AR15 11.5 vs 12.5 – Does 1″ Difference Really Matter?

AR15 11.5 vs 12.5 barrel length. Does it really matter that much? Among AR15 builders, the comparison between 11.5 inch and 12.5 inch barrels sparks a lot of discussions.

Long story short, for casual users who only visit 25 yard ranges, none of it matters.

Some of the most important difference to consider are:

  • Muzzle velocity
  • Gas port sizes
  • CQB performance accounting for muzzle device length

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12.5 Inch Barrel Advantages

12.5 ar15

For users who want to optimize their setup. The 12.5 inch barrel for its ability to accommodate a mid-length gas system. This often means smoother operation compared to the carbine-length systems typically used with shorter barrels.

mid length gas system

This extra inch allows for more dwell time—the period between the bullet passing the gas port and exiting the barrel—resulting in a softer shooting experience if using all standard AR15 accessories without muzzle brake or highly optimized recoil springs.

As far as ballistic performance goes the 12.5-inch barrel offers a slight advantage in muzzle velocity, which can be significant depending on the ammunition used. For instance, velocity tests on specific setups have shown increases ranging from 50 to 230 FPS when comparing 12.5-inch barrels to their 11.5-inch counterparts. This increase in velocity can enhance ballistic performance, extending the effective range and improving terminal ballistics.

11.5 Inch Barrel Advantages

11.5 ar15

On the other side of the debate, the 11.5 inch ar15 barrel has its own set of advantages. Its shorter length makes it more maneuverable, which is a critical factor for close-quarters scenarios or for those prioritizing a compact setup.

Despite the slight reduction in velocity compared to the 12.5-inch barrel, the 11.5-inch barrel still delivers adequate performance for most practical applications, especially in urban environments where engagement distances are typically short.

556 bullet velocity vs barrel length

Some users argue that the difference in shooting smoothness between the two lengths can be mitigated through proper tuning. Adjustable gas blocks, buffer systems, and carriers can fine-tune an 11.5-inch setup to achieve a shooting experience that rivals the 12.5-inch barrels.

Additionally, for those looking to minimize the overall length of their AR15, especially when adding a suppressor, the 11.5-inch barrel offers a shorter base platform.

ar15 pov red dot

Personal Preference

Ultimately, the choice between 11.5" and 12.5" barrels largely comes down to personal preference, especially when using 55 gr ammunition. The ballistic differences are minimal for close-quarters combat (CQB) situations.

For those considering suppressor use, the 11.5" barrel might be more suitable, although suppressors vary in size and length.

dirty ar15

With the vast array of AR15 customization options, including ammo types, buffer springs, gas tubes, barrel gas port sizes, lengths, twist rates, and suppressor designs, the overall performance is influenced by more than just barrel length.

At the end of the day, cost is a big factor to most buyers in today's economy. Whatever is available and affordable, buy it without nitpick performance specs that really doesn't matter.

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