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Old January 26, 2012, 03:09 PM   #1
300magman
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Odd Occurrance or Happens All The Time?

I haven't owned many rifles that didn't immediately get scoped, so a recent issue with my open sight 45/70 has me wondering if I have stumbled onto something unusual.

Factory Ammo required the sight adjustment ramp be used on close to the middle notch, various handloads had me adjusting up or down a notch or so, but nothing major.
Then my must recent loading (a 300gr JHP @ 2100) went flying off to points unknown when shot at my 100 yard target...after moving up to 25 yards my shots began to just hit the top of the target. Well, even after moving the sight ramp to its maximum position to try to get the shots on target, I find myself still shooting almost 1 full foot high at 50 yards with this load.

So....is that odd, or do some loads just come with large shifts in POI?
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Old January 26, 2012, 03:11 PM   #2
FrankenMauser
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Some loads can definitely show massive shifts in POI. But what you describe with your most recent load sounds like something else is going on.
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Old January 26, 2012, 03:29 PM   #3
mrawesome22
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If they are low velocity, they will hit high.

They call it dwell time. The bullet is in the barrel longer, therefore the muzzle has risen farther by the time the bullet exits.

Are they low velocity loads?
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Old January 26, 2012, 10:44 PM   #4
300magman
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mrawesome22 - for a 45/70, my load is very light weight and high velocity.
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Old January 26, 2012, 11:45 PM   #5
dacaur
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ive seen it. my brothers marlin 30-30. We were sighting it in, and got the scope pretty well dialed with 150gr reloads he bought. THen we tried some factory leverevolution loads, POI was about 3 inches down and 8 inches left... tried more of the reloads and it was back to center hits...

As for your situation, lighter bullets or higher velocity will cause POI to shift higher.... so it goes to reason that higher velocity AND lighter bullets will hit MUCH higher....
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Old January 27, 2012, 12:53 PM   #6
totaldla
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Your shots were going high and you moved the rear sight ramp up? Backwards.

Anyways, it is a common occurrence. I have this issue with both my M336 30-30 and Guide Gun. I don't understand the barrel dynamics involved, but I have to move the rear peep sight way up when I'm shooting plinkers at 25yds. I've etched the settings into the WRGS.
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Old January 28, 2012, 02:23 AM   #7
bbqncigars
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That much POI shift is not unexpected when going to a bullet that light (relatively). A normal bullet for the 45-70 is more like 400+grains. I feed my Marlin lever action 405gr LFN boolits whilst the Sharps uses 515gr custom boolits. The Marlin load shoots high in the Sharps at 100yds, but the Marlin won't safely chamber the heavier boolits.
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Old January 28, 2012, 03:53 AM   #8
mrawesome22
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If you had your gun sighted in with a slow bullet with a ton of drop, the lighter, flatter shooting rounds will shoot higher.

Sounds like everything is as it should be.
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