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#11 | ||
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Junior Member
Join Date: Nov 2014
Posts: 6
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In my experience, a high SD load is less likely to be accurate. But there are no hard and fast rules -- a low SD load can be inaccurate, and a high SD load can be really accurate.
It's fun to measure the SD and interesting to see how it changes as you get towards the hotter end (usually) but ultimately once a load is "fast enough" I go by the target not the SD. |
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#12 | ||
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Member
Join Date: Dec 2015
Posts: 596
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General rule of thumb is you want a SD of 15 for 600 yards, and 10 for 1000, over 22 shots.
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#13 | |||
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Senior Member
Join Date: Feb 2013
Location: Not Far Enough from the City
Posts: 6,202
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Here's an interesting article about the effects of differing standard deviations at extended range. Good vs. better vs. great, if you will.
While SD matters, the data suggests a point of diminishing return. https://precisionrifleblog.com/2015/...oes-sd-matter/ |
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#14 | ||
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Senior Member
Join Date: Feb 2013
Posts: 19,255
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Quote:
But if the load is not showing a 3/4" vertical spread, then who cares? Case the numbers if you want, but it the load shoots a small group, it is accurate. |
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#15 | ||
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Senior Member
Join Date: Feb 2013
Posts: 19,255
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Quote:
For long range match or similar, I would set POA and POI for when the {POI settles down. But document the POA to POI difference for the first couple shots to compensate. Hunting, I want the least things to think about for the first shot. So sight in for maximum point blank zero, POA = POI for first shot. At the range, I use 100 yard zero, distance charts, and can dial or hold off for first cold bore shot. |
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#16 | |||
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Old Timer
Join Date: Oct 2011
Location: Millersville
Posts: 313
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Neck tension was the biggest problem for me and getting numbers and groups to line up. Retired my old brass and began anew. The bullet seating effort was very noticeable between cases. Annealing helped but wasn't a cure.
__________________
A free man needs no permits or papers |
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#17 | ||
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Senior Member
Join Date: May 2012
Location: Eldersburg
Posts: 6,774
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Quote:
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#18 | ||
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Senior Member
Join Date: Feb 2013
Posts: 19,255
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Quote:
A 1/2 MOA rifle will be shooting a 1.75 inch group. You have to be a pretty bad shooter to make that a miss. ![]() |
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#19 | ||
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Senior Member
Join Date: Aug 2011
Location: MD
Posts: 5,535
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Quote:
So shooting buddy was getting a sticky bolt, dropped powder charge by .7gr to get rid of that. Still grouped well. He is loading using k&m press with force pack (measures force to seat a bullet). First 20 pounds were 28-36lbs, the rest were double that pressure. One would assume varying neck tension would drive the seating force, yes? His vertical at 600 was the x ring....how does that happen? Doesnt make sense in my brain. Dropped a 599-41x! For those that dont know fclass, x ring is 3 inches. |
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#20 | ||
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Senior Member
Join Date: May 2012
Location: Eldersburg
Posts: 6,774
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I didn't take the time to run the numbers but, take that 1/2 MOA rifle shooting a 1.75" group and add the .7" difference in drop and you already have 2.45". Now, factor in a really good shooter with about a 1 MOA hold and you have 4.2". Pretty easy to miss a groundhog when optimal conditions give you only a 4.2" group, and that is without factoring in outside conditions like wind.
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