Sighting in rifle

[Mccabe]

Hello, I’ve never had a issue before I’ve developed a load for my .300 ultra I’m using retumbo powder 84 grains I’m using Barnes 190 LRX I sighted my rifle in at 100 yards 1/2 inch group I went to 200 yards which should shoot a inch low I have a 1/4 inch group but I’m six inches low I should have to make any adjustments . Any ideas thanks tucker 


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[Mccabe]

Here is the groups


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[Jolten]

How are you calculating you should be an inch lower? Ballistic calculator? Did you verify your speed?

[Mccabe]

I don’t have a chronograph. Im just going off the box as if I use factory loads it says at 100 yards you should be 1inch high and 200 yards you should be dead on


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[Jolten]

Box speeds don't work for reloads. What's your reloading manual say 84gr should get you?

[Mccabe]

It says at 86 grains the velocity would be at 2950 . Which I’m using 84 grains. The factory loads is 3125 velocity .


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[Taco280AI]

It doesn't matter what the factory ammo says, you're not using factory ammo. Guessing you're at 2900fps with your 84 grains, that should get you about 3 inches low at 200 with a 100 zero (without knowing all the variables).

Get a chrono. Or shoot at 200, 300, 400, 500... and find your actual trajectory then calculate your velocity off that.

Or it could be something you're doing differently with your shooting form at 200 vs 100. Parallax? Lots of unknowns 

[Mccabe]

Thanks I think I’m going to make 200 yards my zero and sight it in for that . And go from there I’ll be hunting goats in the olympics which more than likely will be a longer shot


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[Shadrach71]

Yeah way to many variables in this equation. As stated above you need to verify speed over a chrono to even begin to know part of the equation, then take it out to verified distances (200, 300, 400, 500 yards ect) so you can verify drops. Then enjoy your hunt and learn windage if shooting longer distances. Good luck on the goat hunt 🍻

[Magnum_Willys]

You are right something strange is happening - you change something other than distance from 100 to 200 ?   

[JimmyHoffa]

Scope height?

[Jolten]

25.0   2907.2   1.10   4.14   0.0
50.0   2864.5   0.47   0.87   0.0
75.0   2822.2   0.08   0.12   0.0
100.0   2780.2   0.00   0.00   0.0
125.0   2738.8   0.20   0.14   0.0
150.0   2697.5   0.67   0.43   0.0
175.0   2656.8   1.46   0.79   0.0
200.0   2616.5   2.52   1.21   0.0
225.0   2576.8   3.94   1.67   0.0

My calculator says he should be just over 2.5" low at 200 at box speeds. I'm wondering maybe scope is loose, or canted.

[Jolten]

Only way I can get muzzle velocity to match his 6inch drop is to drop it to 2200. Which seems way too low for 86gr

[Mccabe]

I never changed anything from going from 100 yards to 200 yards . My scope height is 1 5/8 it’s nice and tight.


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[mazama]

Moving the position of your rest,or head or moving target at different to different angle,i used a pillow one time because I forgot my rest that changed my impact 3 inches.

[blackpowderhunter]

i'd borrow a chronograph.
not saying your vel. is 2200 fps as calcs would suggest, but its hard to guess around velocity.
some barrels like something more than another, could be a funny batch of powder, whole bunch of stuff.
the weird part is that whatever velocity you're getting, they're grouping nicely 

[buckfvr]

If you arent able to collect actual velocity data, you probably arent going to be able to resolve your issue.  In that case you may be well advised to buy a couple boxes of factory ammo for sight in and hunt until you have a chance to resolve the issues.  If the factory ammo does the same thing then you have other problems to resolve.   

[Mccabe]

Thanks I never had a issue before with factory ammo, just haven’t found any for over a year and half I have a custom cds dial for that specific ammo not sure if it would throw it off using different ammo with that cds dial .


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[buckfvr]

If the velocity data you used for the dials doesnt match collected data from your handloads, you will be off your mark.  If your dials were cut from "box" data from your factory ammo, you may have the same problem, however if its close enough it wont show that much until 500 yards or more.

Ill add, yes, I have had CDS dials and have tested 2 rifles that both had them out to 650 yards.

[Damnimissed]

FWIW, that is an extremely mild load for RUM. I don’t know anyone running under 90gr of Retumbo. I’m pushing 200gr AccuBonds at 3135fps with 92gr of Retumbo with no real pressure.

[Mccabe]

I was just going off the Barnes load data it showed 86 grains as max, I called and talked to customer service he did say I can up it a bit just watch pressures . I did try 86 grains It just isn’t grouping like I am at 84 grains.


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[Bushcraft]

No offense intended, but how much experience do you have with handloading?  Everyone starts somewhere. It's good that you are asking questions.  I recommend stopping what you're doing and asking a lot more questions.