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Joined: Mar 2006
Posts: 14,550 Likes: 7
Campfire Outfitter
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Campfire Outfitter
Joined: Mar 2006
Posts: 14,550 Likes: 7 |
My scopes aren't adjustable for parallax, and the Leupold ones are nominally set to be parallax free at 150 yds. Is there a theoretical or practical maximum parallax error at 100 & 200 yds.? Yes. the maximum parallax error E at a given target distance t for a scope which is parallax-free at distance p and has an objective lens diameter D is given by the equation E = 0.5 D (abs(t-p))/p So, for example, if you have a scope with a 40 mm objective lens, parallax free at 150 yards, maximum parallax error at 200 is E= 0.5x40 (abs(200-150))/150 =6 2/3 mm Similarly, for a target at 100 E= 0.5x40 (abs(100-150))/150 =6 2/3 mm That is to say, if your eye position is at the edge of the exit pupil, you could be as much as 6 2/3 mm off at these distances, in these particular examples. Thanks. So it sounds like the maximum in this example that parallax alone could add to a group at 100 or 200 yds. is about 1/2". Plus or minis 1/2”, so maximum possible error between multiple shots in a group would be 1”. And that depends on the true parallax-free distance (which may not be as advertised), and the size of objective lens.
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Joined: Jan 2001
Posts: 4,313
Campfire Tracker
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Campfire Tracker
Joined: Jan 2001
Posts: 4,313 |
(6-2/3 mm x 2)/25.4 = 0.525"
What am I missing that would double the size again?
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Joined: Mar 2006
Posts: 14,550 Likes: 7
Campfire Outfitter
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Campfire Outfitter
Joined: Mar 2006
Posts: 14,550 Likes: 7 |
(6-2/3 mm x 2)/25.4 = 0.525"
What am I missing that would double the size again? Nothing. You’re right. For some reason I equated ~6.5mm to 1/2” in my head...
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Joined: Oct 2016
Posts: 428
Campfire Member
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Campfire Member
Joined: Oct 2016
Posts: 428 |
Me thinks country boy is a pretty sharp Dude and maybe sharper than you think ! My 243 Hawkeye does it too and I believe after reading this thread it could be 69 years and NOT holding !Shoot quick and killum dead Country Boy
“To account nothing of one's self, and to think always kindly and highly of others, this is great and perfect wisdom.”
― Thomas à Kempis, The Imitation of Christ
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Joined: Feb 2008
Posts: 1,168
Campfire Regular
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OP
Campfire Regular
Joined: Feb 2008
Posts: 1,168 |
Update:
Between the crappy weather and work and family obligations, I haven't been able to shoot in over 3 weeks, but I finally caught a break this morning and made a run to the farm.
Since my last range session, I've cleaned the barrel, checked the action screws, checked the scope mounts and carefully loaded some more ammo. When I set up to shoot today, I paid close attention to the wind and changed how I placed the rifle on my sand bags. I'm not sure which of these thing(s) was the problem, but apparently I fixed something!!!!!
The first 3-shot group at 200 yd was just over 1.25" with a 140 accubond handload. I followed that up with a 2" group with a different handload (150 ELDX) and then a 5 shot group with factory ammo of 1.75", all at 200 yards.
After that, the wind picked up and I headed back to work, but I'm really happy that I seem to be on the right track with this rifle. I hope to get back out Sunday afternoon for another shooting session if the weather allows. Either that or I'm going to start building an ark....
Thanks to all of you that offered good advice. I definitely learned a lot here. I'm not going to win any bench rest competitions anytime soon, but at least I have confidence in this rifle and can move forward with load development and practice.
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Joined: Feb 2008
Posts: 1,168
Campfire Regular
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OP
Campfire Regular
Joined: Feb 2008
Posts: 1,168 |
Horizontal spread could indicate an issue with the rear bag. Definitely going to check into that. MD said something earlier about the sling studs and I'm pretty sure my rear sling stud was on my rear bag, so I'm going to change my setup next time out. That right there explains it. I always remove them for load development. If I had to place a bet right now, I'm going to say that the sling studs or something about my rear bag placement was the problem. I used to shoot better groups 10 years ago without even using a rear bag than what I was seeing with this gun last month.
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Joined: Nov 2008
Posts: 8,704 Likes: 2
Campfire Outfitter
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Campfire Outfitter
Joined: Nov 2008
Posts: 8,704 Likes: 2 |
Nice it’s working for you. Doubt you really fixed anything but rather discovered that small things at the bench can make big changes down range. Also I have never found a sling or swivel stud that sandbags ever liked.
Swifty
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Joined: Sep 2010
Posts: 19,179
Campfire Ranger
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Campfire Ranger
Joined: Sep 2010
Posts: 19,179 |
Congrats. The cloud is gone.
Happy shootin ....
Jerry
jwall- *** 3100 guy***
A Flat Trajectory is Never a Handicap
Speed is Trajectory's Friend !!
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Joined: Jul 2001
Posts: 60,202 Likes: 25
Campfire Kahuna
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Campfire Kahuna
Joined: Jul 2001
Posts: 60,202 Likes: 25 |
“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
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