Just looking for a simple explanation in ref to these types of mounts.I have a remington 700 and would like to use these to mount a scope. I understand the short and long action but what do they mean by and when should each type be used ? Example i have seen, standard,20moa,25moa,30moa and i thought i saw 40and 15 moa. Open to all ideas.

As you mentioned, short or long for action length, but the MOA reference is referring to how many minutes of angle is gained w/ whichever base you may select. All these bases do is raise the rear of the scope to provide you with more elevation adjustment than perhaps the actual scope has built into it. Normal, whatever that is, sporting/hunting scopes will have some 40-60moa elevation adj. and if you are attempting to shoot long range, say more than 600 yards, you will run out of elevation w/ the scope and using one of these bases as you mention will give you more elevation. Tactical type/30mm tube scopes will often have close to if not more than 100moa avaialbe without the base.
One other advantage to the picatinny rail system is that you can mount your optics further forward and this is important if shooting prone for you will need to get the scope further away from your eye in order to see the full field of the scope. If you are shooting from rest/bipod, etc., not as important, but with sling definitely will need to get that scope moved forward. Good rule of thumb is to have the eyepiece somewhere near in line with the bolt shroud. It will vary with different brands of scopes.

Thanks for your input,but should a person use a different moa for different distances like 500 yards and under compared to 500 yards and up. Thats where i am also asking for help so i decide on the one for my needs. The remington is a 700 model in a 257 roberts and i have a 3x9 leopold to put on.

Unless you are going to shoot at ranges greater than say 600yds I see no reason for any additional base for your rifle. A way to determine if your scope/base/rifle will "reach" a target of say 600yds, would be as follows:
Zero rifle at 100yds. Rotate elevation drum
/dial to it's bottom and count the number of clicks/notches it takes to bottom out. Bring back up that number of clicks to put you back on at the 100yd zero. I would guess that you have used some 12-18 minutes of angle to return to your 100yd zero(if 1/4moa clks then you would have moved some 48-72clks.) Most likely it will take you some 15 minutes(60clks)more to reach the 600yd line. If that be the case, then you can determine how much of the elevation adj. you have consumed in reaching a distance of 600. Would guess your scope may have a maximum elevation range of some 60 minutes of angle and you would still have some elevation adj. left, but not suffecient to reach beyond the 800yd line. Probably a good idea if you do not know the elev. range of your scope is to botom out, click as high as it will go and count the clicks. Rough rule of thumb is that out to the 700yd line, approx. 3 moa per hundred or once on at 100 and you want to reach 600 yd line, 5x3 or 15 more minutes. Don't know if I have helped or confused, but again, don't think you need any additonal base unless you are wanting to go beyond the 600yd line.

Than if i want a scope mounting system that has more flex options stay with the picatinny rail and stay with zero raise factor if i will be shooting less say a max of 600 yards or less for deer/varmints. How does that sound? If a am wrong feel free to give me a blast before i order.n fact let me know if i am right.

Hello,
You have made the correct assumption. Zero elevation base, yet has more options of positioning the scope itself. For your purposes, the elevation is not needed.

martin

Make sure the picatinny rail meets 1913 mil specs. Badger makes a great one. I have one of their zero taper bases on my 700 CDL.