From what you have said (and not said) I presume that you have an AR15A2, not an A3 with the detachable handle. If you have an A2, DO NOT attempt to remove the front sight "delta". This is not just the sight base, but the gas block. If you remove the front sight base, you risk damaging the "gas bleed" system! As was mentioned, your front sight will barely be noticeable in the scope, and may appear as nothing more than a slightly distracting "blur".
My advice, is that IF you want a sight picture without the blur of your front sight base, consider purchasing a second complete AR barreled upper. By doing this, you can have an upper with a "clean" A4 profile, with the built in picatinny rail on the upper and gas block, that you can place QD sights on, and still have original upper. Additionally, chances are VERY good, that your current AR has a 1:9" barrel, unless you have a competition model (with either a 1:7" or 1:8" twist). If you purchase a new upper unit, you can have either a 1:8" or 1:7" barrel. The benefit of a different barrel will be seen in range and accuracy. With the 1:9" barrel, the heaviest bullet you can expect to shoot accurately would be UP TO 69 grains, at perhaps 300 yards, but subject to the wind. If you go to a 1:8" or 1:7" barrel, you can shoot 77s very accurately at 300, and 80s (single fed) extremely well at 600 yards. The 80s in a 1:8" barrel can give accuracy comparable to an M14/M1A/M21 shooting M852/M118/XM118 out to a 1000 yards. If you can find an AR barrel that has a 1:6.5" twist, you can fire 90s extremely well at 1000 yards.
The problem with using a build-up base on your scope mount, is that in order to have a good sight picture (sight alignment), you will have to raise your cheek above the stock comb, destroying your stock weld and affecting your accuracy.
Good luck and good shooting!
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