Depending on how you set up your AR15, there are two common options when choosing the best scope for your AR15: Low-Power Variable Optics and SPR Optics.
Low-Power Variable Optics include scopes that have a minimum magnification of 1x. In most cases, these scopes can magnify up to 6x, 8x, or even 10x for some premium models. Most 5.56 AR owners optimize their setup for close-range to medium-range, so a low-power scope allows greater flexibility when engaging targets in close quarters. The marksman can easily transition to a higher magnification when taking precision shots at a distance. LPVOs are relatively lightweight, and with many optic manufacturers offering a wide variety of competitive models, you can always find excellent performance for any budget.
If your AR15 is more precision-oriented, or if you’re using a caliber like .224 Valkyrie or 6.5 Grendel, you might want an optic with more magnification. Scopes with a 2x, 3x, or 4x minimum magnification will usually offer a solid balance of medium- and long-distance performance without compromising on weight and size. For these special precision rifles, we recommend keeping your maximum magnification under 15x. Very few intermediate cartridges can perform well beyond the 1000-yard line, so any additional magnification is mostly overkill.