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October 30, 2010, 02:18 PM | #1 |
Junior Member
Join Date: September 20, 2010
Posts: 8
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Sighting Question for 870/Mossberg DRS
I test fired some slugs at the range today with my 870 express, which has a new Mossberg slug barrel with deer rifle sights. A few slugs grouped well, especially copper solids, but at 25 yards, all slugs were at least 4" high. The copper solids are supposed to zero at 50 yards and be only 1/4"high at 25 yards.
Even with my rear sight "bottomed out" for elevation, I am still too high with all the slugs. Am I correct that I should be lowering my rear sight to lower my point of impact? If so, where to I go from here? Thanks, CV |
October 30, 2010, 04:08 PM | #2 |
Staff In Memoriam
Join Date: October 31, 2007
Location: Western Florida panhandle
Posts: 11,069
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Yes you lower the rear sight to drop the point of impact.
I would put the rear sight at about mid way and check it at 100yds, then 80 then 60 then 40... I would then make a decision regarding adjustment. The "supposed ta' " doesn't take into account, the rear stock design, the way you weld your cheek nor the size of your head... Just a starting point... Brent |
October 30, 2010, 05:36 PM | #3 |
Senior Member
Join Date: August 23, 2008
Location: SoCal
Posts: 6,442
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Raise the front sight, or remove some material from the top of your rear sight to lower your POI (point of impact). But, only after following Brent's recommendation for incremental verification
Remember, the slug's trajectory crosses the aim line twice. The height of the sights above the bore plays a major factor in determining at what distances the cross points occur. An old rifleman's trick is to mount their sights high to increase their point blank* range. It's one of the reasons modern battle rifles have higher sights than they did back in the day. *point blank: The range where your POA (point of aim) and POI are close enough to insure a kill without adjusting your sights or holding high or low. |
October 30, 2010, 07:14 PM | #4 |
Junior Member
Join Date: September 20, 2010
Posts: 8
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Thanks very much. This is exactly the info I was looking for.
I was considering taking some material off the rear sight, as the front sight is adjustable only for windage, not elevation. Of course the idea of smithing my sight is little intimidating. After reading your posts, I realize that I'm not at that point yet, and that I need to get some more slugs and do some incremental testing at longer ranges. The idea of high sights to increase PBR is interesting. That seems to be how my sights are configured. Back to the range! CV |
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