It is well known that the more shots you fire, the bigger your group will be. Rifles print their shots in a roughly Gaussian distribution. To get a realistic assessment of the accuracy of any rifle/load/shooter combination, at least 10 shots are needed. Two groups will give you a better idea than one. Averaging many such groups and determining their standard deviation is even better. McMillan has pointed out that firing only a small number of shots, coupled with "the human tendency" to report "the best results I've ever gotten" as "typical results" obscures the truth.
Here I will present an unflinching view of what sort of "field" accuracy I have been able to obtain shooting cast bullets in sporting rifles. These groups were fired at an outdoor range, while sitting at a wooden bench, my elbows resting on the bench.
Average group size during rifle load development from 1/4/14 to 9/28/16 was calculated. This is the good, the bad, and the ugly, all lumped together. The data represents 2,532 shots. The average accuracy for seven rifles was around 5.0 MOA, with a standard deviation of 2.0 MOA. Individual rifles ranged from 8.6 MOA, SD 3.1, to 4.0 MOA, SD 1.7.
I then fired a 100 shot data base with my Anschutz 1710 .22lr, shooting in the same "field" style. My smallest 10 shot, 100 yard group was 1.375", and the largest 2.5". The average for all was 2.0 MOA, with a standard deviation of 0.54. The normal distribution tells us there is a 97.5% probability that any subsequent shots will fall within a "cone of fire" two standard deviations larger than the average, or just over 3 MOA.
Now, you don't have to be a math freak to make these calculations. I have trouble with simple arithmetic, so I just Google "online standard deviation calculator", enter my extreme spreads, and then hit the "calculate" button. There may be better ways to assess your rifle's accuracy, but none are simpler.
So: if my cast bullet loads can hold a consistent 4 MOA, I should be satisfied with them, as they will be grouping within a MOA of what the highly developed .22 long rifle cartridge can do in my hands. It is unlikely that I can sit in my garage and concoct anything that significantly betters RWS and Federal.
This is contrary to the perception that one might get from browsing the internet, where "sub MOA" groups are spoken of as routine, if not expected. Should your own results fall closer to mine than that of the "sub MOA" crowd, please do not despair. Firing cast bullets from rifles has a learning curve which requires persistence to master, along with a tolerance for frustration.
I am assuming that you fully understand the major aspects of casting lead bullets, handloading ammunition, and handling firearms. If you are a novice in any of these areas, please do not proceed until you have developed a realistic appreciation of their dangers. You should also know of the controversies which swirl about the creation of reduced loads. If after appropriate study and due reflection you have decided that the inherent risk is acceptable to you (and to those around you), read on.
Decades ago, Col. E.H. Harrison, USA (ret.), who conducted extensive and elegant research into the use of cast bullets in rifles, stated "cast bullet loads require the strongest lead alloys practicable. Disregarding this causes failure. Tradition, regrettably kept alive in published information, has been a heavy handicap." My initial results, generally employing scrap alloy, certainly support his contention! Remembering that warning, first published in the 1979 NRA book "Cast Bullets", I loaded up the lead pot with linotype. This was key to my first success:
A load for the .358 Winchester.
Ruger 77 Mk II Frontier (16 1/2" barrel, 1 in 12" twist) - with forward mounted 4X Weaver scope.
Bullet: Accurate Molds 36-302DG gas checked, cast of linotype, and sized to 0.360"
Weight 278.5 grains, with GC and lube.
Primer: S&B Large Rifle Magnum
Powder: Accurate Arms 4064, 38.5 grains
Light roll crimp. Cartridge OAL 2.755"
1735 fps - average 3.1 MOA, standard deviation 0.16 MOA over a 30 shot database.
Here's ten shots on a standard NRA 50 yard smallbore rifle target. Groups are still good with 39.0 grains of powder, but open sharply at 40.0.
Nothing fills out a mold like linotype, and the results speak for themselves, but the stuff is expensive. Dennis Marshall and others have told us for years that heat treating will allow the use of softer, less expensive alloys. This is worth considering, as it allows you to use that scrap which you have collected in full throttle loads. A batch of these bullets cast from scrounged alloy measured BHN 11. Baking for 30 minutes in a toaster oven set to 440 F, followed by a cold water quench, produced substantial hardening.
They weighed 298 grains, so I cut the powder charge half a grain, and loaded them up. Five days later (to allow them to get roughly as hard as linotype) I shot this group:
With 10 shots into 2.75 MOA, it lies well within the expected grouping for linotype. While I am pleased, note that a true "sub MOA" rifle/load would print within the quarter at twice the range. As the preacher says, let's "strap on the truth, and tell it like it is".
It's easy to become obsessed with tight groups while developing loads, so let's recall the comments of Lt. Col. Jeff Cooper:
"While accuracy is the great god of the rifleman, its single-minded pursuit may obscure some facts of life. A one minute weapon will strike within 1 inch its point of aim at 200 yards, while a two minute piece will strike within 2. You can't see that increment with anything but a high-power telescope, and you couldn't hold that close from any field position."
Back in 1921, 62 year old George Farr ambled up to the firing line at the National Matches around 4:30 pm, assumed the prone position with a 1903 Springfield, and over the next hour and 40 minutes, punched 70 consecutive bulls at 1,000 yards. The black was a 36" circle in those days. We're still talking about that performance! If you can hold an honest 3.5 MOA, in fading light and under the pressure of competition, I'll shake your hand, and call you a rifleman.