joeb33050
posted this
21 August 2018
I do all of my test shooting firing ten-shot groups, both rifle and pistol. My feeling is that there is no such thing as a "lucky" ten-shot group, so while I might also shoot those rounds over the chronograph so that I know if the ballistic uniformity is good, more than anything else I want to see if the group is round, with a dense center and that the distribution of the shots is circular-normal.
7.15.2 WHAT DOES "IN CONTROL" MEAN?
In order for accuracy testing to yield true results, the load must be "in control". (For the purposes of this discussion, “load” includes the gun, sights, rest and all components such as powder, primer, bullet, etc.)
The term "in control" means that the test results come from one distribution and not two or more distributions. If we test with two different bullets or lubes or powders or scopes at one time, then we are testing two loads, and will see what appear to be big groups. Maybe we're shooting small groups with each load, superimposed on each other making a big group.
For example, groups with three holes in one place and two holes in another place or groups that are taller than they are wide are symptoms of the load not being "in control".
Groups shot with loads that are "in control" are round, on average, in the long run.
It is difficult to impossible to determine if one or two groups are round by just looking at them. Size doesn't come into it; big groups may be "in control" and small groups may not.
One way to find out if your loads are "in control" and if your test results are true is to shoot a lot of shots into one target The group of a lot of shots will be pretty round if the load is "in control".
Another way is to shoot a number of groups using a backer. Put a piece of paper or a target on the target frame, put a target on top, and shoot. Then remove the record target, align another record target on the backer and shoot that record target. Keep this up, noting pulled shots on the record targets. When done you'll have the set of record targets and the backer with all shots fired at the record targets. Note the pulled shots on the backer. The holes in the backer, less the pulled shots, should form a roughly round group.
Groups that appear to be not in control are a sign that something is amiss with the load. Let the search for the culprit begin.
I don't do ladder testing, but shoot ten-shot groups on paper over a range of charge weights, starting on the low end and in a case the size of the .3-'06 increase in full grain increments, one ten-shot group at a time. An iron-sighted '03 Springfield, Winchester 54 or Model 70 should shoot 2-inch or smaller 10-shot groups off sandbags at 100 yards if the load is working. If the group is round, but loose, over 2-1/2" I look at bore condition for leading and check bullet fit. Next step is to adjust bullet diameter and hardness, usually a bit fatter, softer and slower. I then try again. If a load shows promise under 2" I'll try again also bracketing the charge +/- 1/2 grain either way. If the bullet holes are not round I will increase the charge a bit and try again. #311299 is stable at subsonic velocity in a ten-inch twist.
I'm not a big fan out of frequent cleaning if a load is working well. If trying a new load, lube, bullet, alloy or powder I'll run a dry patch through the bore after 20 shots, feel how it goes, examine the patch.
K.I.S.S. principle.
