Can't Zero at 25 Yds

[touji]

Hi all - 

 

I'm at work and contemplating an issue I had yesterday. I tried to zero my open gun at 25 yards (CK Arms Hardcore, 9mm major, Leupold DPP). It seems that at 25 yards, the gun is shooting way left (edge of the C/D zone with a center A zone hold over), but is putting together really tight groups at 10-15 yards at POA/POI. I tried cranking the windage adjustment of the DPP at 25 yards but it seems to only help moderately, so I stopped messing with the optic as it could definitely be a different cause. 

 

Does this jump out to someone as an easy fix / common cause? Optics, Ammo, Optic Mount, Comp, etc.? Any help would be appreciated!

 

 

[Sarge]

If it's right on at 15 and "cranking" windage didn't help at 25, I'd say it's the shooter and not the gun. Have another good shooter shoot it to see what it does.

[touji]

Just now, Sarge said:

If it's right on at 15 and "cranking" windage didn't help at 25, I'd say it's the shooter and not the gun. Have another good shooter shoot it to see what it does.

 

Will do! I was zeroing as I did my Carry Optics guns (off a sandbag) and I've never had this issue before. There are a lot more working parts with the CK that I was thinking it might be something simple I am overlooking. That might be the simplest

[Sarge]

1 minute ago, touji said:

 

Will do! I was zeroing as I did my Carry Optics guns (off a sandbag) and I've never had this issue before. There are a lot more working parts with the CK that I was thinking it might be something simple I am overlooking. That might be the simplest

Always easier to verify it's not you before looking too hard. I'm not saying it's you, but ruling that out.......

[touji]

Just now, Sarge said:

Always easier to verify it's not you before looking too hard. I'm not saying it's you, but ruling that out.......

 

Agreed, process of elimination is always best to pinpoint issues! I'll try heading to the range in the next couple of days and see if I can get one of my buddies out to the range with me. 

[echotango]

Also be sure that you are not getting a light bullet strike on the comp.  Typically would not group at 10yrds either, but worth a quick look. 

[kujo929]

I have this issue currently with a custom build tanfoglio open gun. Was getting rub marks on the comp so it was clear the comp wasn’t threaded directly straight or had not been alignment reamed. After the alignment ream it lessened the issue by a large margin.

 

I have 2 guns set up the same so it was pretty easy to confirm the issue in my case as I can swap parts and see what works and what doesn’t.

 

I wanted to believe I was doing something wrong and it was not the gun but after a lot of frustration it turned out that way.

 

Even after getting it reamed it still has some shift so it is fine for most Uspsa distances but I don’t use it in matches that I know will have 40+ yard shots or I have to hold completely off the target to get hits.

 

I’m going to pull the comp next and see if it is the barrel or comp that is threaded incorrectly. Hopefully it’s the comp so I can just get another on there and be good.

 

 

Sent from my iPhone using Tapatalk

 

 

[ChuckS]

If the sight is rotated off the horizontal bore line, it will only be "zeroed" at one distance. 6" difference between 15 yards and 25 yards would be the result of the sight being off by less than one degree. Shoot the gun (use a rest) and see what happens to the POI vs POA as a function of distance.

[theWacoKid]

1 hour ago, ChuckS said:

If the sight is rotated off the horizontal bore line, it will only be "zeroed" at one distance. 6" difference between 15 yards and 25 yards would be the result of the sight being off by less than one degree. Shoot the gun (use a rest) and see what happens to the POI vs POA as a function of distance.

 

Dew whuut?

[Sarge]

1 hour ago, theWacoKid said:

 

Dew whuut?

I know right? 

[Hi-Power Jack]

I had a similar problem many years ago, and it was the grip screw had loosened

and was changing the POI.

 

I think what Chuck S is saying (not sure, just my guess) is that if you have a

horizontal mount, this is possible - guess, so    ….    

[theWacoKid]

37 minutes ago, Hi-Power Jack said:

I think what Chuck S is saying (not sure, just my guess) is that if you have a

horizontal mount, this is possible - guess, so    ….    

 

No, still not possible.  A 1 degree angle in the horizontal plane of line of bore to line of sight (through red dot) would indeed change a zeroed poi at 15 yards to 6" off at 25 yards.  However, in order to achieve 1 degree angle between the two (if zeroed at 15 yards) the horizontal offset of the dot to the bore would have to be 9".  Haven't quite seen a setup like that yet.

Edited June 6, 2018 by theWacoKid

[ChuckS]

2 hours ago, theWacoKid said:

 

No, still not possible.  A 1 degree angle in the horizontal plane of line of bore to line of sight (through red dot) would indeed change a zeroed poi at 15 yards to 6" off at 25 yards.  However, in order to achieve 1 degree angle between the two (if zeroed at 15 yards) the horizontal offset of the dot to the bore would have to be 9".  Haven't quite seen a setup like that yet.

Yup, stumbled over my trig functions and geometry of the problem . Just push that crap aside and shoot from the rest and measure the horizontal difference in POI at 25 15 and 5 yards. If it is left - center - right  then the scope is biased to the right.

[Broncman]

I never zero my pistol from a rest because I never shoot from a rest.

Everytime I tried, it induced weird recoil that would be different from my shooting grip.

 

[BiggMike]

10 hours ago, echotango said:

Also be sure that you are not getting a light bullet strike on the comp.  Typically would not group at 10yrds either, but worth a quick look. 

+1. Once you rule out the trigger man, this is a good place to start.

[kujo929]

+1. Once you rule out the trigger man, this is a good place to start.

Not always the case though. When mine was striking comp it would still group extremely well. I guessing it just depends on how much strike you are getting.


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[OdinIII]

I know nothing of Open pistol optics but I did figure out a problem with a .22 rifle I had years ago. The scope had a 200 yard parallax adjustment and I couldn’t duplicate results from day to day. It would group but not in the same spot. I had about 3” of parallax at 40 yards IIRC.

Is it possible that parallax is your problem?

[touji]

Thanks for the replies, everyone. I don't think I should be having any parallax issues since I've used the same optic on my SP-01 when I was shooting Carry Optics

 

I will be looking to hit the range this weekend. I'll also try the following in order to try to rule out some things:

 

• Make sure all optic mount screws are tight
• Get some friends to shoot at 25 yards to see if it's a me problem
• Adjust DPP's windage to be POA/POI at 25 yards and compare POI at 7/10/15/20 yds
• Check to see if there is Comp striking

I may also try letting out the OAL on my reloads a little bit to see if I can get some tighter groups overall... but this could be a discussion at a much later time and for another forum!

[ChuckS]

1 minute ago, touji said:

Thanks for the replies, everyone. I don't think I should be having any parallax issues since I've used the same optic on my SP-01 when I was shooting Carry Optics

 

I will be looking to hit the range this weekend. I'll also try the following in order to try to rule out some things:

 

• Make sure all optic mount screws are tight
• Get some friends to shoot at 25 yards to see if it's a me problem
• Adjust DPP's windage to be POA/POI at 25 yards and compare POI at 7/10/15/20 yds
• Check to see if there is Comp striking

I may also try letting out the OAL on my reloads a little bit to see if I can get some tighter groups overall... but this could be a discussion at a much later time and for another forum!

Plunk test the ammo if you make it longer