Originally Posted by FiveInADime
This is good stuff. You're messing with us, right? 3-shot groups can mean just as much as 10 shot groups if you shoot enough of them. If you shoot 20 3-shot groups and the bullets all land in the same place relative to POA, then it's the same as shooting 6 10-shot groups with all the bullets landing in the same place relative to POA. Now, what rifle, heavy barrel or not can shoot 10-consecutive shots in a minute without the barrel heating to branding iron levels?
If you shoot 3 Sub-MOA 5-shot groups in a row, that's the same as shooting a 15-shot Sub-MOA group. Happens more often than some people in this thread think even with sporter rifles. I see guys at the range shooting heavy bolt-action rifles into 3/4"-1" 5-shot groups at 200 yards with regularity. I have a .243 that I can easily count on 1.5" groups at 200 yards. That's slow-fired 5-shot groups. Nothing special other than some painstaking work at the reloading bench.
Shoot your five three shot groups all at the same target, then measure.
Shooting ten shots in a row won't hurt anything. Even at a fairly rapid pace. People will use the heat as an excuse for why their ten shot group is 1.5-2 MOA instead of whatever their slow fired 3 shot group was. Truth is their 'MOA' rifle is really not.
There are stories of a single bullet that for no explained reason flies out of what might have been a tight cluster. This often occurs with a three-shot string and many times with a five-shot string. If you're lucky enough to fire a group without a flier, you can end up with a very tight group. However, usually what happens if another five or seven shots are fired to complete a 10-shot string, other bullets fill in the space between the main group and the flier to make a reasonably rounded group. Ten shots are a more reliable indicator when it comes to predicting what a load is likely to do in the future.
The problem with 10-shot groups is that when you report them, everyone thinks you aren't shooting very well or that the ammunition is not good because the group sizes are so much larger than three- or five-shot groups. Also, when we're firing three- or five-shot groups with a flier, it is only natural to assume that it was caused by a flinch or "pulling" the shot. Therefore, since the flier was our own fault, the tendency is to eliminate it from any reporting of group size.
This is one of the advantages of using a machine rest... The machine rest reduces the human element.
After using this machine rest for several years, I have determined that a 1.5-inch 10-shot group at 100 yards... is a good one.
- Rick Jamison, the author of the Precision Reloading column in Shooting Times magazine
I'm betting Rick Jamison has done more rifle testing than most of us. Seeing as how he gets paid and financed to do it.