All About AR-15 Sights

There’s more to know about iron sights than you might imagine!

by Joe Carlos

One of Bill Clinton’s “crowning achievements” (when he could spare time from his sexual dalliances) was passage of the Federal Assault Weapons Ban. In the hoplophobic minds of its authors, flash suppressors and bayonet lugs were evil talismans that could change normal people into dangerous sociopaths. Cosmetically-altered versions of the black gun missing these were known as “Post Ban” models and those having them were “Pre Ban.” There was a sunset on this law and it expired but some states enacted similarly useless laws still on the books. A few shooters found that they liked Post Ban configurations better. The most common practice for gunsmiths building ARs without flash suppressors is to use front sight housings sans bayonet lug. I have had a few such “mix and match” (or “mismatch”?) examples come in my shop and it doesn’t degrade performance either way, though I feel having one but not the other appears tacky. Deal with that as you see fit.

Front Sight Mounting

The old school way of mounting a front sight was with taper pins driven in at the factory by gorrillas, the way the military still fastens theirs. Unfortunately, this practice has a negative impact on accuracy. Anything done on the outside of any gun barrel can influence the internals, more so in hammer forged or button rifled barrels which do not cut out the grooves but simply swage metal to form the grooves. Military M16 barrels are button rifled and the same factories normally hammer forge machine gun barrels. When the taper pins are hard driven in place they tend to constrict the bores of the barrels slightly and bullets passing such constrictions are boogered twice rotating past each each pin. Bullets twice deformed on different sides don’t shoot accurately.

It’s not difficult to remove some of this bore constriction, as described in “Improving Rack-Grade AR-15s” (December 2014.) Because of the justifiable bad reputation tapered pins have earned regarding accuracy degradation, some barrel manufacturers have made an effort to either improve or obfuscate (depending on your point of view) matters by changing to straight pins. Whether these really deform the internals of a gun bore less is something I have never attempted to quantify but I will say that they are highly suspect. The techniques in my previous article can be modified to work with straight pins. If you are selecting a barrel for serious target shooting I wouldn’t use any barrel with a pinned front sight. These are normally offered by low bid, lower quality barrel manufacturers, starting with a poor quality barrel blank and risking worsened accuracy by pinning the sight in place. On the other hand, if you are building a “minute of tin can” blaster, save money by choosing such a barrel.

Read more in our August 2015 issue.

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