 good for 50 rounds until I start to fall of accuracy

(We can still use the word accuracy people, it still means the same thing it always did; you don't have to say precision if you don't want to...)

Good graphic. And I would say 'charge weight' is the same thing as where you have 'powder and projectile combination' (If what you intended was the choice of powder and burn rate, than you could say that is covered by charge weight anyway I think)

Here's a good one...



9mm at 50m (it's not a precision rifle by any stretch of the imagination). Top is 20 rounds of one bullet. Bottom/left is 6 rounds of a different one.

Go with bottom left 6 rounds, give the buggers a sporting chance

This is a very good approach. My suggestion would be to only accept changes where these are backed up by real science based, opinions, even those of "experts" don't cut it!

In the bottom section, assuming the bedding is fine, trigger comes after barrel in terms of contribution to both precision and accuracy.
And to JD point, I always thought they are quite different, in measurement at least, precision relating to the ability to produce a small group and accuracy relating to the ability to hit a particular aiming mark. (single shot).

Originally Posted by Tentman

This is a very good approach. My suggestion would be to only accept changes where these are backed up by real science based, opinions, even those of "experts" don't cut it!

Lol I have to laugh at the above, what is "science based" "who determines the science is valid" and what if the science is produced by someone who hasn't got a clue, they just group the information they have to back up what they want people to believe and eliminate the collected data that doesn't lead to what they want you to think.

I think the firearm part of this accuracy equation is a separate issue, as in separate to the ammuntion factors. overall precision shooting (the ability to deliver a projectile to the intended target, or the ability to delivery multiple projectiles to the same given point) can be broken down into.
1: External influences, such as wind, mirage, etc
2: Shooter ability
3: The firearms accuracy potential
4: The ammunition
In the diagram above the firearm and the ammunition are lumped together. Would it not be better to take the delivery system, the firearm, out of this and treat it separately.

Originally Posted by zeropak

I think the firearm part of this accuracy equation is a separate issue, as in separate to the ammuntion factors. overall precision shooting (the ability to deliver a projectile to the intended target, or the ability to delivery multiple projectiles to the same given point) can be broken down into.
1: External influences, such as wind, mirage, etc
2: Shooter ability
3: The firearms accuracy potential
4: The ammunition
In the diagram above the firearm and the ammunition are lumped together. Would it not be better to take the delivery system, the firearm, out of this and treat it separately.

Yes good points. I probably could have labeled it better. I was thinking more about reloading specifically, i.e. those things that we tend to play with, rather than all factors affecting precision.

I used the circle (shooter related factors) to lump a lot of stuff together, which I guess could include environmentals. I wanted to try show how any of the variables on the pyramid will be constrained by this. I guess if i was going to make a flow chart, I might say something like - step 1 - "establish baseline accuracy of platform and shooter", before progressing to playing with any reloading stuff.