January 04, 2011
A competition shooter's lessons on building top hunting ammo
In the very beginning of his load development, the author doesn't even hang a target. He just tests muzzle velocities and judges chamber pressures.
Whether it's for competition use or hunting, we all want the best possible performance from our ammunition. While normally this column concentrates on competition shooting, the approach to handloading I'm about to describe is geared toward hunters.
When choosing and then tuning a handload for a hunt, there are several factors to consider. First, and always, is accuracy, but bullet performance on impact is critical in hunting. Still, shot-group consistency is key. The only reason I mention this is that it's not unreasonable to test a hunting rifle with "match" ammo to help determine a yardstick--how well your rifle can actually shoot. You can then gauge group sizes of hunting ammo relative to that standard.
Hunting ammunition should also hit hard. With the quality and selection of propellants we have, though, there's never a reason to sacrifice velocity for accuracy. Velocity consistency is a key factor in impact consistency, especially at extended ranges.
It's important to have a "cold" zero on a hunting rifle. The goal on any big game hunt is to end it with one shot. Many hunting rifles, especially those with lighter-weight barrels, exhibit a tendency to shift impacts as the steel temperature changes.
Typically, the first round from a cold barrel will be a little outside the shot group location you'll get from the next few rounds, and then there may be another change as more shots are fired. If the barrel is clean to start with, then the first few rounds were necessary to foul the barrel and settle it in. If that's not a factor, then what is happening is that the barrel is "looking" in a different direction as it heats up.
Note any such tendencies in testing. It goes without saying that the wise hunter will adjust his rifle's zero accordingly. This also factors into accurately evaluating group size. Ideally, if we want to use a 10-shot group as a standard, then that group would be acquired via 10 shots through a cold barrel.
Barrel choice can be a big factor in this aspect of performance. Generally, the higher quality the barrel (not necessarily the heavier its contour) the more consistently it will perform, starting with the first shot. A properly stress-relieved barrel, even at a very light weight, shouldn't show much if any difference in impact as its temperature increases.
If I am trying a new cartridge, I throw some different charges into a case to get some idea of what the volume will be. I do this just to get an idea of where to start: How much of which propellants will fill the case.
One thing I pay attention to is propellant consistency, how consistent velocities will be at different temperatures. Some propellants are decidedly less sensitive to ambient temperatures than others. This can be a huge factor for the hunter traveling to the hot Southwest when he's from, say, the upper Midwest. It's a lesson I learned from competition shooting: I have lost, and also perhaps won, tournaments because of propellant behavior in hotter and colder weather.
To keep this as simple as possible, let's assume I have settled on the best powder. I chronograph published starting loads, working up to the muzzle velocity I want (and I don't try to push cartridges as fast as they will go). At this point, I'm not even using a target.
I use new brass for load development. New brass will not show the pressure once-fired brass does. I'll have five new cases to start with, and I will use those same five cases as things progress.
When I seat the primers after that first firing, I can easily tell the kind of pressure I have. Many people measure case head expansion and look at fired primer condition (how flattened it is), but this is my test because how a new primer fits the pocket of a fired case directly reflects on case head expansion.
This is why I use these same cases over and over. Doing so lets me duplicate the fatigue I can expect in subsequent loadings. Even though for a hunting trip we may be using new or once-fired brass, this is valuable information.
After I've fired these five on the new brass, I go up a grain or half grain, load them again, shoot them again, then feel the primers seat again. I also now have a velocity readout. Five shots won't give me a standard deviation worth looking at, but I can see if it's a big spread.
After I have found a load that is producing within the area I expect--velocity-wise and also within my standards for pressure--I will load up 15 of that one and then will go up a half grain and load 15 like that, and then will go down a half grain and load up 15 more. I label them A, B and C, with A the mildest. Then I clean the barrel and go to the range to hang a target.
The distance at which I will test this ammunition depends, of course, on how far I anticipate shooting on a hunt. I usually test at 300 yards. I begin with the mildest load I brought and chronograph two to three rounds of it to get a zero. I'll then fire 10 rounds for a group, all done over a chronograph.
The reason I have loaded 15 of each test is that I shoot two to three for zero, 10 for the test--leaving me a couple rounds each. I can then measure the overall length, pull the bullet, reweigh the charge, and that way I have double-checked myself. At the range I mark the cartridge box and line up the rounds and fired cases so I know the loading order and can review the test progression. I mark the case heads so I can't mix them.
If I test three loads at a time, that's about 40 shots, and that's a good test. I don't want to shoot more than 50 rounds of full-power ammo without cleaning the barrel. Obviously, if the cartridge is something over-bore, the barrel must be cleaned more frequently for a fair evaluation.
Let's say loads B and C shot better and closer to the same points of impact than A. I'll then come back with the B and the C load again and will have made a change, like a different primer in the B load. That has become load B1. If the C load (the hottest) showed no pressure concerns, I might bump that one up half a grain (staying within published maximums, of course) to create a D load.
I may or may not do any experimentation with bullet seating depths. Magazine-length restrictions and other factors may not allow it. I do not recommend seating bullets into the lands for a hunting rifle.
Let's say I went out again
and the B and C load gave me good standard deviations, and the B1 load (the primer change) gave me a poorer SD. Let's say I didn't like the D load because when I seated the primers again in those cases, they felt a little looser, and that was the third load on them. The extra half grain was too much.
That makes me want to lean toward the B load, which was a half grain less than the C load. From this point it's more group confirmation and confirming zero, and then packing up to go hunting.