Posted: 1/15/2009 2:13:17 PM EDT
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I have seen the couple of examples in other threads (one 5 shot group posted by Mark, and one other), but would like to know from a broader sample–– how is your Stealth upper doing in terms of accuracy? Most useful for the discussion would be someone who has broken in a Stealth, and has personal experience with other custom barrels like Krieger, Shillen, etc. Is the LW barrel in their league? If you have more than one Stealth, is one better than the other?
I shoot 5 shot groups, but understand the value of 10 shot groups. Thanks. |
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.535 edge to edge, minus the two fliers...
Did you measure that group? Hint: Those werent flyers. You might want to take a look at molons thread. Realistically that looks like a .9-1.0 MOA group Quoted:
At the risk of getting it from all directions I'm going to throw in my two cents. Since I don't know anyone here, I don't have any personal bias for or against any of the posters. I'm no expert on AR's, but I am an expert on statistical data analysis and that is at the root of this whole discussion. (Experience = Ph.D. with, depending on how you count it, about 20 years experience.) Whether you are concerned with testing loads, or barrel condition, or sighting, or trigger control or whatever, when you use target analysis you are trying to use a statistical sample (sample population) to make a prediction about overall behavior of future shots (parent population). Assuming the appropriate calculations are done correctly you can then draw some conclusions about the average behavior of future shots within the statistical uncertainties. However, for this to be valid, there are some key points that have to be satisfied. 1) The sample must be representative. In practice this means a couple of things. First you can't arbitrarily throw out shots as "fliers" because they appear way outside the "group";. You can only throw out (and should) shots which you KNOW to be un-representative. For example if someone slaps you on the shoulder just as you pull the trigger. But just because a shot "looks" different does not mean that it can be excluded. Second, the results automatically are representative of all of the statistical variation that goes into the sample. So if, for example, you want compare the performance of two different loads in the same rifle, then you have to get one or more samples (groups or sets of groups) for each of the two loads, with no other differences. In practice can you eliminate every single other variable? No, but you should be able to eliminate the statistically significant ones. Or, at least be aware of and ensure that other variables should contribute equally to the all of the samples for each load. ..snip.. |
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I'm inclined to agree with those who say those weren't fliers.
Vicious, .75-1.25 is a huge spread, in terms of a precision barrel. 1 inch is not "one ragged hole," a phrase used on the website. If you have similar experience with Krieger and Shillen and Lilja, how would you describe their reasonable accuracy expectations? And have you checked the twist rate? thx |
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If you want to compare it to a krieger, and a small lesson in 10-shot groups
Originally Posted By Molon After extensive testing I am of the opinion that 5-shot groups and especially 3-shot groups do far more to bolster our egos than they do to help us evaluate the accuracy of our rifles and ammunition. Below are the two best 3-shot groups I have ever fired from an AR-15 at 100 yards. The groups measure 0.165" and 0.184". So do I have a "less than quarter of minute angle rifle?" Can I shoot groups like this consistently? No way! I had to cull through a whole lot of 3-shot groups to come up with these. 
5-shot groups don't help us that much more either. The groups below measure 0.394" and 0.353". So do I have a "less than half minute of angle rifle?" Not! I would have to discount a whole lot of other 5-shot groups that speak to the contrary to make that claim. 
Now, take a look at the last picture. Every single group in that picture is a 10-shot group fired from 100 yards and every single group in that picture measures less than 1". Can I shoot like that for every single group I fire? No, but with all those groups repeatedly coming in under 1" I am quite confident that the rifle and ammunition used are truly capable of "less than one minute of angle" accuracy. 
Remember Rick Jamison's quotes from the second post in this thread: 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. 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. |
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The group was shot with my hand loads consisting of Hornady 75gr OTM, 24gr of Varget, and the 18". I have found this combination accurate in both 16" and 18" Stealths.
and ammo? That is my base-load also. I chronoed the 24 gr varget with 75 gr hornady Match HPs at 2900 fps out of my 18". They seemed to shoot around 3/4" groups, but I didnt shoot 10 rounds either, generally 5. I don't shoot well enough to do the gun justice, if I shoot 10 rounds Im going to send a couple flyers. |