Re: Some pics of groups, and some questions...results from this mornin
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I will check the bedding again. recoil lug does have room in front and on the sides.
I think I will start shooting 4 shot groups, and that may help a little more.
How often do you guys clean your big guns while shooting? is there a certain # of shots before you clean? kind of a benchmark people go by?
[/ QUOTE ]Good comments, questions...here's answers, comments.
Bedding; the bottom of the recoil lug must not bottom out. When it does, the bottom, front part of the receiver won't be held down solid and perfect in its part of the epoxy. Always have 1/32nd inch of tape on the lug's bottom before putting the metal in the gooey epoxy. The front and sides should have full contact; that helps prevents receiver twisting (especially on round ones like Remington and Savage) and front-back movement.
Number of shots in a group; the more the merrier....er..I mean meaningful. Statistically speaking, one needs at least 15 shots in a single group if one expects it to be at least 80% reliable; that is at least 80% of the groups will be smaller than a 15-shot one is. And if one shoots enough shots in a single group, it will be a one-hole group...even if it's at 200 yards and 4 inches in outside diameter. I talked with one of the ballistic engineers at Lake City Arsenal years ago about testing ammo for accuracy. We talked about what's called the 10 - 20 - 30 - 40 percent rule; 40% of all the shots will go inside the middle 40% diameter of the whole group, 30% inside that and the next 30% which means 70% of all shots will go inside the 70% diameter of the whole group. Adding the next 20% means 90% of all shots will go inside 90% of the whole group's diameter. And of course 10% of the shots will go outside the 90% circle but inside the group's diameter. This is very obvious if you shoot 200 to 300 shots per test group, determine group center, then calculate the mean radius each shot is from the actual group center. Speaking of group centers, did anyone ever shoot four 5-shot groups, each on a different target atop one target to record all 20 shots, but using the same aiming point, then compare the 20-shot composite group to each one of the 5-shot groups? Like the man says, "Like one-hole groups? Shoot only 1-shot or 300-shot groups. Like high levels of confidence? Shoot many-shot groups." The more shots per group there are the higher level of confidence one represents what accuracy is. Any single group of less than 10 to 15 shots is not above 50% confidence; half the groups fired will be bigger and half smaller. A single 3-shot group has a very low confidence level and for ammo/rifle evaluation purposes is only an indicator that great accuracy may exist - but note that a 50-shot 2-MOA group will have several 3-shot clusters of about 1/3rd MOA each. I know, we usually don't have the resources to shoot a few hundred shots into one group to test for accuracy; that's why I use 15 shots as a compromise.
How often to clean....depends on when the ammo fouls the bore enough that you notice accuracy falling off. Some powders really cause problems in about 30 shots (IMR3031 and some AA ball powders); others will go 1000 rounds or more (IMR's 4895. 4064, 4320, 4350 and some WW ball powders {so I've been told}). I'm not aware of any powder that won't go at least 20 shots with good accuracy. Jacket (copper) fouling usually doesn't cause accuracy problems; it prevents them - especially with a rough bore that needs to have its micro pits filled in with jacket material so no more bullets will have copper scraped off them and they'll be well balanced.
