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Discussion Starter · #1 ·
So I’ve been trying to zero in my Eotech EXPS3-4 with G-33 3x magnifier on my Bushmaster XM-15, just when I think I’ve got it dead to rights at 50yds it starts shooting 2-3 inches left or right with no intervention whatsoever, completely repeatable too. I mean it’s still deadly accurate, I’m going to hit what I’m aiming at no problem but I wanted to get my grouping basically on top of each other. I thought it was maybe I’m just a crap shot or my optic is defective, but a buddy of mine said that it may have to do with the carbine length barrel and the fact that this rifle just isn’t designed for that kind of accuracy. Does anyone have any insight to the issue I’m having?
 

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S&W 637-2, M&P sheild 9mm
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Is the scope tight on the carbine? Have you tried different ammo types? Are you an accomplished shooter with other platforms?

Try another scope on the same carbine to rule out a possible problem with the eotech.
 

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Discussion Starter · #5 ·
Is the scope tight on the carbine? Have you tried different ammo types? Are you an accomplished shooter with other platforms?

Try another scope on the same carbine to rule out a possible problem with the eotech.
What’s weird is the cheap Chinese sight that came with it held a zero better which makes no sense because Eotech is supposed to be top tier stuff. I’ll have to play around more next time I go to the range. I’ve used lake city 62gr and Hornady Frontier 55gr and get the same result.
 

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A Torj
You could possibly have the intensity of the Dot turned up too bright. I have taught the L-3 EOTech LE Operator's Course for them in the past. You only want it so you can just make the Dot out when shooting for precise groups. One must understand the optic is made for CQB. If it is set too bright I would explain it as reticle (Dot) glare. It will cause a difference in your view of the target. So what you think is exactly on the exact spot on the Target in fact it is not.
And if you get the barrel hot as was mentioned some rifles will throw rounds off. It is a metallurgical issue. Picking the Fly Sh*t out of the Pepper some rifle barrels will change impact from the first round to the ones following. In the Sniper World we call that first shot the Cold Bore Shot. For example one Sniper Rifle I had would shoot 3 Rounds on top of each other at 100 yards but then the Barrel heated up and it would always throw the 4th Round 2" off. But as the others stated make sure your mount is tight.
*But with a cool Barrel a 16in. CAR Length gun should be always able to shoot group under 2 MOA (Inches) at 100 Yards. Most are capable of 1 MOA with good quality ammunition. Keep us informed if we can be any additional assistance.

03
 

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Yes with the thin barrel when it gets hot. It does a ''whipping motion''. And starts to throw flyers. My Mosin nagant does it too. I shoot a string of 5 rounds. Let it cool for 5 mins with the bolt open. Then shoot and repete.
 

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The only time this has happened to me when unbeknownst to me that optic was not tight.. and after some shots had been jostled into a slightly different spot touching on the picatinny.

I thought I was just exhausted and not shooting well anymore ( small steel targets.. I couldnt see that how it was wandering.. just noticed lack of pings).. had been shooting for 8 hours and it was hot...

Eventually i noticed it.. thought it was tight.. guess it wasnt...
 

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So I’ve been trying to zero in my Eotech EXPS3-4 with G-33 3x magnifier on my Bushmaster XM-15, just when I think I’ve got it dead to rights at 50yds it starts shooting 2-3 inches left or right with no intervention whatsoever, completely repeatable too. I mean it’s still deadly accurate, I’m going to hit what I’m aiming at no problem but I wanted to get my grouping basically on top of each other. I thought it was maybe I’m just a crap shot or my optic is defective, but a buddy of mine said that it may have to do with the carbine length barrel and the fact that this rifle just isn’t designed for that kind of accuracy. Does anyone have any insight to the issue I’m having?
First you should isolate the problem by shooting the gun with a different sighting system (a scope would be better because it will give you optimal accuracy to use as a benchmark). That way you'll know if it's the gun or the sight. THEN you can concentrate on finding a solution.
 

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Wambli
Has a good point if you have another quality optic to use on the gun. If the EOTech is tight and properly mounted that would settle the issue of the area of the problem. Gun / Scope /Ammunition?
Only a thought!
I know I am probably preaching to the Choir! But also be sure when you are shooting trigger placement is always the same and press. Trigger Finger in front of the First Joint on the Pad. Also that you are not torqueing the gun during shooting. One way to check this is to get on Target ready to shoot. And before you actually pull the trigger look at the Dot and Target. Then close your eye or eyes and open it or them and see where the Dot is.
If it stays the same we call it having the gun in a Natural Point of Aim. And not musceling it when shooting. Otherwise the Dot should remain exactly on target when the eye or eyes are opened. If it is off you are musceling the gun. Some times guys do it without noticing they are. This will certainly cause the point of impact to change when shooting. And of course breathing will do the same.

03
 
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Wambli
Has a good point if you have another quality optic to use on the gun. If the EOTech is tight and properly mounted that would settle the issue of the area of the problem. Gun / Scope /Ammunition?
Only a thought!
I know I am probably preaching to the Choir! But also be sure when you are shooting trigger placement is always the same and press. Trigger Finger in front of the First Joint on the Pad. Also that you are not torqueing the gun during shooting. One way to check this is to get on Target ready to shoot. And before you actually pull the trigger look at the Dot and Target. Then close your eye or eyes and open it or them and see where the Dot is.
If it stays the same we call it having the gun in a Natural Point of Aim. And not musceling it when shooting. Otherwise the Dot should remain exactly on target when the eye or eyes are opened. If it is off you are musceling the gun. Some times guys do it without noticing they are. This will certainly cause the point of impact to change when shooting. And of course breathing will do the same.

03
Well expressed. Shooting form is so often overlooked as a potential issue when chasing accuracy potential. I’ve see an experienced rifle shooter shoot groups HALF as big as a shooter with form flaws using the same rig and ammo.
 
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