Some load recipes perform well in the vast majority of rifles that are chambered for them.
I've wondered for quite some while now why certain recipes seem to shoot well in most every rifle they are tried in. The current Winchester Super-X Power Point 130 grain .270 factory load has yielded MOA results for every .270 I'm familiar with. If you own a .270 you should try this 11 dollar per box (Walmart price) factory load. It's unbelievable.
57.5 grains of H4350 with a 165 grain bullet does wonders in most 30-06's, as does 55 grains of IMR 4350 with a 130 grain bullet in most .270's. Another .270 recipe used by many, many shooters is the 60 grain charge of H4831 with the 130 grain bullet. For an excellent .308 varmint round, try the Nosler 125 grian Ballistic Tip with 51.5 grains of W748 behind it. I've not seen a decent .308 yet that wouldn't shoot this load MOA or better.
So the question is, why is this the case?
If we begin with a rifle that has no major mechanical flaws, such as poor bedding, bolt squaring problems, or just a plain bad barrel, we should expect it to shoot a proven load at least MOA. I'll grant that tweaking a known good load a bit (usually with bullet seating depth adjustments) normally does make the standard recipe perform even better.
When the bullet goes down the barrel, a couple of significant things happen. The entire barrel vibrates like a tuning fork, with the muzzle moving up, down, left and right in a predictable and repeatable pattern. Each barrel will have its own unique vibration pattern, which is affected by the size and shape of the barrel, the integrity of the steel, the bedding (or lack thereof) in the forearm, etc.
The main thing is that this harmonic whip be very repeatable. If the rifle has bedding issues, or other problems, this harmonic vibration will be erratic from one shot to the next, and accuracy--no matter how good the ammunition--will be unsatisfactory.
If we assume that there are no issues that affect shot to shot repeatability of the harmonic whip, then all we need to have an accurate rifle is a load recipe that can really perform consistently. So long as the load recipe has the correct amount and type of powder for the bullet it is pushing, each cartridge will perform in a repeatable manner.
Some load recipes are not consistent. Loads with low load density numbers (meaning that the powder doesn't fill the case to 85% or better) are often poor performers because consistent ignition can't be obtained. These loads will release the bullet at different points on the harmonic whip of the muzzle which of course ruins accuracy.
The ideal is for the bullet to be released when the muzzle is at a relatively stable portion of the harmonic whip, such as when it has slowed down just before changing directions. This creates a greater window of opportunity for the bullets to all be released at the same point in space, meaning they will hit the target in the same place.
Of course a given load recipe, such as "57.5 grains of H4350 with a 165 grain bullet in the 30-06" may release the bullets at an "opportune node" of the harmonic whip in one rifle, but not in the next rifle. No major matter. The above load recipe is consistent enough in and of itself to yield acceptable accuracy even when the bullet is being released during a particularly fast linear portion of the harmonic whip. They may print in a line, but it will be a short, MOA sized line. When you see such a line print on the target, adjust seating depth slightly and retest, things will probably get even better.
If you've ever fired a group which printed in a long (2 MOA or better) diagonal, or perhaps a horizontal line, you've seen the effects of a load which is firing slightly inconsistently, and which is also spitting the bullets out in a "straightaway" of the barrel's harmonic whip cycle. Loads which give these results (assuming there aren't other factors causing the pattern) can be corrected by incorporating a more consistently burning amount of powder--usually a greater amount of powder when safe to do so.
Folks often change primers and correct an inconsistent load, but it is my belief that if the proper amount of powder for the recipe at hand is being used, primer swaps will have far less effect on accuracy. And that's where you want to be--a 1/2 MOA load that won't exceed MOA with a hodge-podge mix of primers.
In the example of the 165/H4350 30-06 load mentioned above, all that should be needed to get excellent performance from this recipe in any decent bolt action 30-06 would be seating depth adjustments. By seating the bullet farther into or out of the case, you will be altering the barrel time of the bullet, and hence altering the position in the harmonic whip of the muzzle where the bullet is released.
Thanks for the encouragement, Don. This idea is something that has been noted and pursued by many before me. As Paul Box, senior ballistics tech at Sierra said, Ken Waters has gained some fame and money by publicizing his pet loads for various rifle chamberings. I'm not sure how Ken's load development method compares to mine, and I'm not sure he's even published it.
I hope my explanation as to why I believe various rifles shoot the same recipe well was easy enough to understand.
I've had excellent success at www.snipershide.com with the recommendation of an optimal charge weight .308 win load, the 45.0 grain Varget/175 grain Sierra Matchking/CCI BR primer recipe. About 7 or 8 folks have tested that recipe in their .308's at this time, and all have reported sub MOA performance from it. And that's been in Winchesters, Remingtons, Savages, and some custom rifles, having 1:10 and 1:12.
