Resetting my scope - any tips?

[neutron619]

If this is in the wrong section, apologies - perhaps one of the mods could move it?

I went to a range to today and have been struggling to understand the results I've seen with the rounds I was testing.

I was testing three different reloads for safety and to find powder maxima for them, but through the course of the day, I saw evidence of canting errors in my shooting. The fastest of the reloads shot high and to the right. The middle one for which my rifle is currently zeroed shot correctly in the middle and the slower, heavy load shot down and to the left. My horizontal point of aim was always the same (i.e. the vertical line running through the bullseye), however.

I didn't twig about this until I got home, but that diagonal line across the target is most likely caused by canting the rifle clockwise (from the shooter's perspective) and, sure enough, when I just took the gun out of the cabinet to look at it, the scope is misaligned slightly in the counter-clockwise direction (again, shooter's perspective). This means that I was turning the gun off-vertical to get the scope vertical line to appear, well, vertical.

The net result is that I need to reset the position of my scope so that the vertical scope line runs perpendicular to the rifle's bore.

I'll do this, but I'm aware that it could have been mis-set for some time and that I probably created the error in the first place by not mounting the scope in the proper alignment. I doubt the scope has slipped in the mounts - they've held fairly well if my usual load and it's basically static zero is to be believed.

Therefore I'm after suggestions: when I'm resetting the scope, how can I best ensure that the rifle is correctly aligned, vertically, and then match the vertical axis of the scope to it, so that I don't end up simply setting a different misalignment and canting the rifle in some other way? Any techniques / tips will be very welcome.

I'm aware I'll need to re-zero each of my loads when this is done. Are there any other consequences of resetting my scope that I haven't thought of?

Many thanks,

Adam.

 

[AN DU RU FOX]

Im not saying this is the correct way but i put my rifle in my vice/rest ?spirit level on the top of rail level it lock off the rifle then place bases on then scope, remove scope cap and place level on that start to tighten everything up slowly and keep checking the level till tight,

 

[Gaothead]

From my limited experience:

The zero walks up and across as the load is increased. When it doesn't move much that is the sweet spot which is less sensitive to load and will give be most consistent accuracy. This is separate to the cant you have observed.

To align scope with rifle I eyeball the vertical of the cross-hair with the centre of the bore. If your constant then cant doesn't matter that much but you can only zero it out at one range. Then I expect more of a problem if you use milldots for holdover. A bit of cant can not matter much at normal deer ranges.

 

[countrryboy]

Agree with the above and doubt at normal ranges will make much difference

If it has been off since u put the scope on it can't really be affecting u that much, once u zero ur scope its still shooting accurately.

Wot i tend to do is prop my rifle up aiming at a straight line (corner of room, walls to ceiling or work top/cupboards etc) so in theory should give u a stright line, ideally if u can eye ur rifle up to a vertical line and level cross hairs to a horizontal should give u 90 degrees, but as i said i'm not overly fussy

 

[shuggie]

Hi Adam try using a plumb line or draw a line on paper horizontal and vertical way a level ,when testing different loads you change the harmonics of the barrel which can change the point of impact ,more so if its a sporting barrel good luck

 

[neutron619]

Hello Chaps,

Thank you for the suggestions, much appreciated.

I'm aware that point of impact will change with different loads, but I still think there's a problem that needs solving here. A reasonably consistent, 1" @ 100m reload was dropping 7" (as opposed to 3-4") at 180m and was over 3" further to the left than I expected. The misalignment of the scope is noticeable (or it is, now I've noticed it) and isn't just a degree or so - it's between 5 and 15 degrees off, I'd say - so there is a significant effect and a significant error.

Usually, I'd expect some variation across both axes because of my standard of shooting and because of the trajectory I'd expect of the reloads (i.e. not great) but today I was taking shots I knew I ought to be able to make (i.e. standard deer target) and was ending up with gut shots and misses underneath rather than an upper front engine room hit.

Anyway - I'll probably bung it in a vice with a spirit level and a plumb line just to be on the safe side and see if I can't get it sorted out tomorrow evening.

Thanks again,

Adam.

 

[Crosshair243]

Hello Chaps,

Thank you for the suggestions, much appreciated.

I'm aware that point of impact will change with different loads, but I still think there's a problem that needs solving here. A reasonably consistent, 1" @ 100m reload was dropping 7" (as opposed to 3-4") at 180m and was over 3" further to the left than I expected. The misalignment of the scope is noticeable (or it is, now I've noticed it) and isn't just a degree or so - it's between 5 and 15 degrees off, I'd say - so there is a significant effect and a significant error.

Usually, I'd expect some variation across both axes because of my standard of shooting and because of the trajectory I'd expect of the reloads (i.e. not great) but today I was taking shots I knew I ought to be able to make (i.e. standard deer target) and was ending up with gut shots and misses underneath rather than an upper front engine room hit.

Anyway - I'll probably bung it in a vice with a spirit level and a plumb line just to be on the safe side and see if I can't get it sorted out tomorrow evening.

Thanks again,

Adam.

Can you post a piccy of it? If it's that bad- it should be really noticeable in a picture.

 

[BRYAN]

I am not sure that canted crosshair will walk your POI left-right if you are not altering the elevation turret.
If you are conciously canting the rifle to align with the target frame,you are probably doing so with all of your loads.
The reference point of the scope is the centre of crosshair.
I do know how confusing scope mounting problems can get,tying you in knots sometimes.
Good luck in sorting it.

 

[neutron619]

Can you post a piccy of it? If it's that bad- it should be really noticeable in a picture.

Possibly tomorrow. Will be difficult to get the gun out again this evening.

 

[shuggie]

Hi Adam i remember having load problems way a custom rifle ,i spent weeks trying different things, i was shooting in world champs,ended up changing barrel still the same ,it had been fitted way a brand new scope,so i never gave it a thought but that had been the problem all the time ,sent it back for repair,got it shooting well with in a day worth checking

 

[neutron619]

I am not sure that canted crosshair will walk your POI left-right if you are not altering the elevation turret.
If you are conciously canting the rifle to align with the target frame,you are probably doing so with all of your loads.
The reference point of the scope is the centre of crosshair.
I do know how confusing scope mounting problems can get,tying you in knots sometimes.
Good luck in sorting it.

No, agreed, if it was the same load every time then no, I'd have to alter the elevation turret as you say.

However, in this case I was testing 3 reloads - a 110gr, a 150gr and a 220gr round. With the rifle zeroed dead-on for the 150gr round at 100m and the same point of aim, I'd expect the 110gr round to be about 2-3" high at 100m and the 220gr round to be about 3-4" below the bullseye, but for all of them to be basically on the vertical line running through the bullseye. No actual change in scope elevation, but a change in trajectory which will have the same effect.

Rather than just variation along the vertical axis of the target, I'm seeing left-right shift as well, which suggests that I'm canting the gun, and that ties up with what I'm seeing in the relationship between scope and bore.

I'm just hoping that correcting the score orientation will fix it. If I've also got a misalignment on one of the other axes (i.e. the scope is pointing in a different direction to the barrel in more than one axis, that will be even more serious.

 

[BRYAN]

I think you must be be canting the gun then because left-right impact changes would not happen with velocity changes.
Some scopes,I believe are only a dot,ie no wires.
A change in trajectory would not cause left to right changes if the elevation turret is unchanged and distance to target is constant.
Gravity would only work in the vertical plane causing high or low impacts.

 

[bogtrotter]

Agree with the above and doubt at normal ranges will make much difference

If it has been off since u put the scope on it can't really be affecting u that much, once u zero ur scope its still shooting accurately.

Wot i tend to do is prop my rifle up aiming at a straight line (corner of room, walls to ceiling or work top/cupboards etc) so in theory should give u a stright line, ideally if u can eye ur rifle up to a vertical line and level cross hairs to a horizontal should give u 90 degrees, but as i said i'm not overly fussy

Exactly how I do it.

 

[bewsher500]

I was testing 3 reloads - a 110gr, a 150gr and a 220gr round. With the rifle zeroed dead-on for the 150gr round at 100m and the same point of aim, I'd expect the 110gr round to be about 2-3" high at 100m and the 220gr round to be about 3-4" below the bullseye, but for all of them to be basically on the vertical line running through the bullseye. No actual change in scope elevation, but a change in trajectory which will have the same effect.

major assumption
never happens that way IMO unless you are extremely lucky

your barrel unwinds like a corkscrew when the shot goes off
the bullet POI correlates to the exit point in this oscillation of the barrel

canted or not
if you maintain a fixed POA and he ammo is a consistent you will get a fixed POI

 

[palmer_mike]

major assumption
never happens that way IMO unless you are extremely lucky

your barrel unwinds like a corkscrew when the shot goes off
the bullet POI correlates to the exit point in this oscillation of the barrel

canted or not
if you maintain a fixed POA and he ammo is a consistent you will get a fixed POI

hit the nail on the head!

 

[Hedgehopper]

if you you want to be really anal about it, then have a look at this. Not sure it is worth it unless shooting over very long distances though.

 

[pinkfoot1]

major assumption
never happens that way IMO unless you are extremely lucky

your barrel unwinds like a corkscrew when the shot goes off
the bullet POI correlates to the exit point in this oscillation of the bar

canted or not
if you maintain a fixed POA and he ammo is a consistent you will get a fixed POI

My thoughts exactly!

 

[neutron619]

major assumption
never happens that way IMO unless you are extremely lucky

your barrel unwinds like a corkscrew when the shot goes off
the bullet POI correlates to the exit point in this oscillation of the barrel

canted or not
if you maintain a fixed POA and he ammo is a consistent you will get a fixed POI

Ok - so I reasoned that one out wrongly and picked the wrong example of the two I had to give you. Mea culpa.

If I said that I'd also shot the same round at two different distances and that the longer distance produced a downward and leftward shift in POI, I think you'd agree that that was a canting error?

I adjusted the scope last night and got it a bit straighter I think. Then the rifle fell over from where it was standing and I did it all again...

Anyway, it's probably not perfect, but it is an improvement I think.

As I hinted above, one of the other problems I was having at the range on Saturday is that the shift between the 100yd and 200yd line was turning a good central chest shot into a low gut shot. I was getting a both drop - more than I'd expect - and horizontal shift at the longer distance, so I wasn't happy - I certainly won't be pointing the rifle at a deer until I have it sorted, or at least, re-zeroed and much improved.

 

[Klenchblaize]

Try and get another suitably experienced shooter to have a look at your setup when next at the range. I’m not convinced your concerns are going to be answered/resolved on a Forum.

All the best

K

 

[User00001]

I think that you are trying to do to much at once and ending up in a pickle.

The scope needs to be correctly fitted regardless of load or range so get this sorted out first.

The three loads that you are testing are wildly different (110gn, 150gn and 220gn) don't worry about where they go in relation to each other, anything could happen. You might be lucky and find that the 110 and 150 are pretty close at 100m but I wouldn't count on it.

If I were you I would concentrate on one load, probably a general purpose 150gn, and get this shooting well before I even looked at the others. I have been in this situation of trying to develop two or three loads for one rifle at the same time and it can be time consuming, frustrating and confusing even after twenty years of reloading.