Vision king 10 - 40 x 56. New scope query

[Henry Martini]

Not sure if this is the correct forum section, if not please advise and I will move it.
Down at the range today with a club member who had just bought a brand new Vision king 10 - 40 x 56 mm scope with the intention of using it on the 100 yard range.
Set it up on 50 metres at 12 magnification, as previous scope and achieved the v bull, 15 mm diameter, consistently.
Decided to increase the magnification in units of 5 from 15 x to 40 x magnification.
15 x magnification OK, but would not focus at 20 x magnification. The best that could be achieved was 18 x magnification. Blades of grass became a blur.
Cannot understand why it was OK at 15 x magnification but no higher.
Can anyone offer any guidance or advice on what else can be tried as these higher power scopes are not something we have used before and there may be something that we should have done.
Regards, HM

[Hurricane]

It will have a minimum focus distance, at lower mags this won't have much effect as the DoF will be large, but as the mag increases the DoF decreases and you can't focus. Try it at 100yds and it will probably be fine.

[Jesim1]

You get what you pay for with glass - a Big Nikko will easily focus at x50 mag on a 20m target - probably less, but I've never tried it at less as x50 is too high for me at that range let alone closer, but it did work It sounds like this scope is not designed with air gunners in mind and they have concentrated on distance for the clarity they can get for the money

[Henry Martini]

Reset the scope settings to 100 yds and focused on neighbours' chimneys and television aerials, after covering/disguising the rifle!
Et voila, everything in focus at increasing magnifications.
Next step is to do the business on the range.
Thank you very much for your advice, it was most useful.
Regards, HM

It will have a minimum focus distance, at lower mags this won't have much effect as the DoF will be large, but as the mag increases the DoF decreases and you can't focus. Try it at 100yds and it will probably be fine.

[loiner1965]

Reset the scope settings to 100 yds and focused on neighbours' chimneys and television aerials, after covering/disguising the rifle!
Et voila, everything in focus at increasing magnifications.
Next step is to do the business on the range.
Thank you very much for your advice, it was most useful.
Regards, HM

done that a few times with the rifle pointing between the bedroom blinds......looking like a japanese sniper ( not at bedrooms for the lesser minded folk on here )
having rifles can be such a pain at times when you have to mind what you say or do

[JerryD]

These scopes are meant to have adjustable sidewheeln parallax down to 12yds: is said club member actually adjusting the parallax at all?



.

[Henry Martini]

On the 100 yds range today and after adjusting a range of settings achieved a group of 5 within 3/4".
Achieved this on 20 x magnification and a Caldwell front rest. Although the scope may be capable of use on a fullbore rifle it will only be used on the 50 metres and 100 yds ranges. So maybe the scope is over specified but the price was acceptable and a significantly lower cost than
on that well known internet auction site.
Regards, HM.