spandit Posted May 3, 2015 Author Report Share Posted May 3, 2015 Thanks! Was initially worried about the difference but if you look again, the extreme spread on that target (the Hormady one) is 1.38" (or 1.385") so spot on. The difficulty arises that if, for example, I'd shot 9 through the same hole with one flyer, it would give an awful group when actually the shooter/rifle is pretty accurate. I do show both group sizes but the graphic only illustrates one. I can write options to change that The group size I calculated uses mean radius. This means it works out how far from the average of the group each shot is & then averages those. It's not something I made up - got it from Ballistipedia! Quote Link to comment Share on other sites More sharing options...
1066 Posted May 3, 2015 Report Share Posted May 3, 2015 I know the theory but a group size should be something you can compare, apples to apples, not apples to oranges. To my mind, a group is 5 shots at 100yds, warts and all. Measure the outside edge of the two furthest apart holes then subtract the calibre. This can then be compared with any other group size. http://ukvarminting.com/forums/topic/28856-ukbra-100-yard-benchrest-saturday-4th-april-2015/?hl=results http://www.freewebs.com/ukbra/currentrecords.htm I know it's not always possible to shoot at 100yds - so a calculated pro-rata MOA is reasonably comparable, but a .5 moa at 50 yards will not necessarily give you a 3.25" group at 300 yards. Good to see five shot groups, three shot groups are significantly easier, but the flyers shouldn't be discounted, they can give you valuable information - is the bullet borderline stable, is there a significant velocity spread, excessive bullet runout, you the shooter, bedding etc. Remember "internet" groups are always sub .5moa, real world five shot groups seldom are, especially if there are more than two groups on the same sheet of paper. Of course you can often claim really tight groups if you shoot three shots and discount the flyer and the one you pulled off. Quote Link to comment Share on other sites More sharing options...
spandit Posted May 3, 2015 Author Report Share Posted May 3, 2015 It's not discounting the flyers, it just doesn't ruin the rest of the good shooting. These would all have hit a fox in the right place (although not sure why it's shooting so low - it was zeroed at 100yds so should only be .2" low at 50...) A good read of this might clarify (or confuse) - it's where I got most of my calculations from http://ballistipedia.com/index.php?title=Describing_Precision Quote Link to comment Share on other sites More sharing options...
1066 Posted May 4, 2015 Report Share Posted May 4, 2015 (edited) It's not discounting the flyers, it just doesn't ruin the rest of the good shooting. These would all have hit a fox in the right place (although not sure why it's shooting so low - it was zeroed at 100yds so should only be .2" low at 50...) A good read of this might clarify (or confuse) - it's where I got most of my calculations from That's an interesting read - especially the analysis concerning 3 shot groups, should be required reading. .http://www.ar15.com/mobile/topic.html?b=3&f=118&t=279218 The flyers tell you more about the load/shooter/rifle than the rest of the group. If you look at your Hornday group, not too bad except the flyer, but look at the hole the flyer has made, not quite the same as the other holes. It looks like there is a certain amount of yaw, this may be due to a marginally stabilised bullet, excessive bullet run-out, loading a case with a split neck, low powder charge etc. If your aim is to find a satisfactory round that will be easy to load and fairly consistent I would suggest you ditch all your odd cases and stick to one batch, all the same, not just the same make but from the same batch (buy a hundred Lapua cases and be done with it) Find a good mid range bullet suitable for the twist rate of your barrel, not on the ragged edge of what might stabilise on a good day. Practice using the measure so you get consistent drops within .2 grain (You would be better to weigh each one until you have your load/rifle shooting good consistent groups) The Lee measure works as well as any other measure and better than many. Shoot from a consistent stable platform. Your groups show an element of vertical stringing, this is often due to using a bipod or resting the rifle on a hard surface rather than a sandbag. Also try and shoot at a greater distance, scopes often have parallax problems at shorter ranges Discount any load that throws unexplained flyers, and yes, the flyers all count in the group size. Edited May 4, 2015 by 1066 Quote Link to comment Share on other sites More sharing options...
spandit Posted May 4, 2015 Author Report Share Posted May 4, 2015 Interesting about the hole, although I was only using A4 copy paper and it was fluttering about a bit in the wind so might not have been laid flat when the bullet went through it. Busy updating the software to show the correct extreme spread (which I don't think is showing correctly at the moment) as well as some other parameters... I'll look into a sandbag, I was shooting from my rifle cradle which is fairly rigid Quote Link to comment Share on other sites More sharing options...
spandit Posted May 4, 2015 Author Report Share Posted May 4, 2015 Grrrr... different PHP versions on the remote and local servers so had to rewrite a few functions. Up to 607 lines now but should work: www.creffield.com/ballistics/target.php Quote Link to comment Share on other sites More sharing options...
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