"mid-range" loads and accuracy?

[hardheart]

I'm trying to wrap my head around the statement I've seen in several places that 'mid-range' loads tend to be more accurate. What does this mean? Is it powder specific? Does it apply to only certain burn rates? Has it got something to do with what the max pressure is? Are some cartridges inherently more accurate than others because they have a lower case capacity? Is it something to do with the way the powder burns, or is it just reducing recoil? What I am wondering is what is the difference between a max load and a mid-range load if we were to compare

40 vs 10mm
9x18, 9x19, 9x19 +P, 9x23
357 Sig vs 9x25 Dillon
45 vs 460
45 Colt, Ruger only, 454 Casull
38, 357 magnum, 357 maximum
44 SPL vs 44 magnum

In the instances with the exact same bullet and the same powder with a different charge weight, what effect does a mid-range load have when that is mid-range to a 20K psi max, or a 35K psi max? And how has the change in SAAMI max pressures and the creation of +P affected accuracy? Are SAAMI compliant charges more accurate than CIP? When reloading manuals vary by a full grain in staring and/or max loads for a powder, is there more than one accuracy locus?

 

[NWcityguy2]

That idea goes hand in hand with the other ideas like max load should be avoided, perhaps used only occasionally or only by an experienced reloader. If you experiment enough you will find one load weight of powder that is better than another load weight, I'm not disagreeing with that. However max loads changes over the years, changes from manual to manual and if the masses actually had pressure testing equipment would change from gun to gun.

Simply put there is no unofficial rule that just below max load you will find the best accuracy.

 

[918v]

I'm trying to wrap my head around the statement I've seen in several places that 'mid-range' loads tend to be more accurate.

That is an inaccurate blanket statement.

 

[rcmodel]

What is closer to the truth is, mid-range loads can be shot more accurately by the shooter.
Any shooter.

It is easy to concentrate on good shooting basics when your brain isn't telling your eyes to get out of the way.
Cause there is about to be a large explosion go off right in front your face.
Just as soon as your finger gets through giving the trigger a jerk.
And the rest of your body flinches!

All Bullseye target shooter know this.
Thats why they all shoot Mid-Range match .38's & .45's and not .357 & .44 Magnums.

rc

 

[ConcernedCitizen]

I'm not sure if this applies to handgun cartridges, but I believe it may have something to do with barrel harmonics.

The way I understand it, accuracy is almost a sine wave. Groups will shrink, open up, and shrink again as you go up the ladder. Most people find their accuracy node with a low to mid-range load, and stop there. I've also talked to reloaders that have found an accuracy node at or slightly above max.

My theory is that there will be multiple accuracy nodes for a firearm, but you might not always be able to find the one at the higher end of the range before the firearm tells you it's already at maximum.

I'm a firm believer that less wear and tear is a better thing, and most targets can't tell the difference between a mid-range load and one that goes 100 fps faster.

I think rcmodel also has a good point that some of it might be psychological, not just physical. I personally enjoy shooting my mid-range competition loads much more than shooting my +P home defense loads. I know the +P is a better defensive load, but I'm much more confident in my target loads to hit exactly where I'm aiming.

 

[fecmech]

RC pretty much nailed it, mid range is more for shooter comfort. Accuracy is where you find it. When I shot Metallic Silhouette my .357 magnum and .44 mag full power loads were more accurate than factory .38 wadcutter match loads. That said I would not want to shoot timed or rapid fire bullseye with my silhouette loads! You don't need to hit paper that hard!