differences between picatinny, dovetail , weaver rail

[kaka brar]

Hello friends .. hope you enjoying shooting your airguns
This is my first post on ifg though i alteady read most of the posts from other people here ..
So my query is regarding air rifle mounts
I often hear about this picatinny , dovetail, weaver rail,
Whats the difference between these things
And my second query is regarding buying scope mounts for a scope i recently bought. Its 3-9x40 scipe with 20mm dovetail mounts and the scope tube being 25.4 mm or 1inch .. NOW THE PROBLEM I AM FACING IS THAT MY GUN PRECIHOLE Nx .22 has dovetail 11mm but these are for 20mm dovetail ..
Friends please suggest me what should i do
Should i buy 11mm scope rings or opt for 11mm to 20mm converter .. I have also heard that mounting scope on a dovetail with just scioe rings is often not a rigid system and suffers scope shifts .. is it true ?
What is the perfect solution for the rigid fixture of this scope for my precihole gun .. what should i further buy , a adapter or rings or wht ?
Please guide me friends ...
Thanks already for the useful topics ..

[Chengy]

Ok..to clear your confusion..Dovetail (11mm) is totally different from the other two (weaver and picatinny) and is generally used for airguns and rimfire rifles like 0.22. It also comes in other sizes like 9 mm, 16 mm etc.. Picatinny (20 mm) is a military standard mount generally used on assault rifles and the like. A weaver mount (mostly used for civilian center fire rifles like 30.06 etc ) will fit on a picatinny but not vice versa. I would advise you to buy good quality dovetail ring mounts for your scope. Sportsmach (UK) makes good 11mm mounts. You could use an adapter but then you are increasing the chances of the scope working loose. Hope this helps. regards