.243 Zero Shifting?

[wilbert 6]

Just a quick follow up to this little problem. i have just been giving the rifle a quick clean with a dry patch and removing the mod, no brush and solvent. Rifle has held its zero fine and I have had no misses. i have been eliminating all the possible causes 1 by 1 and now the only thing i hve not done it give the rifle a full clean. i have attached a pic of a group of 3 shots at 150yds on air rifle target. The first shot was a little high as i had just run 300 yds to re position the target (not best practice i know but the mist was coming down fast and i didn't want to miss the window of opertunity) and my heart was beating a little faster than normal. Anyway i am still happy with the group and it should be good enough to pas the DSC1 when i take it later in the year unless the nerves kick in!!!

 

[dadioles 68]

The only way to sort out problems is slowly and methodically, checking one thing at a time and then moving to the next.

 

When you shoot a fox you don't really know where the bullet has hit relative to a target, it could be different by 6" and you would not know.

 

It is quite normal for your zero point to change quite considerably mod on or mod off because of the weight of the mod and / or barrel harmonics. The size of the group should not change, it should shoot just as accurately, only the position on the target "the zero point" may change.

 

I have suggested testing your cleaning regime at the end of this experiment. I am one of the "clean thoroughly - rod and patch" brigade, but opinions differ and a lot of people shoot accurately without cleaning.

 

If I was in your shoes, and bearing in mind that ammunition is expensive, I would ...

 

1. Fire three shots with the moderator on aiming exactly at the centre of the target. Do not make any changes to the scope or anything else. It does not matter if the bullet holes are an inch or two from the aiming point. That will be sorted out later, all we want is to see how it groups.

 

2. Remove the moderator - do not make any other changes. Now fire three shots (a fresh target may be a good idea) again aiming at the centre of the target. The bullet holes may be in a different place to your first target (barrel harmonics or whatever) but the group should be a similar size.

 

3. Put the moderator back on and fire three shots at the centre of a new target. They should form a group almost exactly as in the first target, same group size, same position on the target.

 

If all three groups were reasonably tight, it suggests that your ammunition choice is sensible and you are shooting quite well and the moderator is not causing any problems.

If the group size is different with moderator on compared with moderator off it suggests that the moderator is having an effect on the accuracy of the gun, it should not affect accuracy, only the zero point.

 

Assuming you are happy with all three groups, you have eliminated the moderator as a problem and can now make whatever scope adjustments (if any) that you need to make sure that the gun is shooting zero with the moderator on. You will always shoot with the moderator on.

 

Ideally, when zeroed, your horizontal and vertical scope turrets will be adjusted to somewhere near their central position. If they are anywhere near their extremes you will need to shim the scope. When fitting a new scope it is a good idea to rotate the turrets to one extreme until it stops, then all the way back, counting the clicks, until it stops again, then half way back again so you know it is in the centre.

Left and right adjustment should not be too much of a problem unless your gun has been sloppily built or your scope mounts are misaligned as everything should be in a straight line, more or less.

Vertical adjustment is something else and may require a shim (cut a piece of aluminium from a coke can or use old photographic negatives).

 

Hopefully, you now have a gun that shoots an accurate zero with the moderator on.

 

Use the gun for a couple of days - do not clean the barrel! We are trying to eliminate the variables one at a time and cleaning would confuse things. The only thing you should do to the rifle is remove the moderator before it goes into the cabinet and refit the moderator before the next shoot.

 

After a couple of days, or whatever, take three more shots at a target exactly as with our first test, moderator on, aiming at the centre.

 

Hopefully (lots of hopefully's), the shots will form a satisfactory group around the centre. If they do not, there could still be a moderator problem but it is unlikely.

 

The scope and mounts (particularly the scope) would be the next thing to check and unfortunately it really means swapping the scope for another one to see if the problem goes away when a different scope is fitted.

 

Finally, you could "test" the affect of cleaning.

 

I am assuming that the gun is shooting accurately, your scope is setup for a good zero and all is well, you are a happy shooter.

 

Its back to three shots at the target with a dirty gun - hopefully all tightly grouped near the centre.

 

Now clean the gun really thoroughly and I mean obsessively clean, rod, patches, copper remover, the lot. You are seeking perfection and it does not come quickly.

 

For your final couple of patches moisten one with a drop of meths to remove any remaining oil or chemicals and then lastly a dry patch.

 

Now three shots at the target again, exactly as before.

 

The first shot may be a little off (not much) and the next two, with luck, back where they should be.

 

If these first few shots after that really thorough cleaning fail to group, fire a few more to see if it tightens up.

 

I am hoping that the groups will be tight straight away, if not, it suggests that your gun shoots better dirty.

 

Do let us know how you get on.

[charlie caller 3,654]

Just carry on as you are now, I told you it was down to cleaning when you decide you want to clean it, just remember to put some fouling rounds down the bore after and it will be back on song, just leave it 60 or so rounds between cleaning it, or more if you are feeling brave.