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 the accuracy that I have been able to obtain shooting cast bullets in sporting rifles. For the first two years that I became interested in cast bullet rifle loads, all groups were fired at an outdoor range, while sitting at a wooden bench, my elbows resting on the bench, roughly equivalent to a field sitting position (as my local range does not permit actual field shooting). Sighting equipment was either irons, or low power hunting telescopes.
Average group size from 2014 through 2016 was calculated. This is the good, the bad, and the ugly, all lumped together, representing 2,500 shots. Average accuracy for seven rifles was 5.0 MOA, with a standard deviation of 2.0 MOA. Ouch!
At this point, I fired a 100 shot comparison data base with my Anschutz 1710 .22lr, shooting in the same manner, although aided by a target telescope. 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 fired 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.
I consoled myself with the thought that if my cast bullet loads could hold a consistent 4 MOA in this "field style" of shooting, that I should be satisfied with them, as they would be grouping within a MOA of what the highly developed .22 long rifle cartridge can do in my hands. It seemed unlikely that I could sit in my garage and concoct anything to significantly better 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. While I didn't expect that level of accuracy, I thought that a 5 MOA average should allow further refinement. 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! Recalling that warning, published in the 1979 NRA book "Cast Bullets", I loaded the lead pot with linotype. This was key to improving my results, as the good advice immediately bore fruit.
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 (three 50 yard ten shot groups).
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. The simplest way to do this is by dropping bullets from the mold directly into a bucket of water, but unless your casting rhythm and mold release is absolutely consistent, substantial variations in hardness may result. For precise control, a toaster oven can be employed.
Air cooled bullets cast from scrounged alloy measured BHN 11. Baking for 30 minutes at 440 F, followed by a cold water quench, produced substantial hardening.
They weighed 298 grains, so I cut the powder charge by half a grain, and loaded them up. Five days later (to allow them time to fully harden) I shot this group:
With 10 shots into 2.75 MOA, it lay well within the grouping provided by linotype. Changing to adequate alloy - linotype or via heat treating - made a real difference. I became interested in what a rifle firing cast bullet ammunition could do, independent of my own skill (or lack thereof).
In late 2018, I mounted a Weaver 20X scope on my little Sauer 101 "Scandic" .243 Winchester carbine, and fired it over sandbags fore and aft. This pretty much took me out of the picture, to focus on rifle and ammunition performance alone.
A load for the .243 Winchester.
Sauer 101 Scandic (19 1/2" barrel, 1 in 10" twist) - with 20X Weaver scope.
Bullet: SAECO 243, cast of linotype, and sized to 0.244".
Weight 80.5 grains, with GC and lube.
Primer: S&B Large Rifle Magnum
Powder: Alliant #2400, 12.3 grains (thrown from a Little Dandy #15 rotor).
Light taper crimp. Cartridge OAL 2.650"
1656 fps. Average 1.34 MOA, standard deviation of 0.44 MOA, over a 70 shot database (fourteen 100 yard five shot groups).
This is a typical 100 yard benchrest group.
Not "sub MOA", but respectable. At 100 yards, the smallest of 35 five shot groups was 0.75", the largest 2.25". As the preacher says, "Let's strap on the truth, and tell it like it is."
Removing the T20, I substituted a 3X Leupold, and then fired 25 rounds with the rifle cradled in my hands,
These five 5 shot 100 yard groups averaged 2.04 MOA with a SD of 0.64, very close to what the Anschutz and .22lr ammunition delivered. Cast bullets reward those who are interested in them for what they are, and who are willing to spend the necessary time to hone their casting and loading skills.