Scope Causing Accuracy Problems?

[J_idaho]

I wanted to post a recent scope issue I’ve been having that is a bit odd. This was a very hard thing to diagnose and I pretty much just stumbled across it since despite the size of groups the scope still tracked.

Rifle is a CA mesa in 300wm



My problems started several rounds after buying a Arken scope for my sons 243win and I ordered to tall of bases making it hard for him to shoot.I hadn’t purchased a cheek riser at that time. So I traded him with my nightforce which had much lower mounts. The Arken rings were 34mm and the nightforce are 30mm. I actually liked the scope and had no problems until recently when my groups and poi was not right.
So a long story short I discovered that the bedding job was loose and there was a crack running through the stock between the mag well and trigger well. So I thought this has to be the problem. I fixed everything and re bedded the stock. “FYI” CA said they would fix the stock but I didn’t want to wait.
I went out and shot again and I could tell that the poi was much more precise but the groups were still a train wreck this is when the scope really began to be in question.

So I went out today and swapped scopes from my sons 243 and his gun shot same as always. And my gun shot back to the way it used to shoot.

That’s when I decided to just set the zero stop and use them as is until something breaks I can’t send a scope back if it’s not acting up. After setting zero on the 243 with Arken scope. I shot this group.



This was an eye opener for sure. So I loosened the zero stop and set it several mils below zero “ meaning I kept zero as zero but just moved the stop because there seams to be a certain amount of tension those last few clicks before reaching zero. Then I shot this group.

]

I know this is just a three shot group but I was out of time and frozen to the bone.
I’m pretty well convinced that this is the problem. I will probably contact Arken and ask if I’m doing something wrong or if they recommend anything short of sending it in. I will avoid that for now. I’ll be glad to do an update in the future if I figure out that I’m wrong.

 

[ShtrRdy]

I didn't read the whole post so please forgive me if you covered this. Were you able to try a different, known good, scope?

 

[Forum Boss]

Scopes CAN cause accuracy issues (from reticles that are not stable etc.), but the images you posted don't really tell me anything definitive.

 

[Prose]

So turning the scope down to the zero stop was causing the issue? I.e. As long as you didn’t have it leaning against that it shot well? That is certainly interesting.

 

[fkimble@charter.net]

I would not use a zero stop for my bottom setting. I would put the stop a minute or so low. Go down to the stop and then back up a minute. Hitting the stop and leaving it there "loads" the threads putting stress on them. Main use of the stop is to prevent getting a full revolution off and not knowing it.

Frank

 

[Eagle Six]

I think you are headed in the right direction. As Frank stated stay off the zero stop, contact Arken and send it in if they feel it needs to be looked at. Not all zero stops on all scopes load the turrets, but I have also avoided my zero being on the zero stop regardless of the scope I'm using as a general practice.

 

[J_idaho]

Here are pics of just the 300wm groups with nightforce scope and the old groups with the Arken scope. I realize how bad I am at posting so I wanted to try and isolate the difference. The only reason for posting this is to show the size and shape of groups to help others figure out there problems.
pic#1___ 300wm with Arken scope "only groups highlighted" you can see that there is one small group but mostly everything is way off and its interesting how symmetrical the groups look.
pic#2 & pic#3___ "only groups highlighted" 300wm with Nightforce scope. You can see groups are all under .7" I only shot 13 rounds of 300wm and some of those missed the target because I didn't want to adjust the scopes but there was 20moa difference so i had to use the top of reticle for aiming. The only poi shifts are from me trying zero rifle I forgot i was using a 2nd focal plane scope at half power and my adjustments weren't correct.

 

[ShtrRdy]

How do I tell which groups belong to what?

 

[J_idaho]

How do I tell which groups belong to what?

It’s just the highlighted groups from SubMOA app. Anything not marked was either old shots or me adjusting for a zero. That’s why I didn’t mark an aim point on anything. You can see all groups in first pic are mostly huge with one small random group. After swapping scopes everything went back to normal .5-.7moa size groups

 

[Steveb]

I shot a lot of F-Class matches and I have found this to happen in most makes of scopes from cheap scopes up to very high-end scopes. The best explanation I can come up with it that the erector systems wear out and the tolerances become loose. I have asked several optical engineers from various companies why this happens, and none have been able to supply an answer. It becomes a "warranty???" issue because the scopes aren't accurate and that can be proven and replicated but nothing is rattling or broken so the companies question why you are sending in the scopes. I asked been asked why I am sending in the scope because it can still group and hit paper!!! I have also asked how many shots can the scopes take before sending then in for a rebuild and got no answer. I have also asked if various companies would offer a charged (paid) rebuild program so after, say 5000 rounds, the scopes can be sent in and have the erectors systems replaced to no avail. Unfortunately, no company has offered to do that.
It has come down for me to use scopes for a period of time then replace them. So every couple of years I get new scopes. Right now I am replacing my Sightron's because my 1/4 MOA clicks are giving me 3/4 moa adjustments. Prior to that I went through 5 March 10 x 60's!

 

[J_idaho]

It has come down for me to use scopes for a period of time then replace them. So every couple of years I get new scopes. Right now I am replacing my Sightron's because my 1/4 MOA clicks are giving me 3/4 moa adjustments. Prior to that I went through 5 March 10 x 60's!

That's some good info thanks for your input that makes perfect since. I wonder how many barrels "wear out" because the scope died and the person shooting it didn't realize it. I bet at least half or more of most peoples accuracy issues could fall under scope issues or lack of understanding. Just the ability to aim small with a high power scope vs using a fat reticle or low magnification scope. You can't shoot groups smaller than you can see. And I'm sure that anything with parts as small and precise as a scope are machined out of very soft steel or alloy to allow for fast production and then we strap them to a jackhammer and think there going to stay in perfect shape. years back i made a mount for my camera to attach to my rifle it only lasted a few months and the recoil destroyed the camera. I do wonder why we don't hear more people talking about this stuff i suppose since it is a very competitive game out there and scope makers are not going to tell you that your $2000.00 scope is not going to last more than a couple years under heavy use. Well thanks for the comment I've only heard of the grease in scopes drying up over time especially if there not being used.

 

[Steveb]

I have gotten to the point where if I am having accuracy issues with a known rifle the first thing I do is change the scope.
Speaking of soft parts, I once deformed the elevation adjustment slot on a Leupold Vari-2 simply by twisting a coin in the adjustment slot. I didn't bottom out just simply turned it and the material was so soft it mushed out.

 

[JEFFPPC]

Did you always use flags? If not targets are worthless. If you are, put a known good scope on, easiest way to check.

 

[Steveb]

Always use flags and always test repeatedly over a number of days to confirm fault isn't in the shooter. Always keep a box or 2 of of "confirmation" loads of known accuracy for powder lot checks too and to diagnose other issues.

 

[Litespeed]

Did you verify your parallax? My brother found his Arken to be very sensitive and just because the targets were in focus didn't mean the parallax was set correctly.

 

[Steveb]

This is a common problem I have found across many makes of scopes regardless of cost of the scopes. It is not isolated to one brand or scope. Also, it is not isolated to myself. That is why I change scopes regardless of brands and have developed a protocol and supplies just in case. It has saved me a lot of grief and supplies over the years.
I have come to accept that scopes are like barrels. They wear out after a being on rifles that have shot a large number of rounds. What I have been unable to determine is how many rounds does this take and when should I replace them.

 

[J_idaho]

Did you always use flags? If not targets are worthless. If you are, put a known good scope on, easiest way to check.

No just some ribbons to try and time the wind but it would take a typhoon to move groups as much as I was seeing. And the groups were moving the opposite direction of the wind.

 

[J_idaho]

Did you verify your parallax? My brother found his Arken to be very sensitive and just because the targets were in focus didn't mean the parallax was set correctly.

Yes I do believe it is always set as close I can get it. If you look at the pictures you can see that the groups are all over the place. But if you look at how square shaped some of the groups are they just have a sort of mechanical look to them. I was measuring one of the groups and it is within .01 in relation to the bullet holes only close to an inch apart. If it was just me you would see groups more dispersed.

 

[JEFFPPC]

No just some ribbons to try and time the wind but it would take a typhoon to move groups as much as I was seeing. And the groups were moving the opposite direction of the wind.

Hey ribbons are fine. Light years beyond nothing. Good.

 

[tactserv]

Disclaimer : I am new to bench rest shooting, learning free recoil. Up until now my scope shooting has always included a good cheek weld, resulting in line of sight through the center of the scope. Little to no parallax errors. When I started bench rest, my scope was/is in high rings to avoid contact with the stock. No cheek weld meant I was all over the place when looking through the scope, much parallax error, and hits all over the target.
You mentioned you changed to tall rings at the time you started having issues. Maybe same cause?