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 comparison 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 in field shooting, 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 (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. 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".
Lt. Col. Jeff Cooper once commented:
"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."
This is a concise explaination of why I prefer to shoot field style, as the combination of shooter/rifle/ammunition determines if you can hit anything. Howevcer, it also makes the case for a full "bench rest" technique, when developing loads.
In late 2018, I mounted a Weaver 20X scope on a little Sauer 101 "Scandic" .243 Winchester carbine, and fired it over sandbags fore and aft. This pretty much took me out of the equation, for pure rifle/ammunition testing. 511 shots later, I came up with this:
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.
At 100 yards, the smallest of thirty five shot groups fired with three different loads was 0.75", the largest 2.25". It is nice to know that the little carbine will hold 2 1/4 MOA with a 95% confidence level.
What can I expect when shooting in the field? The range that I have access to insists that we shoot from a bench, but I believe that firing with my elbows rested on the bench, with the rifle cradled in my hands, and pulled against my shouler, is roughly analogous to a field "sitting" position. I removed the T20, and substituted a 3X Leupold. I then fired 25 rounds "field style".
Here is a 2.25" 100 yard "field" group. The 25 shots averaged 2.04 MOA with a SD of 0.64, for a 95% confidence level of 3.3 MOA. This is just over 1 MOA larger than the benchrest grouping.
Field accuracy of 3.5 MOA is not to be scorned. Recall George Farr, at the 1921 National Matches.
Cast bullet loads which provide sufficent accuracy for meaningful practice have the substantial benefit of negligible barrel wear and tear, which is particulary important with a barrel burner like the .243 Winchester. It is one of the primary reasons that cast bullet rifle loads interest me.
Anyone seeking to improve their ability to create accurate cast bullet ammunition MUST obtain a copy of "Cast Bullets", first published by the NRA in 1979, Library of Congress Catalog Card Number 79-89301. This contains the extensive work and invaluable observations of Col. Harrison.