Just for the sake of closure to my point, I was talking about precision and not barrel life. In Molon's tests the 16" 1:9 Colt HBAR and 14.5" 1:7 SOCOM averaged sub-moa groups but I guess that's kind of irrelevant now.
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Just for the sake of closure to my point, I was talking about precision and not barrel life. In Molon's tests the 16" 1:9 Colt HBAR and 14.5" 1:7 SOCOM averaged sub-moa groups but I guess that's kind of irrelevant now.
ES actually doesn't even do that consistently. With some groups you can draw the circle (which intersects tangentially the 2 rounds which have the ES), and have some rounds outside of that circle.
Here is a poor quality diagram I drew around one of my groups.
radius2.JPG
I miss molon. Need to re-read some of his threads. Also need to build up my Colt SOCOM upper.
Last edited by JoshNC; 02-07-17 at 02:10.
SLG Defense 07/02 FFL/SOT
With the exception of quality stainless barrels it is my opinion to always get chrome lined barrels on AR-15's. They don't have to be hammer forged necessarily, but should always be chrome lined if not stainless.
"Give me Liberty, or give me Death!" - Patrick Henry
Actually, Mist Wolf is correct.
The Extreme Spread (ES) is the diameter of the smallest circle that can be placed on a group that encloses all the shots. No hole will be outside the ES, by definition.
You are referring to extreme horizontal or extreme vertical spread (EHS or EVS).
Your ES is this:
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Last edited by lysander; 02-07-17 at 16:44.
I'm not following.
Extreme spread is defined as the maximum distance between the center of any two shots within the group. It is actually not a circle, it is a line. It is the dotted yellow line in my graph. It is what you see people online measuring with their calipers laying over their magnificent 3 shot group.
The blue circle in the graph would be the CCR, or covering circle radius. Sometimes the diameter of the CCR is equal to the ES. Sometimes it is not. That was the point I was trying to make when Mistwolf said that ES gives the diameter of the circle which will cover the grouping.
Last edited by P2000; 02-07-17 at 20:50. Reason: added quote
If money is tight, then keep saving your money. This is a buyer's market and there is absolutely no reason not to get a solid AR.
Don't waste money on the Expanse or the OEM. Get a completed carbine. If you are counting pennies to get that, then you might as well look at something else since you are still going to need magazines and ammo.
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You measured the wrong shots. Your group shown is smaller than what it should be. ES is measured from the center of holes like lysander showed (his looks a little big, but I think he was making a point).
It's the distance between the farthest 2 shots, not any 2, or it wouldn't be "extreme" spread.
And then there's this. Save up for a few extra months. Cut costs elsewhere in life to get something good.
Last edited by MegademiC; 02-08-17 at 06:00.
Unfortunately (as far as AR's go)I'm in Canada so selection is limited. There are a lot of high quality rifles available but for my budget I'm looking at the Expanse OEM-1, S&W 15, Norinco, Anderson and possibly a couple of others and for a couple of hundred more a Sig M400. As I mentioned since I would change the furniture anyway to suit my taste I was looking at the 6920 over the Expanse. TC
Negative. Hold a ruler up to your screen. Eyes can play tricks on us, overestimating height, and underestimating width. The 2 shots separated by the yellow dotted line are the 2 shots in the group with the maximum distance between them, the extreme spread. OnTarget software puts a faint black line between the 2 shots, also indicating they are the ES.
"the maximum distance between the center of any two shots within the group"
Here is a drawing of a group, illustrating the same concept. It is easier to see in this drawing. ES of this group would be the distance between shot A and B. If the line AB is turned into the diameter of a circle, the circle is not large enough to cover the whole group. Even if you shift the circle, it cannot cover the whole group.
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