Fairly long post, but please read it through.

Common causes include:

1. Scope - Self explanatory really. A faulty scope will "jump" with each shot, not track, etc.
2. Mounts - If they are not tight enough, misaligned, etc. they can cause issues with zeroing.
3. Ammo - Depending on twist rate and what your gun likes poor quality or just a "bad fit" ammo will cause zeroing issues. Solution is to try various brands/weights and see which works.
4. Suppressor - If the threading of the rifle is not done properly, or on the rare occasion the threading of the Mod is not correct, you will get a misaligned suppressor causing the ammo to clip the mod on leaving. This clipping can be so subtle you might not see it. A way to test is line the inside of the muzzle of the mod with tip-ex or something similar and when you fire a round check to see if there is mark or void in the tip-ex (or whatever you've used). If so you can try and bore out the mod or get the rifle re-threaded.
5. Stock - If the stock is touching the barreled action it can interfere with the barrel harmonics.
6. Crown - If the crown is damaged it will cause widening of the groups. It's a small area and unless you know what you're looking for you might not see a problem. Gunsmith can check and re-crown if necessary.

There are some things you can do to check the above.

1. Scope - If you had it on another rifle and it worked then grand, however a hmr is a different animal to a Swift so try the scope on another centrefire rifle. A mate's. Also a box test might be useful when on the other rifle.
2. Mounts - Check that the screws are tight and that the mounts are not shifting on the receiver/rail. Also check the scope is held in the mounts and not slipping in the rings.
3. Ammo - Try different brands, and different weights of ammo. See which performs the best.
4. Suppressor - Shoot the rifle with the mod off and see if the problem persists. If so the mod is the issue. If not then it's not the mod. Or not ONLY the mod. Bring to gunsmith to check/repair.
5. Stock - Slide a piece of folded paper up along the top of stock/bottom of barrel and it should be able to get to the front of the receiver/action without obstruction. If it sticks at any point then mark the stock and look at sanding the stock. If it's composite the same applies.
6. Crown - Bring to gunsmith.

Two big issues with scopes, new or second hand, is zero hold & tracking. Tracking refers to the scopes ability to be dialed in/adjusted, but return to a preset setting. For example your zero or to accurately and repeatedly move the exact amount you dial. Zero hold is self explanatory. The ability of your scope to maintain a preset zero without loosing it due to movement, etc.

Yoy need to test the scope. This can be very hard as a lot of factors can affect this. Factory ammo compared to handloads (inconsistencies with speed, etc), weather conditions (wind, etc), shooting position, etc, etc. There are a couple of tests if you fancy doing one or some.

Linear Test.

This is a simple test. Place a target (blank sheet of paper at least 48 inches tall and 24" wide) at a set distance with a single aim point/dot. With your scope mounted you take up a solid and stable shooting position. Have the gun as "clamped" as possible to avoid errors. Have the scope elevation set at 0 or bottomed out. Now dial up in increments of 5 or 10 MOA (or any amount you want) and fire a single shot after each adjustment.

You MUST keep the same point of aim throughout this test. Also use the same amount of adjustment each time until you run out of adjustment. ?When you have no adjustment left take the target down, and measure the distances between each bullet hole in the target. They should be equidistant. They should also be perfectly vertical. Any continuous left/right adjustment can be down to either poorly mounted scope (not perfectly aligned when mounted) or inability of the scope to track straight up and down. Do this once or twice to verify.

Return to Zero test

Simple test. With your scope mounted and rifle zeroed at 100 yards set yourself up much as above at a target. Fire 3 to 5 shots to create a zero group. Record the setting on the scope for your zero as you'll have to return to this. Now start to adjust the scope as much as you can (through it's entire range of adjustment) up, down, left, right and combinations of all. Now return the scope to the recorded zero. Fire a shot. It should be in or clipping the group you just fired. If not then it could be a scope tracking issue. As with all tests it's best to try it a few times to prevent corruption of the results from shooter error, wind, shooting position, etc.

Box Test

Put up a sheet of paper (blank) at 100 yards. About 48" square would be fine but as big as you have is grand. Find the dead centre of the sheet of paper. Place a half inch black dot in the centre. This is your aim point. You want no other markings on the paper to distract you. You need to be very careful that its 100 yard and no more or less than 100 by a yard. Most scopes click values are designed to work at 100 yards so you really need to be sure of the distance. Fire a couple of shots, and make sure you are in the bull with each one, and your zero is perfectly on for 100. That means not an inch high, or low.

Once you have the "perfect" zero put up a fresh target or if they are all in the black dot you can use the same sheet. Again making sure its still as bang on for 100 yards as possible. Now dial up 10 MOA (40clicks) on the scope. If the scope is worked in 1 click = 1cm @ 100 yads dial on 25clicks. That'll give you 25cm or roughly 10 inches. Aim at the bullseye and fire.

Now dial right 10 MOA (for 0.25 click valus scope) or 25 clicks (for 1cm per click). Again aim at the bullseye, and fire.

Now dial down 20 MOA (80 clicks in a 0.25 clcik value scope) or 50 clicks (if the scope is 1cm per click ). Aim at the bullseye and fire.

Now dial left 20 MOA (80 clicks in a 0.25 clcik value scope) or 50 clicks (if the scope is 1cm per click ). Aim at the bullseye and fire.

Now dial up 20 MOA (80 clicks in a 0.25 clcik value scope) or 50 clicks (if the scope is 1cm per click ). Aim at the bullseye and fire.

It's important you only fire 1 shot per adjustment. Measure the distances from holes to holes. The holes of the bullets should "draw" a perfect (within a half an inch for human error) square. You should have something like this:




The problem, as i touched on above, with all these tests is:

• Shooting position/platform
• Ammo
• Weather conditions
• Shooter ability
• Rifle ability

If any of these is not "at it's best" then results may not be accurate, but it's still possible to do the tests and get a rough idea of your scopes ability.[/QUOTE]

Of course the simple and most obvious solution would be as you said cookie, that there is an issue with the threading on the rings and this is causing the issue.

Could be. For European rifles it's always 9-11 mm.

Another solution i was thinking of was buying a set of 9-11mm dovetail to picatinny adaptors and then buying picatinny rings to suit.