A standard reloading technique for creating safe ammunition is to start off with a “ladder charge” that starts at the “starting charge weight” and works up to the “max charge weight” in 0.3 or 0.5 grain increments for a given powder and bullet combination. Some data sources only list max charge weight and tell hand loaders to reduce by 10% to calculate the starting charge weight.
Now, in this load workup, a hand loader will normally find two distinct accuracy nodes, one near the starting charge weight, and one near the maximum charge weight. Generally, but not always, these charge weights will be around 8% apart. I don’t know why this happens for sure, but there are a lot of theories about barrel timing and harmonics that make plenty of sense.
So, between those two accuracy nodes, which will be MORE accurate? Here is a rule of thumb that is generally right; the one with the smaller charge weight for “position insensitive” powders such as extruded “stick” powders as it will perform more consistently across a wider temperature range (lower pressure means slightly less effect due to ambient temperature shifts), and conversely for harder to light off ball powders, the heavier charge for more consistent ignition (but you really need to watch the temperature swings for POI shifts). This rule of thumb isn’t hard and fast, but it should serve you well in choosing an accuracy node for your favorite rifle.
Now that I’ve given different advice for two different types of rifle powder, which powder is better? Well generally an extruded powder is easier to get good accuracy from, all else being equal. However all else is almost never equal, and ball powder is MUCH easier to run through a mechanical volumetric powder measure (although even bulky “hard to measure” powders like IMR 4064 have worked out well for me through a Lee Perfect Powder Measure for 308 Win size cases). For something like 223 Rem aka 5.56×45 I actually prefer a ball powder for most of my shooting needs. The charge weights are almost half of a 308 Win charge weight and so the margin of error for a few more or less kernels of powder is magnified in the smaller case. Yes you can get more accurate results hand weighing every single charge, but that takes a dang long time and I’d rather be shooting than reloading most days.
One of the most seductive, and dangerous things, is when the upper accuracy node is just beyond max charge, and you can see groups start to tighten up as you approach max charge. I don’t recommend going beyond max charge in search of accuracy. I know people who do it, but the small advantage they gain from having a bullet go a little bit faster is mostly irrelevant at 600 yards or less.
On the flip side of going over max charge, going under minimum charge is also not recommended unless you are using a powder specifically tested for low density charge weights like H4895, and even then use the load data provided by Hodgdon for those low recoil loads. A light charge with a just slightly too heavy or slightly higher friction coefficient bullet is a bad combination to have some times.
Rarely in my experience, you’ll only get one accuracy node in a load workup, but it has been known to happen. What that means is that there is probably a node under min charge, and another over max charge. If you can fine tune the accuracy at that node, then all is good in your world.
But what do you do if you have a powder and bullet combination that doesn’t seem to have ANY accuracy nodes during your load workup? Change components. The darndest thing happened to Ryan at TLSR with a Savage Hog Hunter, it just wouldn’t shoot 165 and 168gr bullets worth a darn, but would shoot cheap 147-155gr bullets tight. Sometimes all the general wisdom just doesn’t work and you have to try something else. Individual rifles are a just that, individuals, and sometimes you’ll get lucky with a “recipe load” that performs well in a variety of rifles (Dan Newberry’s Optimal Charge Weight load workup method tries to identify those universally good loads). But sometimes you won’t get lucky, and nothing you have on hand will shoot worth a darn, and the only thing left to do is change around components until you find something that works (I recall some famous gun rag writer having to resort to 7mm bullets swaged down to 270 bore for one of his custom 270 Winchester rifles to get it to shoot worth a darn).
Comments are open, what’s the darndest accuracy story you’ve got?